Showing papers in "The Auk in 1987"

Unrepeatable repeatabilities: a common mistake

Abstract: -Repeatability is a useful tool for the population geneticist or genetical ecologist, but several papers have carried errors in its calculation We outline the correct calculation of repeatability, point out the common mistake, show how the incorrectly calculated value relates to repeatability, and provide a method for checking published values and calculating approximate repeatability values from the F ratio (mean squares among groups/ mean squares within groups) Received 6 February 1986, accepted 25 August 1986 REPEATABILITY is a measure used in quantitative genetics to describe the proportion of variance in a character that occurs among rather than within individuals Repeatability, r, is given by: r = (VG + VEg)/ VP, (1) where VG is the genotypic variance, VEg the general environmental variance, and Vp the phenotypic variance (Falconer 1960, 1981) In addition to its use in assessing the reliability of multiple measurements on the same individual, repeatability may be used to set an upper limit to the value of heritability (Falconer 1960, 1981) and to separate, for instance, the effects of "self" and "mate" on a character such as clutch size (van Noordwijk et al 1980) Repeatability is therefore a useful statistic for population geneticists and genetical ecologists Recently, we have noticed an increasing number of published papers and unpublished manuscripts in which repeatability was miscalculated Our purpose is fivefold: (1) to outline the correct method of calculating repeatability; (2) to point out a common mistake in calculating repeatability; (3) to show how much this mistake affects values of repeatability; (4) to provide a quick way of checking published estimates, and to calculate an approximate value of repeatability from published F ratios and degrees of freedom; and (5) to make recommendations for authors, referees, editors, and readers to prevent the promulgation and propagation of incorrect repeatability values in the literature CALCULATION OF REPEATABILITY Repeatability is the intraclass correlation coefficient (Sokal and Rohlf 1981), which is based on variance components derived from a one-way analysis of variance (ANOVA) The intraclass correlation coefficient is given by some statistical packages; otherwise it can be calculated from an ANOVA ANOVA is described in most statistics textbooks (eg Sokal and Rohlf 1981; Kirk 1968 gives a detailed treatment of more complex designs of ANOVA), so we will not repeat it here, but give the general form of the results from such an analysis in Table 1 Repeatability, r, is given by r = sA / (S + SA)' (2) where S2A is the among-groups variance component and s2 is the within-group variance component These variance components are calculated from the mean squares in the analysis of variance as:

Effects of Experimental Manipulation of Testosterone Levels on Parental Investment and Breeding Success in Male House Sparrows

Abstract: -Breeding male House Sparrows (Passer domesticus) were implanted with testosterone (T), the antiandrogen flutamide (F), or an empty capsule as a control (C). Parental feeding rates by C-treated males were high until nestlings reached 10 days of age, then declined significantly. This is the typical temporal pattern of parental behavior for free-living males. In contrast, F-treated males fed young at a high rate throughout the nestling stage, while T-treated males fed young much less frequently and were more involved in male-male competition during this period of time. There was a significant decrease in the breeding success of T-treated males resulting from increased starvation of their nestlings. Despite lowered levels of testosterone, F-treated males were able to maintain control of their nest boxes and exhibited normal sexual behavior. During the subsequent brood, breeding success of T-treated males again was reduced by nestling starvation. Our results demonstrate that high levels of testosterone inhibit the expression of parental care in male House Sparrows. Moreover, they suggest that the typical pattern of testosterone levels in males (high when mate guarding and low when feeding young) represents an optimal compromise between allocation of effort to male-male competition vs. parental care. Received 10 July 1986, accepted 1 March 1987. CORRELATIONAL and experimental studies on House Sparrows (Passer domesticus) have suggested that the activities of breeding males represent a trade-off between investment in malemale competition vs. parental care. In males, circulating levels of testosterone reflect this trade-off, being elevated when male-male competition is high and low when parental investment is high. We have suggested that this pattern maximizes an individual's overall reproductive output, even if it results occasionally in a reduction of fecundity (Hegner and Wingfield 1986a, 1987). In this study, we tested experimentally whether the variable pattern of male investment represents an optimization by artificially altering that pattern. This was achieved by altering the endocrine and behavioral state of males with subcutaneous hormone implants. We tested specifically whether elevated levels of testosterone during the last portion of the nestling stage, the interbrood interval, and the egglaying stage are critical for (1) defense of the I Present address: Department of Zoology, NJ-15, University of Washington, Seattle, Washington 98195 USA. nesting site, (2) normal sexual behavior, and (3) successful mate guarding. We also tested (4) whether lowered levels of testosterone during incubation and the early portion of the nestling stage are necessary for the expression of parental care.

Effects of nestling diet on growth and adult size of Zebra Finches (Poephila guttata)

Abstract: Manipulation of the diet of Zebra Finch (Poephila guttata) nestlings in the laboratory showed that a low-quality diet reduced growth rates of nine external morpholog- ical characters, while a high-quality diet increased growth rates. The growth of plumage characters was least affected by diet, while growth rates of tarsus and mass were most af- fected. The treatments also produced differences in the adult size of experimental birds, differences not evident in either their parents or their own offspring. Diet quality had the strongest impact on adult mass and tarsus length, while plumage and beak measurements were less affected. Analysis using principal components and character ratios showed that the shape of experimental birds was affected by the experimental diets, but to a minor extent compared with changes in overall size. Significant shape changes involved ratios between fast- and slow-growing characters. The ratios of characters that grow at similar, slow rates (e.g. beak shape) were not affected by the diets. Environmental sources of morphological variation should not be neglected in studies of phenotypic variation in birds. Received 5 June 1986, accepted 30 October 1986. MORPHOLOGICAL differences between indi- vidual birds are often assigned functional sig- nificance, whether those individuals are of dif- ferent species, different sexes, or different-size members of the same sex (Hamilton 1961, Se- lander 1966, Clark 1979, James 1982). In grani- vores such as Darwin's finches (Geospiza spp.), morphological differences have been related to variation in feeding efficiency at all three of these levels. Differences in feeding efficiency have in turn been correlated with variation in fitness due to spatial or temporal variation in seed availability (Boag and Grant 1981, Schlu- ter and Grant 1984). Intraspecific morphologi- cal variation in several species, such as House Sparrows (Passer domesticus; Johnston and Se- lander 1971), Red-winged Blackbirds (Agelaius phoeniceus; Power 1969), Great Tits (Parus major; Hamilton 1961), and others (James 1970) has been correlated with clinal variation in cli- mate. A classic example of the correlation be- tween intraspecific morphological variation, fitness, and weather was seen in the nonran- dom survival of House Sparrows collected by Hiram Bumpus following a winter storm

Energy-expenditure during free flight in trained and free-living eurasian kestrels (falco-tinnunculus)

Abstract: -During directional flight trained Eurasian Kestrels (Falco tinnunculus) in the laboratory expended 13.8 W. Free-living birds expended 14.6 W during nonsoaring flight that included both directional flight and wind hovering. The former value was obtained by combining food balance and indirect calorimetry techniques, the latter by doubly labeled water (D2180). Because the energy-expenditure rates are so similar for directional flight alone and for wind hovering and directional flight combined, we argue that the value for either mode of kestrel flight may be used to analyze time-energy budgets. We predicted avian flight costs (ef) from an equation based on published data on flight costs in 14 species (body mass 3.8-1,000 g): ef = 17.360M1 013b0 -4236S, 1.926 W where M is body mass (g), b, is wing span (cm), and sw is wing area (cm2). Inclusion of the morphological data with body mass significantly improved the prediction of flight cost [r2 = 0.84 vs. r2 = 0.75 without b, and sw, F, (2,18) = 5.34, P < 0.05]. Received 8 May 1986, accepted 29 November 1986. QUANTIFICATION of the components of daily energy expenditure will improve the understanding of the behavior of free-living birds. This can be achieved by combining time-activity budgets with estimates of the various cost factors (e.g. basal metabolism, thermoregulation, flight; Koplin et al. 1980, Mugaas and King 1981). Energy expenditure during flight is increased greatly relative to during other behaviors (e.g. Berger and Hart 1974). Therefore, even though little time may be devoted to flight, an error in the estimate of the flight cost will produce a considerable error in the total daily energy expenditure estimated from time-activity models. Available allometric equations that predict flight cost in birds are based solely on body mass (e.g. Berger and Hart 1974, Kendeigh et al. 1977, Butler 1980) and provide only a rough estimate of power consumption. Energy expenditure during flight varies among birds of the same mass, according to flight pattern and the aerodynamic and behavioral properties of the species (Nisbet 1967, Utter and LeFebvre 1970, Hails 1979, Dolnik 1982, Flint and Nagy 1984). The Eurasian Kestrel (Falco tinnunculus) has two distinct modes of powered flight: (1) directional flapping flight and (2) wind hovering, which is flapping flight against the wind with zero ground speed (Videler et al. 1983). We determined energy expenditure in kestrels during powered flight. We used this information to quantify total daily energy expenditure of the Eurasian Kestrel throughout its annual cycle (Masman 1986). We used two techniques to determine flight cost. The energy budgets of trained, free-flying kestrels in the laboratory were reconstructed by monitoring daily metabolizable energy intake, oxygen consumption during rest, and time spent flying per day, from which the energy expenditure during directional flight was estimated. In the field we measured daily energy expenditure of free-living kestrels by a doubly labeled water (D2180) technique (Lifson et al. 1955). Time spent flying was recorded simultaneously. Energy expenditure during combined directional flight and wind hovering was estimated from the correlation between daily CO2 production and time spent in flight.

Competitive interactions within and between species in a guild of Avian scavengers

Abstract: -We observed Andean Condors (Vultur gryphus), King Vultures (Sarcoramphus papa), Black Vultures (Coragyps atratus), Turkey Vultures (Cathartes aura), and Crested Caracaras (Polyborus plancus) interacting at 217 animal carcasses at two sites in northern Peru. At 53 carcasses for which we knew order of arrival, Turkey Vultures usually arrived first, Black Vultures second, and condors third. On the basis of our observations of 8,066 aggressive encounters between birds, we constructed dominance hierarchies by calculating the proportion of encounters won by an individual of one species, sex, or age during encounters with an individual of another species, sex, or age. Within each species there was a positive relationship between a bird's dominance and its age. In condors, males dominated females of the same age. Interspecific dominance was correlated positively with body mass. There are convergent similarities between the organizations of guilds of Old and New World vultures. Received 1 August 1986, accepted 24 November 1986. WHEN limited resources are found in Widely dispersed, rich patches that are ephemeral and unpredictable in spatial and temporal occurrence, competition between consumers could involve either differential exploitation or interference. Differential exploitation in such situations is often based on the differential ability of individuals to locate the resource, and interference usually is achieved through the establishment of dominance hierarchies among individuals that have found the resource (Maurer 1984). Avian scavengers that feed on carcasses of large animals compete for just such a limited, dispersed, rich, ephemeral, and unpredictable food source, and differences in order of arrival at carcasses and dominance hierarchies when birds are feeding together have been reported among members of scavenging guilds (Kruuk 1967, Houston 1975). The most detailed studies of competitive interactions between avian scavengers have taken place in Africa where large guilds of Old World vultures (Accipitridae) feed on ungulate carcasses (Petrides 1959; Attwell 1963; Kruuk 1967; Houston 1974, 1975). In contrast, there have been few descriptions, most of them anecdotal accounts (e.g. Koford 1953, Stuart 1978), of competitive interactions in guilds of New World vultures (Cathartidae). We observed patterns of differential exploitation and interference within and between 5 species that are competing members of a guild of avian scavengers in northern Peru: Andean Condors (Vultur gryphus), King Vultures (Sarcoramphus papa), Black Vultures (Coragyps atratus), Turkey Vultures (Cathartes aura), and Crested Caracaras (Polyborus plancus). We have shown previously that during our study several of these species were being limited by the availability of carrion during a prolonged preEl Nifio drought (Wallace and Temple 1987). STUDY AREA AND METHODS The field observations took place between 1980 and 1984 in northern Peru in the Cerro Illescas region and in the vicinity of Naupe. The Cerro Illescas is an isolated mountain range of the Sechura Peninsula (6.0?S, 81.0?W). Avian scavengers in this study area fed almost exclusively on the carcasses of either marine birds and mammals that washed ashore on the peninsula's beaches or feral ungulates that died in the surrounding desert. The Naupe area is about 150 km east of the Cerro Illescas in the western foothills of the Andes (5.35?S, 79.4?W). Avian scavengers in this study area fed primarily on carcasses of domestic livestock that died on the area's desert grasslands. In both areas we observed birds interacting at 217 carcasses of large animals at as many sites: 129 burros (Equus asinus), 57 dogs (Canis domesticus), 12 sea lions (Otaria byronia), 10 goats (Capra hircus), 4 horses (Equus caballus), 4 pigs (Sus scrofa), and 1 green sea turtle (Chelonia mydas). Each of these carcasses was sufficiently large to be highly attractive to all members of the guild. We opened the largest carcasses so that they could be consumed by all guild members. If we had not done this, smaller vultures would have been forced to wait until larger birds had first ripped the thick-skinned carcasses open. We watched these carcasses for a total of 4,071 h from blinds positioned 290 The Auk 104: 290-295. April 1987 This content downloaded from 157.55.39.45 on Thu, 01 Sep 2016 05:57:50 UTC All use subject to http://about.jstor.org/terms April 1987] Competition Among Avian Scavengers 291 8 141 17 53 1.0 132 0 0 0 >_ 0 m~~~~~~~~~

Intraspecific variation in migratory pattern of a partial migrant, the Blue Tit (Parus caeruleus): An evaluation of different hypotheses

Abstract: To evaluate hypotheses explaining intraspecific variation in migratory behavior in partial migrants, a local population of Blue Tits (Parus caeruleus) was studied in southern Sweden. Birds born in the study area and recaptured there in winter were compared with birds recaptured at a nearby bird station where a large number of migrant Blue Tits were passing. By comparing sex ratios among migrants and residents, we concluded that, among juveniles, more than 40% of the females and a significant proportion of the males migrated, while considerably fewer adult females and virtually no adult males did so. Migrant and resident Blue Tits did not differ in size as nestlings, but more late- than early-hatched males migrated. No differences in hatching date were determined for females, presumably because most of them migrated. Our findings are consistent with the "dominance hypothesis" as an explanation of partial migration, i.e. that the individuals lowest in rank migrate. The fitness gain that leads dominants to stay as residents may be lower winter mortality or a higher probability of establishing a territory in spring. In either case, keener competition for breeding territories among males than among females as a cause tor higher residency cannot be excluded. (Less)

Release of captive-reared or translocated endangered birds: What do we need to know?

Abstract: dangered or nonendangered species. Although many programs have attempted to establish or augment wild populations with captive-reared or wild-caught birds (Williams 1977), there are few published accounts that allow quantitative statements on the success of releases and the role played by animals subjected to different rearing and release protocols (Berger 1978, Kear and Berger ! 980). This makes it difficult to assess accurately the status of these species, or to evaluate the influence of various management actions. The U.S. Fish and Wildlife Service (hereafter USFWS) lists 220 taxa of birds as threatened or endangered (USFWS 1986). Recovery plans exist for 45 of them. Captive rearing is cited frequently in recovery plans as a requirement to ensure the recovery of these species. Captive rearing of species with release to the wild is an important management technique used in attempts to save species from extinction (Martin 1975, Temple 1978, Carpenter and Derrickson 1981, Carpenter 1983). Reintroduction generally is initiated only after more conservative techniques (e.g. habitat protection, law enforcement, and public education) have been unsuccessful in restoring population levels. Captive propagation is viewed by many as the last possible action appropriate for only a few select species (Conway 1978, Scott et al. 1986a, Temple 1986). Potential benefits of reintroduction programs include (1) increasing the number of animals in a small population, (2) increasing genetic diversity in a small population, (3) reducing inbreeding depression in small populations, and (4) establishing new populations.

Effects of brood-size manipulations on parental investment, breeding success, and reproductive endocrinology of house sparrows

Abstract: -Brood sizes of House Sparrows (Passer domesticus) were altered experimentally by adding or subtracting 2 nestlings. Unaltered broods served as controls, and experimental brood sizes were within the normal range found under natural conditions. Feeding rates of both parents increased with brood size, and although nestling mass decreased with brood size, most pairs were able to fledge the extra young added to their broods. Males rearing larger broods invested less in nest-site defense and mate-guarding activities, and females rearing larger broods took longer to initiate subsequent broods and produced smaller subsequent clutches. However, the productivity of the subsequent broods did not decrease. Adult survivorship was not affected by the brood manipulations. In males, circulating levels of dihydrotestosterone increased significantly with brood size. Levels of other hormones, including luteinizing hormone (LH), testosterone, estradiol-17#, and corticosterone (B), were not related to brood size in either sex, although in females LH and B titers tended to increase with brood size. Males feeding larger broods tended to have less body fat, but otherwise there was no relationship between brood size and body condition. These results suggest that adults tending larger broods were not unduly stressed by their extra efforts, at least when feeding nestlings. However, the increased interbrood interval and decreased subsequent clutch size associated with rearing larger broods may have resulted either from the increased energetic and nutrient demand on females after the young fledged or simply from the extra time required to rear the additional fledglings to independence. Received 10 July 1986, accepted 1 March 1987. IMPLICIT in many discussions of life-history phenomena is the assumption that organisms trade off two or more conflicting activities in a manner that maximizes their overall reproductive output (e.g. Williams 1966, Charnov and Krebs 1974). For example, most iteroparous organisms are assumed to forgo maximum annual productivity to increase subsequent survivorship, thereby maximizing lifetime fecundity (e.g. Kluyver 1963, Williams 1966, Charnov and Krebs 1974). Moreover, even within a given breeding season, other trade-offs may occur (e.g. McGillivray 1983). For males, Trivers (1972) proposed a fundamental trade-off between competing with other males to fertilize the ova of females and providing parental care to the offspring they produce. Ecological restrictions on these two options have been used to explain mating systems (e.g. Emlen and Oring 1977). We have suggested that endocrine and associ1 Present address: Department of Zoology, NJ-15, University of Washington, Seattle, Washington 98195 USA. ated behavioral changes of monogamous male House Sparrows (Passer domesticus) during the breeding season reflect a compromise between these two options (Hegner and Wingfield 1986a). In our study area, a given pair of House Sparrows may attempt from 3 to 5 broods within a nesting season. In adults, circulating levels of reproductive hormones vary considerably during different stages of nesting. Plasma concentrations of luteinizing hormone (LH), androgens, and estrogens are maximum during the egg-laying stage of each brood, decline rapidly during incubation, remain low after the young hatch, and rise again as the young approach fledging. In females, rising levels of LH and estradiol (E2) following fledging are indications of physiological preparation for laying the next clutch (Hegner and Wingfield 1986b). In males, levels of LH and testosterone rise rapidly to maximum concentrations when nestlings reach 9-10 days of age, well before the young fledge (typically when 14-15 days old). This reflects a transition between a state of high investment in parental care, when testosterone levels are 470 The Auk 104: 470-480. July 1987 This content downloaded from 157.55.39.4 on Fri, 09 Sep 2016 04:28:40 UTC All use subject to http://about.jstor.org/terms Julv 19871 Brood Manipulations in House Sparrows 471 low, to one of high investment in male-male competition, when testosterone levels are high (Hegner and Wingfield 1986a). We examined the physiological and reproductive effects of altering the demand for parental care on free-living House Sparrows. For some pairs we increased the demand for parental care by adding two young to the nest, for others we decreased that demand by removing two young from the nest, and for a third group the number of nestlings was unchanged. We subsequently determined the effects of these manipulations on investment in parental care, investment by males in male-male competition, circulating levels of reproductive hormones, body condition, breeding success in the experimental and subsequent broods, and adult survival to the next year.

Habitat Use by Wading Birds in a Subtropical Estuary: Implications of Hydrography

Abstract: -The dynamics of foraging habitat use by long-legged wading birds was analyzed with respect to water-level fluctuation patterns in Florida Bay. Wading-bird presence at four sites situated to sample the heterogeneity of the bay was quantified by repeated surveys collected throughout the day and year. Models for habitat availability were generated using water-level data collected from continuous recorders, staff gauges, and habitat profile maps. These models were tested against the survey data. Roseate Spoonbills (Ajaia ajaja) foraged on the study areas primarily at night. Great Blue Herons (Ardea herodias) fed both day and night, but primarily at night where the tidal range was small. Great Egrets (Casmerodius albus), Snowy (Egretta thula) and Reddish (E. rufescens) egrets, Little Blue (E. caerulea) and Tricolored (E. tricolor) herons, and White Ibis (Eudocimus albus) fed during daylight. Where tidal range was small (< 5 cm) diurnal species fed throughout the day. Florida Bay has a pronounced annual water-level cycle that causes monthly mean water levels to vary by as much as 30 cm between October (high) and May (low). Models derived from hydrology data predicted that this seasonal variation in water level would have a major impact on habitat availability, particularly where tidal flux was small. The predictions were supported by survey data. At sites with minor tides, most wading-bird species had a cycle in seasonal abundance that correlated with seasonal changes in water level; only the tallest species, Ardea herodias, was uniformly present throughout the year. The large daily range in tide (xf = 80 cm) afforded year-round access to foraging habitat, and these abundance patterns did not exist. The seasonal variability in habitat availability has major management implications because the maintenance of stable wading-bird populations depends on the availability of alternative foraging sites when water levels are high. Historically, these sites have tended to be targeted for human development. Received 20 October 1986, accepted 11 June 1987. THE dynamics of foraging habitat use by wading birds have been well studied for shortlegged waders (Charadriiformes; Goss-Custard 1970, Holmes 1970, Burger et al. 1977, GossCustard et al. 1977, Silliman et al. 1977, Myers 1980, Connors et al. 1981, Fleischer 1983) but are poorly known for long-legged species (Ciconiiformes). This is especially true for marine systems, where studies have focused on major environmental cycles (see Kushlan 1981 for review). Ciconiiformes (hereafter "wading birds") are known to alter their feeding-site selection in relation to major seasonal climatic changes (Ryder 1967, 1978; Henny 1972) and the lunar tidal cycle (Krebs 1974, Brandman 1976, Bayer 1978, Custer and Osborn 1978a, Pratt 1980). Beyond the patterns imposed by these major cycles, little is known about the dynamics of habitat use by wading birds. In marine and estuarine ecosystems of southern Florida, where seasonal variations in the annual temperature cycle are relatively minor and the lunar tidal range tends to be small (NOAA tide tables 1986), habitat use by wadingbird populations is potentially independent of these factors. Therefore, an analysis of habitatuse patterns may identify other factors that function as determinants of habitat use, By combining data on habitat use by wading birds at a series of locations in Florida Bay in conjunction with an analysis of habitat topography and hydrography, I tested two null hypotheses. First, in the absence of restrictions imposed by a tidal cycle, foraging habitat use would be independent of time. And second, in the absence of a strong annual climatic cycle (temperature), habitat use by wading birds would be constant throughout the year.

Incubation Behavior of Emperor Geese Compared with Other Geese: Interactions of Predation, Body Size, and Energetics

Abstract: --The incubation constancy of 11 female Emperor Geese (Chen canagica) was monitored electronically and behavior of both sexes was observed during incubation recesses in 1983 and 1984 at Kokechik Bay, Alaska. Average nest attentiveness of female Emperor Geese was 99.5% during 4,800 h of monitored incubation time. Recesses averaged (_+SE) 13.3 _+ 0.8 min, and modal recess length was 8 min (n = 107). Recess frequency was 0.54/ day. This high degree of nest attentiveness exceeded that reported for any goose species. Nest attentiveness did not vary significantly through the incubation period, but increased in the last 3 days, probably in response to embryo noises and pipping. Most recesses (45%) occurred between 1200 and 1800, the warmest portion of the day. There were no significant differences in recess length at different times of day, however, and recess duration and frequency were not related to differences in daily temperature or wind speed. Females fed for only 14% of the time during their infrequent and brief recesses. Most time (43%) during recesses was spent preening and bathing. Males were alert for 49% of the time females were on recess but were present during only 56% of recesses, reflecting their relative lack of attendance during incubation. Behavior of females during recesses when males were absent did not differ significantly from when males were present. The high incubation constancy, loss of body mass during incubation (20.7%), and relatively large average clutch size (5.2) indicate that Emperor Geese arrive on nesting grounds with an extremely high level of endogenous reserves relative to other geese. Clutch size and incubation behavior also represent trade-offs in energy investment related to body size, egg size, food availability, and feeding needs during incubation. Generally, larger species or subspecies of geese depend more on endogenous reserves than do smaller forms. We believe, however, that this relationship is not satisfactorily explained just by energetic constraints related to body size because Emperor Geese were more attentive to incubation than even larger goose species. Emperor Geese usually can defend their nests from arctic foxes (Alopex lagopus) but, when on incubation recesses, are apparently less efficient in defense against avian predators than sympatric-nesting smaller geese. These smaller species are more vulnerable to foxes but more agile and effective against avian predators. The incubation constancy of geese results from an interaction of predation pressures related to body size and defense capabilities. Received 28 July 1986, accepted 18 May 1987. ONLY female geese incubate, relying heavily on body reserves for the energy and materials needed for clutch formation and incubation (Ankney and Macinnes 1978; Raveling 1979a, b). The level of reserves that remain after egg laying determines how a female goose will allot time between nest attentivehess and incubation breaks for feeding. Geese that are least attentive to nests lose the most eggs to predators (Harvey 1971, Inglis 1977, Raveling and Lumsden 1977). Males play an important role in the detection and deterrence of predators (Ankney 1977, Raveling 1979a, Fox and Madsen 1981, Raveling 1981, Aldrich 1983). Therefore, the incubation behavior of a species should be strongly affected 707 by variables such as food availability and quality, body size, predation pressure, and behavior

Critical evaluation of DNA hybridization studies in avian systematics

Abstract: -It is frequently claimed that equal rates of DNA evolution are observed in birds, but specific tests necessary to demonstrate this are rarely performed. I demonstrated statistically significant differences in rates of DNA evolution for a few passerine birds that vitiate the role of DNA hybridization as the direct indicator of kinship. The differences in evolutionary rates observed may be substantial enough to introduce ambiguity into the clustering of taxa. Researchers frequently fail to perform the specific experiments needed to distinguish between real differences in relative rates of DNA evolution vs. differences that can be attributed to experimental error. They also fail to draw attention to and account for either erroneous or problematical data for some birds, or fail to perform the experiments necessary to determine the cause of unexpectedly problematical results. The DNA molecular clock is shown to be calibrated using speculative and questionable data. It involves diverse organisms that cannot be shown to evolve at the same rate, and that probably did not. Yet, DNA hybridization is a valuable tool that probably cannot lead one to make major systematic errors providing the data are not incorrect because of technical or computational errors and are taken from a sufficient diversity of relevant taxa. Received 29 November 1985, accepted 8

Ecology and physiology of fasting in King Penguin chicks

Abstract: -Captive King Penguin (Aptenodytes patagonica) chicks can fast for 5 months during the subantarctic winter with a 70% decrease in body mass. To investigate the adaptive value of this remarkable resistance to starvation, we compared captive chicks with freeranging chicks in their colony at Possession Island, Crozet Archipelago. The chicks in the colony, from mid-April to beginning of September (i.e. all winter) were fed only every 39 days by their parents; some were not fed at all. In spring (October-December) the surviving chicks were fed every 6 days, and their growth was completed. Overall chick mortality in the colony during the winter and subsequent spring was about 50%. Mortality was highest in October, 6 months after the beginning of the winter, and may be attributed mainly to starvation. The decrease in body mass in the free-ranging chicks was remarkably similar to that for captive birds. In both groups, three periods were characterized according to the observed changes in the daily decrease in body mass per unit body mass (dm/ mdt): dm / mdt dropped during the first period (I) of 5-6 days, was minimum and steady during period II, which lasted about 4 months, and increased in period III. Blood analysis of the captive chicks indicated the three periods correspond to modifications in protein breakdown. An initial decrease in uricacidemia indicates period I is a short period of transition, marked by a decrease in protein breakdown. In period II a minimum and constant uricacidemia, in parallel with a progressive increase in ketonemia, indicates efficient protein sparing while most of the energy is derived from lipids. Period III is critical because, from a rise in uricacidemia concomitant with a decreasing ketonemia, proteins are no longer spared. The extreme resistance of King Penguin chicks to starvation in winter may be explained partly by the ability to spare proteins for several months (period II). It occurs at a growth stage when the parents' feeding visits are rare. Other laboratory and field investigations of birds suggest that the means by which a wide variety of domestic and wild species adapt to fasting also may be interpreted in terms of three periods corresponding to changes in protein breakdown. Received 6 June 1986, accepted 30 October 1986. RECENT physiological data show that King Penguin (Aptenodytes patagonica) chicks resist starvation in winter remarkably well. At 3-4 months of age they may tolerate a fast of 4-6 months and a 70% decrease in body mass (Cherel and Le Maho 1985). King Penguin chicks are fed infrequently during winter and have a very high mortality due to starvation (Stonehouse 1960). No quantitative information seems to be available on the duration of the fast or the rate of decrease in body mass. The adaptive significance of the extreme resistance to starvation observed in experimental chicks therefore remains poorly understood. The fledging period of King Penguin chicks 3Present address: National Museum of New Zealand, Private Bag, Wellington, New Zealand. lasts about 11 months. This prolonged down stage may be divided into three parts (Stonehouse 1960, Barrat 1976). First, from hatching in mid-January, the chicks are fed regularly; they grow rapidly and reach a body mass of 10-12 kg in 3-4 months. Then, from May to August during the austral winter, the chicks are left alone for long intervals and not fed. Their body mass falls to about two-thirds or one-half of the autumn maximum. When the parents resume feeding (October-December), growth is completed, and the chicks molt before going to sea. A wide variety of birds fast and exhibit a decrease in body mass during certain stages of their annual life cycle. Birds fast when food is scarce (Trautman et al. 1939), but also when it is plentiful if they are engaged in other important activities that compete with feeding, 254 The Auk 104: 254-262. April 1987 This content downloaded from 157.55.39.135 on Sun, 03 Jul 2016 04:33:52 UTC All use subject to http://about.jstor.org/terms April 1987] Fasting in King Penguin Chicks 255 such as incubation, molting, and migration (Mrosovsky and Sherry 1980). Although there has been recent interest in the energetics of birds fasting during breeding (Croxall 1982, Le Maho 1984), to our knowledge there are no comparisons of physiological data on fasting in captive birds with similar data on free-ranging animals. We report here the changes in body mass, rates of feeding, and mortality in free-ranging King Penguin chicks during winter and spring, i.e. during seasons of food shortage and growth, respectively. We measured also fast duration and changes in body mass and plasma concentration of uric acid and f-hydroxybutyrate (fOHB) in captive chicks. Uric acid is the major nitrogen excretory product in birds (Poulson and MacNabb 1970) and is an index of protein breakdown in penguins (Robin et al. 1983). On the other hand, an increase in plasma concentration of f-OHB, the main ketone body in birds, characterizes the part of a fast during which most energy is derived from lipids (Le Maho et al. 1981). MATERIALS AND METHODS Field and experimental studies were performed at Possession Island, Crozet Archipelago (46?25'S, 51?45'E), between April and December, during the subantarctic winter and following spring. Two groups of King Penguin chicks were used: free-ranging birds in the breeding colonies of Baie du Marin and chicks caught in these colonies and kept in the nearby sta-

Activity Budgets and Foraging Ranges of Breeding Common Murres

Abstract: We used electronic activity recorders to measure flight time, dive time, and time on the water of breeding Common Murres (Uria aalge). During both incubation and chick rearing, about 90% of birds' time away from the colony was spent on the water or diving and 10% was spent flying. The proportion of flight time did not vary with trip duration. During chick rearing, 13.6% of time away from the colony was spent diving, and the proportion of time spent diving tended to decrease with trip duration. Potential foraging ranges calculated from flight times during individual foraging trips showed a concave frequency distribution, and median potential ranges were 37.8 km for incubating birds and 5.4 km for chick-rearing birds. The use of electronic recorders to measure time budgets has broad applications for seabird energetics and foraging ecology and for the assessment of prey availability and abundance. Received 21 April 1986, accepted 13 October 1986.

Feeding and Nesting Ecology of Sympatric South Polar and Brown Skuas

Abstract: --In the 1979-1980 and 1980-1981 austral summers, I examined nesting and feeding ecology of South Polar (Catharacta maccormicki) and Brown (C. lonnbergi) skuas near Palmer Station, Antarctica. As earlier studies had suggested, South Polar Skuas fed mostly at sea on fish, and Brown Skuas fed mostly on penguin eggs and chicks. These dietary differences correlated with differences in the skuas' time budgets, activity patterns, territory types, breeding chronologies, nest densities, clutch sizes, and fledging success. With combined data from this and other studies at Palmer, I calculated average productivity for both species over 7 breeding seasons. Brown Skuas fledged higher and more consistent numbers of young per pair, probably because of their more accessible and reliable food source. Received 13 March 1985, accepted 18 January 1987. SKIdAS of the Southern Hemisphere are well known for their opportunistic feeding habits. South Polar Skuas (Catharacta tnaccorrnicki) and Brown Skuas (C. Ionnbergi) • have been recorded as predators, scavengers, and kleptoparasites on a wide variety of organisms (e.g. Stonehouse 1956; Young 1963a, 1978; Burton 1968; Johnston 1973; Moors 1980; Sinclair 1980; Maxson and Bernstein 1982; Osborne 1985; Green 1986). Despite their opportunism, most skuas depend primarily on a few prey types. Where they nest allopatrically on the coasts of the Antarctic Continent, South Polar Skuas generally fish at sea, prey on penguin eggs and chicks, or both (Eklund 1961, Young 1963a, Le Morvan et al. 1967). On subantarctic islands, allopatric Brown Skuas feed primarily on penguin eggs and chicks or on adults of small Procellariiformes (Stonehouse 1956, Young 1978, Jones 1980, Moors 1980, Sinclair 1980, Fraser 1984, Osborne 1985). Brown and South Polar skuas nest sympatrically in a few areas, mostly along the Antarctic Peninsula between 61 o and 65oS. At these sites there appears to be a sharp partitioning of food resources; Brown Skuas monopolize the terrestrial food source of penguin eggs and chicks, and South Polar Skuas forage almost exclusively at sea (Parmelee et al. 1978, Trivelpiece et al. 1980, Hemmings 1984). One might expect to find other differences in • Pending resolution of their taxonomic status, I refer to these as full species. For discussions of skua systematics and nomenclature, see Pietz (1984, 1985). Brown and South Polar skua ecology that correlate with these differences in diet. A few such correlates already have been documented. Nellson (1983), near Palmer Station on Anvers Island (64o46'S, 64o03'W), and Trivelpiece and Volkman (1982), at Point Thomas on King George Island (62o10'S, 58o30'W), noted parallels between breeding chronology and food habits. Nellson also noted differences in average duration of foraging trips, and both Trivelpiece et al. (1980) and Nellson observed differences in fledgling success. My purpose was to examine skua ecology and behavior for correlates of the observed dietary differences. Possible correlates such as time budgets, diurnal activity patterns, and variation in egg and clutch size received little or no attention in earlier studies. Aspects of skua ecology studied previously merit further attention because skuas are long-lived birds (probably a 30-40-yr life span; Ainley 1981) and experience tremendous variability in feeding conditions within (Parmelee et al. 1978) and between (e.g. Trillreich 1978, Trivelpiece et al. 1980) nesting grounds. STUDY AREA AND METHODS This study was conducted during the 1979-1980 and 1980-1981 austral summers on several small islands and peninsulas within 5 km of Palmer Station. The ice-free areas around Palmer provide nesting sites for nearly a dozen bird species (Parmelee et al. 1977), including over 200 pairs of South Polar Skuas and up to 12 pairs of Brown Skuas. Each year there is also at least one mixed-species pair, usually consisting of a 617 The Auk 104: 617-627. October 1987 618 P^MEL^ J. Pmrz [Auk, Vol. 104 South Polar Skua male and Brown Skua female. These mixed pairs produce viable hybrid offspring, capable of producing viable F2 offspring (Parmelee and Rimmet pets. comm.). Most skuas involved in this study were color-banded to allow individual recognition at a distance. Birds were captured with long-handled hand nets at the nest sites, or with rocket nets at bait sites. Most had been banded in previous years and thus had known breeding histories. Sexes were determined from observations of their copulatory positions, their roles in courtship feedings, or both. Diet.--Neilson studied skua feeding habits at Palmer in the mid-1970's; he noted (Nellson 1983) that many Brown Skua pairs defended Ad•lie Penguin (Pygoscelis adeliae) colonies near their nest sites as feeding territories. Like Neilson, I gathered data on skua diets by recording foods regurgitated when adults fed chicks or mates and when adults or chicks were captured. Additional information came from direct observations of adult foraging activity. Time budgets.--During observation periods at several skua nest sites, the behavior of each pair member was noted every 30 s using a metronome (Wiens et al. 1970). From these records hourly and daily time budgets were constructed for each individual and pair. A total of 4,058 bird-hours of observations was made in the two seasons. Between 8 December 1979 and 22 January 1980, a field assistant and I documented the behavior of 4 South Polar Skua pairs, 2 Brown Skua pairs, and 1 mixed-species pair using 24-h sample periods. We obtained 50 bird-days of observations for South Polar Skuas, 14 for Brown Skuas, and 8 for the mixed pair. Between 27 January and 9 March 1980, when increasing darkness prevented 24-h observations, we watched each of the 7 pairs for 6 dawn-todusk periods. From 7 January to 6 March 1981 I made additional observations, using sample periods of 314 h. Eight South Polar Skua pairs, 2 Brown Skua pairs, and 1 mixed pair were sampled in the second season. The mixed pair, 1 Brown pair, and 4 South Polar pairs were observed in both years. Some related behaviors were combined before time budget analysis. Grouped behaviors included resting (sitting, incubating, and brooding), foraging (procuring, transporting, and eating prey, and out of view off the nest territory), pairing (courtship and courtship feeding, copulation and attempted copulation), agonistic displays (long call, alarm call, bent neck, and wing raising), and agonistic encounters (running or flying displacement, swooping, aerial chasing, and fighting). Skuas were assumed to be resting during hours of darkness. Assessment of foraging behavior presented special problems related to differences in observability of terrestrial and marine feeding. Total foraging time included periods when birds were off their territories and out of view as well as when they were feeding visibly (see Pietz 1986). Breeding biology.--I divided the breeding season into (1) pre-egg laying, (2) incubation (after the first egg was laid), (3) brooding (after the first chick hatched), (4) postbrooding (after the first chick was no longer brooded regularly), and (5) fledging (when the first chick flew well enough to avoid capture). A sixth category (failed-nest) contained observations on pairs following loss of eggs or chicks. Of the 4 South Polar Skua pairs observed in 19791980, 1 courted and defended a territory but failed to produce eggs. For comparison with the 3 breeding pairs, this pair's eggless season was divided into sections based on the average timing of incubation and brooding of the breeders. In each season, breeding chronologies, egg sizes, chick growth rates, and reproductive success were documented for over 20 South Polar Skua pairs and for all Brown Skua and mixed-species pairs in the study area. Egg volumes were calculated from measurements of length and breadth, using the formula V = (0.00048)LB 2(Furness 1983). Chicks were weighed and their tarsi and seventh and tenth primaries measured every 2-4 days. Nest counts, fledgling counts, and notes on breeding chronology were recorded for the Ad•lie Penguin colonies. Approximately 14,000 Ad•lie pairs nested on islands in the study area.

Effect of experimentally altered brood size on frequency and timing of second clutches in the great tit

Abstract: Brood size in the Great Tit (Parus major) was manipulated (increased, decreased, or unchanged) when nestlings were 5 days old. Both the frequency of second clutches and the interbrood interval were affected. The number of nestlings and hatching date, but not nestling and female mass, differed between first broods followed and not followed by second clutches. Hatching date and the number of nestlings in the first brood explained most of the variation in interbrood interval, whereas female mass did not contribute. Feeding first-brood nestlings and fledglings is an energy-demanding process, and the female may have to allocate resources to brood-feeding at the expense of reproductive de- velopment. Furthermore, a larger brood requires a longer period of feeding than a smaller brood. These circumstances probably explain why the size of the first brood affects the timing of the second clutch. Female condition and food depletion of the territory do not seem to be important. Because late second clutches have a lower probability of fledgling survival than do earlier ones-and consequently are of lower value from the female's standpoint-a large first clutch may delay laying to the point that a second clutch is not worthwhile. We conclude that a female's decision whether to lay a second clutch is a strategic one based on the value of the second clutch; a female that "decides" to lay a second clutch starts as quickly as possible. (Less)

Sugar-tasting ability and fruit selection in tropical fruit-eating birds

Abstract: The sugar-tasting abilities of four species of tanagers and two species of man- akins were tested. Three tanager species were able to detect differences in diets containing 8%, 10%, and 12% sugar. In pairwise choice trials, they preferred the diet highest in sugar. Neither species of manakin discriminated among the three diets. This apparent difference in tasting abilities of tanagers and manakins may be a result of their fruit-handling tech- niques. Tanagers crush fruits in their bills, thereby releasing juices onto their tongues. Man- akins swallow fruits whole; their tongues rarely encounter fruit juice. Hence, manakins' fruit- handling technique is poorly suited for sensing the taste cues in fruit juices. Variation in fruit sugar concentration is common within and among plant species and is great enough to be detected by birds. Birds probably have selected for sweeter fruits. Received 17 April 1986, accepted 22 September 1986.

Spacing of adult and subadult male Common Capercaillie during the breeding season.

Abstract: -The spacing behavior of 58 male Common Capercaillie (Tetrao urogallus) was studied at Varaldskogen in southeast Norway during 1979-1985. Birds captured at leks were equipped with radio-transmitters, and their movements were monitored throughout the year. During spring, males 4 yr old and older occupied exclusive day territories of 10.2-66.0 ha that extended radially from a center at the lek. Adult cocks used the same lek and the same territory during successive years. Among marked birds, the youngest bred at 4 yr. No difference was found in territory size between breeding and nonbreeding adult males. Territories of 3-yr-olds (60.8 ? 10.4 ha) were larger than those of older males (26.3 ? 5.0 ha) and were located farther from the lek. All territories were within a 1.2-km radius of the lek center and were maintained from early April to the end of May. Yearlings and 2-yr-old males were nonterritorial. They moved irregularly among different, neighboring leks, settling near one lek at the end of their second spring season. When associated with one lek, their home ranges were 3-6 times larger than and overlapped peripherally the territories of resident adults. Established subadult and adult males did not change territories when vacancies were created by deaths of older birds, and successful matings were not dependent on occupying a particular territory. Received 16 December 1985, accepted 7 March 1987. THE Common Capercaillie (Tetrao urogallus) is the largest and most sexually dimorphic tetraonid species. Males are polygynous and interact with females only when they visit the lek for a few days to mate in early spring. Based on the spatial arrangements of males at the lek, where individuals are reported to occupy large contiguous or noncontiguous territorial centers of 0.1-0.8 ha (Lumsden 1961, Muller 1979, Hjorth 1985), the mating system is not considered by most authors to be true lekking. Wittenberger (1978, 1981) classified the capercaillie with the forest-dwelling grouse of North America that have dispersed territories. Oring (1982) considered the capercaillie more leklike and classified it as the only tetraonid in an intermediate group, more clustered than the ones above, but less aggregated than his third category that included the prairie grouse of North America and the Eurasian Black-Grouse (Tetrao tetrix). De Vos (1979) also considered the capercaillie in an intermediate type, whereas Wiley (1974) considered it a true lek-forming species. Much of the confusion and difficulty regarding classification of mating systems stems from incomplete knowledge of the spatial and social relationships of the birds when they are not on the display grounds. On the basis of long-term behavioral studies of capercaillie in Sweden, Hjorth (1982) considered how males were spaced around the lek during the day. He noticed that each male departed from the lek in the same direction from which it had arrived and that two males never arrived from, or departed in, the same direction. From this, he suggested that males probably live solitarily in separate home ranges and that these were spaced regularly around the lek. Although no supporting data were presented, Hjorth (1982, 1985) implied further that the home ranges extend up to 2 km from the lek and were used by the males yearround. Our preliminary observations using radiotelemetry (Larsen et al. 1982, Wegge et al. 1982) supported Hjorth's general hypothesis, but suggested that it applied only to adult birds during the breeding season. In other promiscuous North American tetraonids, adult males claim territories during the breeding season, while yearlings are nonterritorial and move about in search of unoccupied areas on which to settle (Bendell and Elliott 1966, Gullion 1967, Ellison 1973, Ballard and Robel 1974, Rippin and Boag 1974, Boag 1976, Herzog and Boag 1978, Zwickel 1980). In the Ruffed (Bonasa umbellus) and the Blue (Dendragapus obscurus) grouse, some adults also may be 481 The Auk 104: 481-490. July 1987 This content downloaded from 207.46.13.166 on Thu, 07 Jul 2016 05:25:25 UTC All use subject to http://about.jstor.org/terms 482 WEGGE AND LARSEN [Auk, Vol. 104 nonterritorial (Lewis and Zwickel 1980, Gullion 1981, Lewis 1984). During spring, nonterritorial yearlings of Spruce (D. canadensis) and Blue grouse and most lek-forming species move considerably longer distances than resident adults, and lek species make temporary visits to neighboring leks (Koivisto 1965, Ballard and Robel 1974, Rippin and Boag 1974, de Vos 1983). We report on the spring spacing pattern of Common Capercaillie males of different age and social status based on radio-tracking 58 individuals during 7 yr in southeast Norway. We discuss the mating system of this species along the continuum from clumped (leks) to dispersed polygyny and report on recruitment and age-related territoriality among males. STUDY AREA AND METHODS The study was conducted during 1979-1985 at Varaldskogen Field Station (60?10'N, 12?30'E) in Hedmark Co. in southeast Norway. Varaldskogen is in the middle boreal zone (Abrahamsen et al. 1977); coniferous forests of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) dominate the vegetative complex. Birch (Betula verrocosa) is the most common deciduous tree, and blueberry (Vaccinium myrtillus) and heather (Calluna vulgaris) dominate the ground layer on undisturbed sites. Intensive logging and forest management have been practiced here for the last 30-40 yr. At the time of our investigation, about 36% of the study area was composed of clear-cuts and spruce and pine plantations up to 8 m in height; 43% of mature, largely undisturbed forest; and 10% of open, treeless peat bogs. The fauna is typical of the middle boreal zone. Because of habitat deterioration and low recruitment, the population of T. urogallus was declining, averaging approximately 0.8 males/km2 in spring in the 40km2 study area (Wegge 1983, 1984, unpubl. data). We captured males at leks and attached radio transmitters to their backs (Brander 1968) with a nylon harness enclosed in silicon rubber to prevent feather and skin abrasion. Transmitters weighed about 100 g (2-3% of body mass), with a transmitting distance of 2-3 km and a battery life of about 700 days. The instrumentation seemed to have no adverse effects because successful matings were observed subsequently among radio-marked individuals of both sexes, and survival rates were high (Wegge 1984). Males were aged according to beak measurements (Moss et al. 1979), using the following age-class intervals based on recaptured birds of known age in the study area. Males with beaks smaller than 23 mm were classified as yearlings (10-11 months old), males with beak depths of 23-25.5 mm were classified as 2-yr-olds (22-23 months), and males with beaks deeper than 25.5 mm were classified as adults (3-yr-old and older birds). Because a number of young males were studied in successive years, 9 known 3-yr-olds could be distinguished from others among the adult age group. Each year during the breeding season, two or more persons were usually present every night on each of 3-6 leks to capture and observe display and breeding activity. We classified radio-equipped males as breeders or nonbreeders on the basis of observed mating performance. Any male that was observed to mate was defined as a breeding male, whether he mated many or few hens. During most years and at most leks, one male dominated the mating. We captured and radio-marked 58 males at 6 leks during the spring seasons of 1979-1985. Several were recaptured during the summer molt and observed in successive seasons. Most telemetry work was carried out at 3 leks; one lek served as the main study population. Active leks (n = 23) in a larger overall study area were spaced regularly, with a mean minimum distance of approximately 2 km (Wegge and Rolstad 1986). The locations of most radio-marked males were determined nearly every morning or late evening in the lek area. During the day their movements and locations were determined 3-7 times/week, except during the seasons of 1982-1984 when some males at two leks were tracked more intensively. Daytime locations, when birds were not on the display ground, were taken between 1000 and 2000, distributed evenly throughout the day. We observed males from 16 April until they ceased to attend leks for morning display. This varied among age groups: most adults attended the leks throughout May, whereas yearlings and most 2-yr-olds usually abandoned the leks 7-10 days earlier. A total of 1,051 positions was recorded when males visited the leks, and 1,238 positions were recorded during daytime when they were away from the lek. Morning locations were used to study the movement of males among and on leks, whereas daytime locations were used to estimate sizes of home ranges and other measures of spacing. We determined the position of each bird by the intersecting compass bearings from two or three elevated vantage points. Approximately 60% of all locations were triangulated to an area of 0.3 ha or less. Locations derived from two compass bearings at close distance were of similar precision. When tracking at longer distances (>500 m), such positions (19%) were less accurate. A disproportionately larger number of the lower-precision fixes were recorded on subadult males. We omitted these when making home-range

Response of adult Leach's storm-petrels to increased food demand at the nest

Abstract: -In a colony of Leach's Storm-Petrels (Oceanodroma leucorhoa) on Kent Island, New Brunswick, i chicks were rotated on a daily basis through n nests to produce i/n chickequivalents of food requirement, increasing by small increments from 1 (i = 6, n = 6) to 2 (i = 2, n = 1), between ages 10 and 50 days. Food delivered each night (SUM) was estimated by 24-h increments in chick mass. In nonexperimental nests SUM varied significantly among pairs, and chick mass varied in direct relation to SUM. Adults tending experimental nests did not respond to increased food demand, and chick mass decreased with increasing chickequivalent per nest. After rotations were terminated, the mass of most chicks increased quickly to normal levels. These results suggest that the average amount of food delivered daily by each parent is determined independently of food demand and that chicks attain a mass that balances a fixed food intake against food requirement, which varies in direct relation to mass. Received 29 September 1986, accepted 17 June 1987. PELAGIC seabirds typically rear a single, slowly growing chick. This pattern of reproductive performance characterizes species in several taxonomic orders and in a wide variety of marine environments from the tropics to high latitudes. Two types of explanations have been offered for this low productivity. Lack (1968), Nelson (1977), and others have argued that breeding productivity is limited by the availability of food in the environment or by the ability of adults to transport food between the feeding and nesting sites. Alternatively, some authors have suggested that pelagic seabirds reduce breeding productivity below the level they are capable of supporting either to reduce the stress of reproduction and thereby prolong life (Goodman 1974, Dunn 1979) or to prevent overpopulation (Wynne-Edwards 1962). These two classes of hypotheses can be distinguished by the ability of adults to increase their rate of food delivery to the nest in response to increased demand. Accordingly, if feeding rate were maximized at a level imposed by resource availability or ability to transport food, then feeding rate could not be increased. If, however, feeding rate were optimized at a lower level, parents would be able to respond to increased food demand at the nest. Several investigators have attempted to increase the food demand of the brood by adding a second chick. Such experiments have met with mixed success, generally failing to elicit marked responses in Procellariiformes (Rice and Kenyon 1962; Huntington 1963; Harris 1966, 1969) but leading to increased feeding rate and successful rearing of twins in Swallow-tailed Gulls (Creagrusfurcatus, Charadriiformes; Harris 1970) and gannets (Sula spp., Pelecaniformes; Nelson 1964, Jarvis 1974). Cross fostering the chicks of a larger species into the nests of a smaller, related species also has stimulated increased food provisioning by parents in Gray-backed Terns (Sterna lunata; Shea and Ricklefs 1985). The failure of petrels (Procellariiformes) to respond to the presence of twins is difficult to interpret with respect to the contrasting hypotheses of maximized vs. optimized feeding rate. Although the results are consistent with resource limitation, twinned chicks may interact so as to interfere with proper communication with adults. Recent studies have demonstrated the influence of chick-chick interactions within broods on feeding rates (Henderson 1975; Bengtsson and Ryden 1981, 1983; Stamps et al. 1985). Furthermore, storm-petrel parents may not be suitably responsive to the novel family situation created by the twinning experiment. Finally, the feeding rates of parents may be fixed to match average food demand, and not to respond to variation in the nutritional level of the chick. Petrel chicks vocalize when a parent is at the nest, and actively solicit food, but it is not known whether solicitation varies with respect to level of nutrition. The experiment reported here was designed to chronically increase the food demand of chick rearing for storm-petrels without there being more than one chick in the nest at any time. By 750 The Auk 104: 750-756. October 1987 This content downloaded from 157.55.39.132 on Thu, 15 Sep 2016 05:05:30 UTC All use subject to http://about.jstor.org/terms October 1987] Parental Feeding in Leach's Storm-Petrel 751 rotating a number of chicks among a smaller number of nests on a daily basis, I created a graded food demand, ranging from 1 to 2 chickequivalents. This experimental design circumvented some of the potential problems of twinning experiments but raised others. A positive parental response to increased food demand could mean that foraging effort is normally regulated below the maximum possible. But a failure to respond would be consistent with several alternative explanations. Among these are: (1) parents cannot deliver more food, (2) chicks do not increase solicitation when deprived, and (3) the presence of different chicks in the nest from night to night so confuses the parents that they cannot respond appropriately.

Field Metabolism and Food Consumption of Savannah Sparrows during the Breeding Season

Abstract: -I applied the doubly labeled water (DLW) technique to measure rates of water flux and energy expenditure of Savannah Sparrows (Passerculus sandwichensis) during two breeding seasons on Kent Island, New Brunswick, Canada. Simultaneous to DLW measurements, I constructed time-activity budgets for territorial males, monitored nest attentiveness for incubating females, and quantified frequency of nest visitation for parents feeding young. To ascertain the relationship between brood size and adult energy expenditure, I measured the energy expenditure of adults feeding 2, 4, and 6 nestlings. There was little difference in field metabolic rates (FMR) between territorial males [161.0 ? 21.7 (SD) ml CO2/h] and males that fed 4 nestlings (157.6 ? 19.7 ml CO2/h). Incubating females expired CO2 at rates lower than males during the same time period (134.4 ? 7.9 vs. 161.0 ? 21.7 ml CO2/h) but similar to rates for females feeding 4 young, the normal brood size (134.4 ? 7.9 ml CO2/h for incubating females vs. 136.5 ? 26.9 ml CO2/h for females feeding young). Incubating females expended energy at a lower rate than females making 8 or more trips to the nest per hour, the average feeding rate for females late in the nestling period. For males and females together, water influx and efflux rates averaged 17.1 ? 3.2 and 17.2 ? 3.0 ml H2O/day, suggesting that birds balanced water intake against water losses. Mean daily solar radiation (MDSR; W/m2) also influenced FMR during the nestling period. The equation ml C02/h = 172.6 0.07 (MDSR) described the relationship. When brood sizes were manipulated, parents responded by altering their frequency of nest visitation; as frequency increased, so did the FMR of females but not of males. The equation ml CO2/h = 98.4 + 5.3 (mean visits/h) described the relationship. Construction of a food budget indicated that, on average, territorial males consumed 21.1 g fresh arthropods per day, while incubating females ingested 17.5 g/day or 210.0 g during the 12-day incubation period. Through the 8-day nestling period, males augmented their foraging by 75%, females by 87%, to feed a brood of 4. Received 20 March 1986, accepted 6

Determinants of great blue heron colony distribution in coastal Maine

Abstract: -The distribution of nesting Great Blue Herons (Ardea herodias) in coastal Maine was studied by examining the relationship between colony size and availability of food supplies near colonies, the selection of nesting habitat, and the spacing of colonies. Nineteen colonies (size range 4-252 nests) were located, all on marine islands. The number of nests in a colony was correlated positively (r = 0.82) with the area of tidal and inland wetlands within a 20-km radius of a colony. Nest and colony characteristics were highly variable, and suitable nesting habitat did not seem to limit colony size or distribution. The degree of forestation, presence of hardwoods, and distance of an island from towns and other islands with colonies were apparently important factors in selection of nesting islands. Colonies were uniformly distributed along the coast at intervals of about 16 km. We present a model for the observed dispersion of heron nests based on the conclusion that food competition between members of the same colony probably limits the size of colonies, whereas food competition between members of adjacent colonies may determine colony distribution. Received 7 February 1986, accepted 16 June 1986. THE value of nesting in colonies has been examined by a number of workers (Lack 1968, Ward and Zahavi 1973, Hoogland and Sherman 1976, Krebs 1978, Burger 1981, Gotmark and Andersson 1984), but less is understood of what determines where a group of birds will form a colony or how large that group will be. Determinants of colony location tend to complement factors that contribute to colonial nesting behavior. Two examples are increased protection from predators through the selection of inaccessible nesting grounds (e.g. Cullen 1957, Burger and Lesser 1978, Nelson 1978) and enhanced utilization of resources by nesting close to food resources (Ward and Zahavi 1973; Kushlan 1976a, 1978). Determinants of the number of individuals in a colony are less well understood. Among other factors, competition for sites may limit colony size, i.e. the number of individuals breeding in a colony, in some groups, e.g. some sulids (Nelson 1966), while food availability may limit colony size in ardeids (Werschkul et al. 1977, McCrimmon 1978, Beaver et al. 1980), phalacrocoracids, alcids, sulids, and larids (Fur3Present address: Division of Biological Sciences, 105 Tucker Hall, University of Missouri-Columbia, Columbia, Missouri 65211 USA. ness and Birkhead 1984). Measuring a relationship between food availability and colony size is difficult because food resources used by colonial birds are typically patchy and temporary and are spread over vast areas around colonies. Our purpose was to examine possible determinants of the distribution of nesting Great Blue Herons (Ardea herodias) in the coastal region of Maine. Nesting Great Blue Herons are large and conspicuous, and thus colony locations and sizes can be readily determined over a large area. Great Blue Herons also feed primarily in local, relatively permanent, wetland habitats. Relationships between colony size and an index of food resource availability, i.e. wetland availability, can be determined easily. We describe the pattern of nest dispersion for Great Blue Herons in the region. We then examine the relationship between the number of herons breeding in a colony and availability of foraging habitat; the selection of nesting habitat by herons by comparing the characteristics of nesting areas with those of similar, but unused, areas; and the spacing of colonies.

A New Paradigm for the Analysis and Interpretation of Growth Data: The Shape of Things to Come

Abstract: The process of growth is basic to all organisms, and studies of growth have long been a subject of concern to ornithologists. At a workshop held at the recent meeting of the American Ornithologists' Union (1821 August 1986), a series of presentations and subsequent discussions laid the foundation for what we feel to be a new paradigm for studying growth. The strengths of this new paradigm lie in its potential for more detailed quantitative comparisons of growth in general and intraspecific comparisons in particular. It is our purpose to summarize the major aspects of this paradigm and to provide information on its development. The paradigm was derived mainly from studies of birds, but should have broad applicability to studies of a variety of organisms. Growth was first studied qualitatively by describing developmental stages in chronological series. This was followed by quantitative formulations that considered growth as the net result of simultaneous anabolic and catabolic processes. Many of these early concepts (e.g. Huxley 1932, von Bertalanffy 1957) still influence current thinking. A third stage was introduced by Ricklefs (1967), based on a graphical method of fitting data to S-shaped or sigmoid growth models. This methodology, applied to interspecific comparisons, has contributed significantly to our understanding of the meaning of the patterns of variation in avian growth-particularly from an evolutionary point of view (Ricklefs 1983). The new paradigm is also based on the fitting of data to sigmoid models but is directed more toward questions that involve intraspecific as well as interspecific comparisons. The Richards sigmoid growth function (Richards 1959) and its expression in terms of parameters with specific biological meaning (Bradley et al. 1984, Brisbin et al. 1986b) have been of basic importance to the new growth paradigm. These approaches now allow independent quantitative assessments of three biologically meaningful aspects of growth: (1) size, the upper or asymptotic limit; (2) rate, a measure of the time required for specified growth increments to take place; and (3) shape, a quantitative measure describing

Factors affecting variation in the egg and duckling components of Wood Ducks

Abstract: -We collected 3 eggs from each of 35 female Wood Ducks (Aix sponsa). Freshegg mass averaged 44.2 g and consisted of 53.1% albumen, 36.4% yolk, and 9.6% shell. Albumen and yolk contained 86.2% and 44.9% water, respectively. Lipids comprised 65.1% of the dry yolk. All egg components except dry albumen increased in direct proportion to fresh-egg mass. Variation among females explained 52-80% of the total variation in mass and composition of eggs. Body mass of hens during early incubation was correlated with estimates of pre-egg-laying lipid reserves (rs = 0.66); therefore, body mass was a good measure of female quality. Body mass of females was independent of age and structural size, and was positively related to mean egg mass, egg composition, energy content of eggs (kJ/g), and clutch mass, but not to clutch size or time of nesting. Female body mass explained more variation in albumen components than in yolk or shell components. These results support Drobney's (1980) hypothesis that prebreeding condition of female Wood Ducks is important because it allows hens to accumulate exogenous protein for egg synthesis. The data do not support predictions based on optimal egg size theory. The body mass of ducklings averaged 23.7 g (n = 43); there were no intersexual differences in mass or composition. Ducklings contained 65.9% water and 32.5% lipids (dry mass). Components of ducklings increased in direct proportion to fresh-egg mass, but egg mass was a poor predictor of duckling lipid content. Received 8 October 1986, accepted 2 February 1987. INTEREST in how females partition energy for reproduction has been stimulated partly by the positive relationship between egg size and fitness parameters of newly hatched birds, i.e. size (Schifferli 1973, Moss et al. 1981), survival (Parsons 1970, Lundberg and Vaisanen 1979, Ankney 1980), and growth rate (O'Connor 1975, Williams 1980). In general, egg size varies within and between populations, with most variation (50-98%) attributable to differences among females (Ojanen et al. 1981, Grant 1982, Ricklefs 1984). There is a large heritable component to egg size (Ojanen et al. 1979, Van Noordwijk et al. 1980), but proximate factors like age (Ryder 1975, Crawford 1980, Gratto et al. 1983), laying date (Runde and Barrett 1981, Birkhead and Nettleship 1982, Bancroft 1984), and food supply (Horsfall 1984, Pierotti and Bellrose 1986) also affect egg size. Variation in egg size also may occur within clutches (Howe 1976), but this variation usually is much less than variation among females (Ricklefs 1984, Alisauskas 1986, Redmond 1986). Interspecific variation in egg composition depends largely on the precocity of the species (Ricklefs 1977, Carey et al. 1980). Yolk size, for example, increases in direct proportion to egg size in precocial (Vangilder 1981) and semiprecocial species (Alisauskas 1986), but yolk size increases less than proportionately to egg size in some altricial birds like European Starlings (Sturnus vulgaris; Ricklefs 1984) and Brownheaded Cowbirds (Molothrus ater; Ankney and Johnson 1985). The relationship between composition of eggs and precocity is fairly well established (see Carey et al. 1980), but few studies have examined intraspecific variation in egg composition that is due to proximate factors such as age, body mass, and laying date of the female. Moreover, few studies have linked egg size and composition to the size and composition of the neonate. In this study of Wood Ducks (Aix sponsa), we investigated withinand among-female variation in the size and composition of eggs. Female Wood Ducks use endogenous fat reserves to meet 88% of the lipid and energy requirements of egg synthesis, but most egg protein demands are satisfied with exogenous nutrients (Drobney 1980). Because of the dependence on lipid reserves during egg laying, a female's "decision" to reproduce may depend on reaching a 435 The Auk 104: 435-443. July 1987 This content downloaded from 207.46.13.158 on Wed, 16 Nov 2016 04:27:24 UTC All use subject to http://about.jstor.org/terms 436 HEPP ET AL. [Auk, Vol. 104 threshold level of fat reserves that may be similar among females (see Alisauskas and Ankney 1985). Therefore, we predicted for Wood Ducks that egg lipids would vary less among females than would egg proteins. We tested effects of egg mass, laying date, and body mass and age of females on variation in egg composition, and examined the effect of egg mass on structural size, body mass, and lipid reserves of day-old ducklings. Finally, we evaluated our findings in light of predictions based on optimal egg size theory (Smith and Fretwell 1974, Brockelman 1975).

Avian play: comparative evolutionary and developmental trends

Abstract: TASKER, M. L., P. HOPE-JONES, T. DIXON, &: ]•. F. BLAKE. 1984. Counting seabirds at sea from ships: a review of methods employed and a suggestion for a standardized approach. Auk 101: 567-577. WIENS, J. A., D. HEINEMANN, &: W. HOFFMAN. 1978. Community structure, distribution and interrelationships of marine birds in the Gulf of Alaska. Final reports of principal investigators, vol. 3. Boulder, Colorado, NOAA.

Phylogeny of Herons Estimated from DNA-DNA Hybridization Data

Abstract: -Genetic distances derived by hybridizing single-copy DNAs of 31 heron species (or subspecies) and 1 ibis species are summarized as ATm values. From these distances, a phylogeny is estimated and distributional properties of DNA hybridization data are computed. I found that the distinction between night and day herons is primarily adaptive, not genealogical; Syrigma is closely related to Egretta; Bubulcus and Casmerodius are closely related to Ardea, but Egretta is not; bitterns are the sister taxon of the day and night herons; Cochlearius and Tigrisoma are each others' closest relatives and together form the sister group of the rest of the ardeids; and the rate of single-copy DNA evolution differs in different heron lineages. Received 18 April 1986, accepted 3 September 1986. MOST taxonomists agree that herons belong in a family of their own, the Ardeidae, but there is considerable disagreement concerning the intrafamilial relationships of these birds. Over the last 100 years, the number of recognized species in the Ardeidae has varied from 60 to 93 and the number of genera from 15 to 35 (Sharpe 1898, Reichenow 1913). Although herons are usually divided into four groups (day herons, night herons, tiger herons, and bitterns), species are moved back and forth among these groups with each revision of the classification. A fifth group is sometimes considered necessary to accommodate the enigmatic Boatbilled Heron (Cochlearius cochlearius). The continual problems of determining most heron relationships derive primarily from the fact that adaptive changes within the limits of the ardeids' wading-piscivorous Bauplan are difficult to interpret. Herons are constrained to have long bills, legs, and necks, and this constraint has induced a family history rife with parallel and convergent evolution. To develop a hypothesis of heron phylogeny without having to interpret tracked morphological or behavioral characters, I used DNADNA hybridization to compare taxa. The logic of DNA hybridization has been reviewed by Sibley and Ahlquist (e.g. 1983), Benveniste (1985), and others. The technique operates under the assumption that the genetic relatedness I Present address: Tiburon Center for Environmental Studies, San Francisco State University, P.O. Box 855, Tiburon, California 94920 USA. of organisms is reflected in the similarity of their DNA base pair sequences. This similarity can be measured by hybridizing strands of DNA from different species and measuring the bonding strength of these hybrids. The poorer the bonding strength, the more distantly related the organisms. The advantages of DNA hybridization are that it is objective and it accounts for historically informative characteristics encoded in the DNA that are not necessarily expressed physically. Such previously unmeasurable genetic features include pseudogenes (e.g. the obsolete genes coding for tooth structure in birds; Kollar and Fisher 1980) and regulatory genes. Estimating and testing phylogenies.-DNA hybridization produces distance data, and the most appropriate method for clustering such data is least-squares regression (Sheldon in press). Templeton (1985) pointed out that tree-building algorithms based on procedures like least squares simply provide estimates of phylogenies. Alternative estimates require testing by statistical methods before one phylogeny can be accepted as better than others. Unfortunately, statistical methods for testing alternative phylogenetic hypotheses have not been established. Templeton (1985), for example, introduced the delta Q-test, but Saitou (1986) argued that this test is inadequate for differentiating topologies, and Fitch (1986) argued that it assumes evolutionary rate constancy. Although statistical procedures can be used to test for different evolutionary rates in different lineages (e.g. Felsenstein 1984) and, in special situations, can resolve multifurcations 97 The Auk 104: 97-108. January 1987 This content downloaded from 207.46.13.172 on Sat, 15 Oct 2016 05:00:21 UTC All use subject to http://about.jstor.org/terms 98 FREDERICK H. SHELDON [Auk, Vol. 104 TABLE 1. List of the taxa used in DNA hybridization comparisons and the number of separate purifications made of the DNAs of those taxa. Asterisks indicate taxa that were radio-labeled. No. of preparaSpecies tions Syrigma sibilatrix (Whistling Heron)* 1 Ardea herodias (Great Blue Heron)* 5 A. cocoi (Cocoi Heron) 2 A. pacifica (White-necked Heron) 1 A. melanocephala (Black-headed Heron) 2 A. sumatrana (Great-billed Heron) 1 Casmerodius albus egretta [Great Egret (North America)]* 6 C. a. modestus [Great Egret (Australasia)] 1 Bubulcus ibis (Cattle Egret)* 4 Egretta vinaceigula (Slatey Egret) 1 E. tricolor (Tricolored Heron) 4 E. intermedia (Intermediate Egret) 2 E. novaehollandiae (White-faced Heron) 2 E. caerulea (Little Blue Heron)* 4 E. thula (Snowy Egret)* 5 E. garzetta (Little Egret) 2 E. sacra (Eastern Reef Egret) 1 Ardeola grayii (Indian Pond Heron) 1 Butorides striatus virescens [Green-backed Heron (North America)]* 5 B. s. striatus [Green-backed Heron (South America)] 1 B. s. javanicus [Green-backed Heron (Southeast Asia)] 2 Nycticorax violaceus (Yellow-crowned Night-Heron)* 3 N. nycticorax (Black-crowned Night-Heron)* 10 N. caledonicus (Nankeen Night-Heron) 1 Cochlearius cochlearius (Boat-billed Heron)* 5 Tigrisoma lineatum (Rufescent Tiger-Heron)* 3 Ixobrychus exilis (Least Bittern)* 1 I. minutus (Little Bittern) 1 I. cinnamomeus (Cinnamon Bittern) 3 Botaurus lentiginosus (American Bittern)* 5 B. stellaris (Palearctic Bittern) 1 Plegadis falcinellus (Glossy Ibis)* 1 (e.g. Fitch 1986), none so far is useful in evaluating alternative phylogenies consisting of more than four taxa. The best way to evaluate different phylogenies is by the consensus tree method, which seeks corroboration among alternative phylogenies. Lanyon's (1985) Jackknife Strict-Consensus Tree (JST) algorithm was chosen to evaluate trees derived from subsets of the data in this study. The JST method has one additional feature. By comparing subsets of a single distance matrix, it provides an intuitive indication of the additivity and independence of the data. MATERIALS AND METHODS Biochemistry.-The methods used to prepare hybrids were essentially those of Sibley and Ahiquist (1981). Further detail is provided in Sheldon (1986). Briefly, high molecular weight DNAs were extracted from bird erythrocytes and tissues and analyzed spectrophotometrically for protein contamination. The DNAs were then sheared by sonification, yielding fragments with an average length of 400-500 base pairs, as determined by agarose gel electrophoresis. Single-copy DNA fragments were recovered by hydroxyapatite chromatography and radioactively labeled with 125I. The labeled DNAs were mixed with unlabeled driver DNAs in a ratio of 1:400, boiled, and incubated at 60?C to a Cot exceeding 15,000. These conditions permitted hybrids to form between DNA sequences differing in base pair complementarity by a maximum of 25-30%. The hybrids were then fractionated thermally at 2.5?C increments in lots of 25, from 550 to 95?C. Each 25-hybrid lot (= 1 experiment), contained at least one homoduplex control hybrid, comprising label and driver DNAs prepared from the same sample of purified DNA. The radioactivity eluted at each of the 17 fractionation temperatures, representing the amount of DNA that had dissociated to single-stranded form at that temperature, was counted in a gamma spectrometer and constituted a raw datum. Reciprocal comparisons, involving ca. 940 hybrids, were made among 13 species of heron and 1 species of ibis (Table 1). About 300 one-way comparisons were made using labeled DNAs from the same 13 heron species and driver DNAs from 18 additional heron taxa. Another ca. 130 hybrids were produced to determine genetic distances within species. In planning the reciprocal comparisons, an effort was made to hybridize the DNA of each of the 14 labeled species at least 5 times with the driver DNA of each of those species to produce 10 hybrids per pair. This was not always possible, however, because of their availability and supply. Data analysis.-The 23,000 heron raw data are available to any person who sends six formatted, IBMPC disks in a self-addressed, stamped container. Methods of data analysis differed from those of Sibley and Ahlquist (e.g. 1981, 1983) in that ATm was used as the measure of genetic distance, instead of AT50H, and clustering was performed by least squares. The logic behind the use of ATm is discussed in the Results and Discussion and that of data correction in Sheldon (in press). To calculate Tm, the count recorded at each temperature from 62.50 to 95?C was normalized to a percentage of the total counts in that range, and a cumulative frequency distribution was constructed. Tm This content downloaded from 207.46.13.172 on Sat, 15 Oct 2016 05:00:21 UTC All use subject to http://about.jstor.org/terms January 1987] Heron Phylogeny 99 equaled the temperature at which 50% of the counts was recorded, extrapolated by linear regression. Genetic distances (zvTm's) were calculated by subtracting heteroduplex Tm values from the homoduplex Tm of the same experiment. Interspecific distances were summarized in lists (Tables 2-15). The average distances between the 14 labeled taxa were calculated by multiplying the values in the lists by sample size, adding reciprocal products, and dividing the sum by the total number of observations. [A matrix of average distances was published by Sheldon (in press).] From these average distances, trees were drawn using the least-squares option of the programs "Fitch" and "Kitsch" in J. Felsenstein's phylogenetic computer package, PHYLIP (version 2.8). The relative quality of the fit of these trees was judged from the residual sum of

Predation and antipredator behavior at Guianan Cock-of-the-Rock leks

Abstract: -I documented predator attacks and antipredator behavior at four display sites of Guianan Cock-of-the-Rock (Rupicola rupicola) in Suriname from 1980 to 1985. Most observations were made at a large lek that averaged 55 territorial males, with supplemental data on display groups of 1, 2, and 6 males. Males at the main lek were attacked by 6 species of raptors, 1 mammal species, and 1 snake species. A total of 56 attacks and 2 kills by raptors were observed (0.22 attacks/day). Two kills of displaying males by the snake Boa constrictor

Multiple paternity in a wild population of mallards

Abstract: ABSTl•^CT.--Blood, heart, liver, and breast muscle samples from wild Mallard (Anas platyrhynchos) hens and their ducklings were analyzed using starch-gel electrophoresis. We found that 17.4% of the total broods sampled (n = 46) involved observable multiple mating events, that 25.8% of the sample broods involved multiple mating events when broods that were unlikely to yield information on multiple paternity were excluded (n = 31), and that a pooled maximum-likelihood estimate indicated a 60% chance that a particular duckling came from a brood that was multiply fathered, or at least 48% of broods involved multiple mating events. Received 15 January 1987, accepted $ June 1987.

Copulation and mate guarding in the Northern Fulmar

Abstract: -I studied the timing and frequency of copulation in mated pairs and the occurrence of extra-pair copulation (EPC) among Northern Fulmars (Fulmarus glacialis) for 2 yr. Copulation peaked 24 days before laying, a few days before females departed on a prelaying exodus of about 3 weeks. I estimated that females were inseminated at least 34 times each season. A total of 44 EPC attempts was seen, 9 (20%) of which apparently resulted in insemination. Five successful EPCs were solicitated by females visiting neighboring males. Multiple copulations during a single mounting were rare within pairs but occurred in nearly half of the successful EPCs. Both sexes visited neighbors during the prelaying period, and males employed a special behavioral display to gain acceptance by unattended females. Males invested time in nest-site attendance during the prelaying period to guard their mates and pursue EPC. However, the occurrence of EPC in fulmars was largely a matter of female choice. Received 29 September 1986, accepted 16 February 1987. THE occurrence and significance of extra-pair copulation (EPC) in monogamous birds has generated much interest and discussion (Gladstone 1979; Oring 1982; Ford 1983; McKinney et al. 1983, 1984). Because the males of monogamous species typically make a large investment in the care of eggs and young, the cost of being cuckolded is high, as are the benefits to the successful cuckolder. Males are expected to pursue opportunities for copulation outside the pair bond (Trivers 1972) and to reduce as far as possible the uncertainty of paternity for the young they help raise. The incidence of EPC may in general be higher in colonial species than in solitary nesters, and the threat of cuckoldry is postulated to be one of the principal disadvantages of colonial breeding (Alexander 1974, Hoogland and Sherman 1976). Mate guarding may be defined as any behavior by a mated male whose principal function is to reduce the likelihood of encounters between his mate and other males during the time when fertilization of her eggs is possible. The importance of mate guarding in the monogamous male's reproductive strategy has been recognized in a variety of species (e.g. Beecher and Beecher 1979; Birkhead 1979, 1982; Power and Doner 1980; Power et al. 1981; Werschkul 1982a; 1 Present address. Bjorkland and Westman 1983; Buitron 1983; Birkhead et al. 1985). I attempted to document the occurrence and behavioral context of extra-pair copulation and mate guarding in a colonial seabird, the Northern Fulmar (Fulmarus glacialis). Fulmars are among the longest-lived birds known, and fidelity to the same mate and nest site between years is high (Macdonald 1977, Ollason and Dunnet 1978, Hatch 1985). Only one egg is laid per clutch, and re-laying in the same season after the loss of a clutch is unknown. The sexes share about equally in incubation and chickrearing duties (Hatch 1985). Thus, fulmars exhibit a highly conservative social system. Some features of the breeding biology make this species (and perhaps other Procellariiformes) particularly interesting from the standpoint of copulation behavior and potential sperm competition. At Pacific colonies, fulmars arrive synchronously some 6-8 weeks before the first eggs are laid. There is thus a considerable prelaying period for social interaction. Foraging occurs over large ocean areas in bouts of several days, and it is difficult for males and females to coordinate perfectly their attendance patterns at the nest site. Females are receptive to copulation over the whole prelaying period, and sperm are stored in special glands in the utero-vaginal (UV) region of the oviduct (Hatch 1983). Sperm remain viable in the UV glands for several 450 The Auk 104: 450-461. July 1987 This content downloaded from 157.55.39.148 on Fri, 16 Dec 2016 07:41:35 UTC All use subject to http://about.jstor.org/terms July 1987] Copulation and Mate Guarding in Fulmars 451 weeks, as frequently there is no contact between the male and female during the "prelaying exodus" (Warham 1964), a time of continuous foraging immediately before egg laying (lasting up to 38 days in fulmars; Hatch 1985). The combination of intermittent attendance patterns, sperm storage, and a prolonged receptive period in the female renders the male fulmar particularly susceptible to being cuckolded. I studied the timing and frequency of copulation in mated pairs, both in relation to calendar date and relative to the laying dates of individual females. Social relations outside the pair bond, including EPC, were documented in a series of extended watches on a group of known individuals during 2 yr. Finally, I examined patterns of nest-site attendance during the prelaying period during 6 yr for evidence of mate guarding.