Showing papers in "The Auk in 1993"

Relationship Between Protein Nutritional Status and Immunocompetence in Northern Bobwhite Chicks

Abstract: ABSmAcr.-We investigated the effects of dietary protein quality on the development and functioning of the immune system in four-week-old Northern Bobwhite (Colinus virginianus) chicks. Chicks were fed isocaloric diets containing 8, 15, or 33% protein over a three-week period. Significant reductions in the rate of body growth were evident in chicks receiving 8 and 15% protein. Development of the bursa of Fabricius and spleen was significantly depressed in the 8% protein group compared to the other two treatments. Lymphocyte yields from dissociated lymphoid organs of chicks fed 8% protein were substantially reduced compared to birds fed higher levels of protein. In vitro lymphoproliferative responses of cultured splenocytes to mitogenic stimulation (concanavalin A, pokeweed mitogen, and Salmonella typhimurium), white-blood-cell counts, and in vivo measures of humoral immunity did not differ among dietary treatments. Cell-mediated immune function, as measured by an in vivo hypersensitivity response to an intradermal injection of a T lymphocyte-dependent mitogen (phytohemagglutinin), was significantly suppressed in the 8% protein group compared to the other two treatments. Several measures of immune-system development and function were significantly correlated with body mass change during the trial. Results indicated that four-week-old Northern Bobwhite chicks fed an 8% protein diet for three weeks may have difficulty expressing a competent immune response to pathogenic challenge in the wild. Received 30 January 1992, accepted 25 November 1992.

Foraging Strategy of Wandering Albatrosses Through The Breeding Season: A Study Using Satellite Telemetry

Abstract: Satellite telemetry of Wandering Albatrosses (Diomedea exulans) breeding on the Crozet Islands, southwestern Indian Ocean, revealed two distinct foraging strategies during successive stages of the breeding season: systematic foraging over extensive distances; and use of specific areas close to the colony. During early incubation, Wandering Albatrosses foraged over pelagic waters at an average range of 1,284 kin. The length of the foraging trips decreased towards the end of the incubation period. During the first month of chick rearing when parents brood alternately for short periods, the foraging range, distance covered, and area prospected were further reduced. Males tended to return to an individual foraging area, located at the edge of the continental shelf, that had previously been visited during the long trips of the incubation period. Females mostly prospected pelagic waters just off the shelf. After the chick had been left alone on the nest, birds exhibited a two-fold strategy, combining long foraging trips over pelagic waters with short trips over the shelf. Generally, both sexes headed for and foraged over an extensive pelagic sector. Some males also foraged over the Kerguelen shelf. Females tended to forage over more northerly waters than males. The duration of the foraging trips was most closely related to the total distance covered, but also to the maximum range during the long trips of the chick-rearing period and to a lesser extent during the incubation period. There were no such significant relationships in the case of short trips. During long pelagic foraging trips, the birds had a looping course that was determined by the wind direction, suggesting random foraging with respect to prey distri- bution. We were able to show that Wandering Albatrosses use two foraging strategies to cope with the constraints imposed by the different stages of the breeding cycle, the availability of prey, and the distribution of the prey. Use by Wandering Albatrosses of two foraging strategies may be a compromise based on the simultaneous need to satisfy the different food requirements of chicks and parents. Received 20 February 1992, accepted 23 October 1992. DURING THE breeding season, pelagic seabirds forage from a central place (often an island) and travel outward to feeding areas, where their foraging behavior is impossible to observe by island-based researchers. Heretofore, the only easily measurable feature of their foraging has been durations of foraging trips, determined from incubation bouts and chick feeding fre- quencies. Usually, it has been assumed that the duration of foraging trips depends on the dis- tance an adult has to travel from its nest to find food (Lack 1968, Pearson 1968, Croxall and

Interactions Between Stomach Structure and Diet Choice in Shorebirds

Abstract: Captive Red Knots (Calidris canutus) fed soft food pellets developed atrophied stomachs, and were reluctant to eat their usual hard-shelled mollusc prey. An interspecific comparison among shorebirds showed that wild Red Knots and other intact-mollusc-eating species have gizzards with relatively great mass but very small proventriculi. Within six different shorebird species, the heavier individuals usually had the heavier stomachs as well, but in Red Knots and Bar-tailed Godwits (Limosa lapponica) we identified heavy premigrant individuals with reduced stomach masses, suggesting a reallocation of protein reserves before long-distance flights. In both species reduced stomach mass was associated with a relatively soft diet. We were unable to show that during adjustment of stomachs to hard-shelled prey, such prey are broken down to smaller fragments. We attribute this to the counteractive influence of the pylorus during adjustment. We summarize the suggested stomach/diet interactions as a network of causal relationships and feedback loops involving the type of diet and gizzard mass. We identify two basic modifiers of gizzard mass: one working via endurance training and disuse atrophy; and another involving endocrine and/or neural mechanisms. It is likely that, in the course of their annual cycle, shorebirds are prevented from achieving maximal digestive performance owing to seasonal changes in feeding habitats and diet enforced by their long-distance migrations.

Habitat Heterogeneity and Life-History Variation of Mediterranean Blue Tits (Parus Caeruleus)

Abstract: -The extensive variation in breeding traits of Mediterranean Blue Tits (Parus caeruleus) is hypothesized to result from large differences in the timing and abundance of food resources, depending on whether the dominant tree species of the habitat is deciduous (Quercus pubescens) or evergreen (Q. ilex). Data were collected on tree phenology, food abundance (caterpillars), and breeding traits of tits in one mainland deciduous habitat, two mainland evergreen habitats, and one evergreen habitat on the island of Corsica. In the mainland deciduous habitat, an early breeding time and a large clutch size were associated with an early and abundant food supply. In the evergreen habitats (both on mainland and on Corsica), the leafing process occurred three weeks later and the abundance of caterpillars was much lower. On Corsica, tits started to lay three weeks later than in the deciduous mainland habitat and laid about 30% fewer eggs. As in the deciduous mainland habitat, the breeding process seemed to be adjusted to the patterns of food availability. In the two mainland evergreen habitats, tits started to breed earlier and laid more eggs than expected from the patterns of food availability so that they mismatched the best period to raise their young. The apparent maladaptation of tits in these evergreen mainland habitats is hypothesized to result from an asymmetric gene flow between rich deciduous habitats (source), where well-adapted birds produce many fledglings, and poor evergreen habitats (sink), where the density is maintained through immigration from rich habitats. Received 4 February 1992, accepted 20 November 1992. MANY PARTS of the Mediterranean region are "checkerboard" landscapes with a large variety of habitats due to small-scale heterogeneity in such factors as altitude, geological substrate, isolation, and especially variation in dominant tree species (deciduous broad-leaved, evergreen broad-leaved, coniferous). In addition, land-use practices have contributed greatly to the mosaiclike pattern of many Mediterranean landscapes. Because the Blue Tit (Parus caeruleus) occurs in many forest types and has been extensively studied across its range, this species is a good model for evaluating the extent to which life-history traits are adapted to local environments. Large variation occurs in breeding traits of Blue Tits over their range (Fig. 1). On average, birds start to breed earlier and have a lower clutch size (with a larger among-habitat variation of these traits) in the Mediterranean region than in central and northern Europe (Fig. 1). For example, the Mediterranean includes populations that have the earliest (21 March; population 14 on Fig. 1) and among the latest (11 May; population 22) onsets of breeding in Europe. Patterns of variation in laying date and clutch size of the Blue Tit at 12 Mediterranean study sites in the Mediterranean bioclimatic region, ranging from the Canary Islands to the northern limit of the Mediterranean, show some regular trends (Table 1): (1) three populations in deciduous oakwoods have the largest clutch size and start to breed early; (2) populations in evergreen oakwoods have a smaller clutch size and breed later in season; and (3) some populations in evergreen oakwoods breed extremely late and have a very small clutch size, especially those that are isolated on islands (Canary Islands, no. 13; Corsica, no. 22). There is an inverse relationship between laying date and clutch size (r = -0.729, P = 0.003, n = 15). Because food supply has consistently been shown proximately and ultimately to determine important breeding traits such as laying date and clutch size (Lack 1966, Klomp 1970, Drent and Daan 1980, Ricklefs 1983, Martin 1987, Perrins and McCleery 1989, Zandt et al. 1990), we hypothesize that the large among-habitat variation of breeding traits in the Mediterranean region represents a response to large variation in the food supply. Evergreen trees renew but a fraction of their foliage (ca. 30%) yearly, since their leaves are photosynthetically active for several years (three years in the Holm oak, Quercus ilex; Floret et al. 1989). By comparison with deciduous oaks that renew their whole foliage each year, this Dat-

Habitat fragmentation and pairing success in the ovenbird (seiurus aurocapillus)

Abstract: ABSTRACr.-In 1990 and 1991, we determined the proportion of Ovenbird (Seiurus aurocapillus) territorial males that were paired in a 25-ha plot in an extensive forest (>350 kM2) in Quebec, and compared it to pairing success in populations breeding in nearby forest fragments (4.5-53.0 ha) in Quebec and Ontario. We tested the hypotheses that pairing success would increase with population density, and decrease with the degree of fragmentation of the habitat. Pairing success was higher in the extensive forest in both years, although the difference was only marginally significant (P 0.25) in 1991 (76.5 vs. 58.3%). The density of territorial males was twice as high in the extensive forest as in the forest fragments. When including data from similar studies conducted in New Jersey and Missouri, we found that pairing success increased and gradually levelled off with the density of territorial males. Although we lacked a common parameter for measuring habitat fragmentation across all three studies, pairing success appeared to decrease with the isolation of forest fragments from surrounding woodland, while it remained stable around 80% in extensive forests of all three studies. The effect of habitat fragmentation on pairing success was particularly severe in the Missouri study area, at the periphery of Ovenbird's breeding range. A general linear model showed that woodland configurationthe location of a study site in an extensive or fragmented forest-was the best predictor of pairing success, and that geographical location also had a significant effect. We conclude that habitat fragmentation reduces pairing success by altering dispersal dynamics or habitat selection by females. Received 6 April 1992, accepted 17 November 1992. THE OVENBIRD (Seiurus aurocapillus) has been

Territorial exclusion by a long-distance migrant warbler in jamaica: a removal experiment with american redstarts (setophaga ruticilla)

Abstract: To test whether male American Redstarts (Setophaga ruticilla) excluded conspe- cifics from selected habitats on their wintering grounds, we removed territorial individuals from four replicate sites in two different habitats in Jamaica, West Indies, and recorded territory shifts and new colonizations of the vacated areas. In total, 12 American Redstarts (nine after-hatch-year (AHY) or older males, two yearling (HY) males, and one female) were removed, and their vacated territories were re-occupied by 18 neighboring or newly-ap- pearing redstarts (five AHY males, four HY males and nine females). The re-occupation of the vacated areas supports the hypothesis that territoriality in this species acts to exclude conspecifics from certain winter habitat, and shows that American Redstarts compete with conspecifics for habitat in their winter grounds. Moreover, a statistically significant shift in sex composition following removal indicates that AHY males excluded females from mutually acceptable habitats. Such behavioral dominance, if confirmed, could help account for sexual habitat segregation during winter, and could result in differential winter survival rates between the sexes, thereby influencing population structure and regulation in this long- distance migrant. Received 10 August 1992, accepted 15 December 1992.

Mitochondrial-dna variation and evolutionary relationships in the amakihi complex

Abstract: AssRAcT.-An analysis of restriction-site variation in mitochondrial DNA was conducted to examine relationships among five taxa in one group of honeycreepers-the amakihi complex (genus Hemignathus). We analyzed 35 ingroup and 3 outgroup samples. Tree topologies, based on both distance and parsimony methods, grouped taxa into two distinct lineages: the virens-wilsoni lineage; and the chloris-stejnegeri-parvus group. Inter-island sequence divergence (average d,X = 0.0368) is considerably higher than intra-island variation (mean d, = 0.0035), and is higher than average for avian species. Variability (measured as both nucleotide diversity and maximum divergence between haplotypes) differs among island populations. Molecular evolutionary rates were calibrated on the basis of maximum island age estimates; sequence divergence in this lineage is approximately 2% per million years. The relationships within the chloris-stejnegeri-parvus clade generally are consistent with the previously proposed model of double invasion. Genetic distances and the pattern of relationships among amakihi taxa indicate that species status for H. v. chloris and H. v. stejnegeri may be warranted. Received 15

Clutch-Size Determination in Precocial Birds: A Study of the Common Eider

Abstract: -Clutch-size determination in the Common Eider (Somateria mollissima) was evaluated in a colony in northern Norway. Females in good body condition (determined from mass at hatching) produced large clutches and had a shorter incubation period than females with small body reserves. Females in good body condition cared for young (including adoption of the young of other females), while females in poor body condition abandoned their young soon after hatching. Repeatability (an upper limit to heritability) of clutch size, which for individual females varies from three to six eggs, does not differ significantly from zero. A hypothesis is proposed, suggesting that there is a trade-off involved in allocating body reserves to eggs, incubation, and care of chicks and that females use a particular clutch-size strategy related to their body condition and ability to care for young. Received 8 May 1992, accepted 12 May 1993. LACK (1947, 1948) SUGGESTED that clutch size in altrical birds was ultimately limited by the ability of the parents to rear young. Although Lack's hypothesis has been somewhat modified (see Williams 1966, Charnov and Krebs 1974, H0gstedt 1980), the idea of brood-size limitation has been supported by many studies (for reviews, see Klomp 1970, Dijkstra et al. 1990). The adaptive significance of clutch size in birds with self-feeding precocial young is an enigma (Arnold and Rohwer 1991). Clearly, Lack's hypothesis for clutch-size determination in altricial birds cannot apply to precocial birds. A number of other hypotheses have been proposed (see Winkler and Walters 1983). The one most often applied is the egg-production hypothesis (Winkler and Walters 1983, Arnold and Rohwer 1991). This hypothesis was proposed by Lack (1967, 1968), who suggested that clutch size ultimately is limited by the hen's ability to allocate nutrient reserves to egg laying. However, except for studies on arctic-nesting geese (Ankney and MacInnes 1978), evidence corroborating the hypothesis is scarce. A number of studies have shown that female waterfowl use body reserves for egg production (Ankney et al. 1991). However, use of body reserves for egg production has uncritically been used as evidence that available body reserves determine the optimal clutch size (Arnold and Rohwer 1991). Even if nutrient reserves influence number of eggs produced, there may be a trade-off between the use of body reserves for egg production and for later use during incubation (Erikstad 1986, Gloutney and Clark 1991) and care of chicks (Lessells 1986, Bustnes and Erikstad 1991). In this study we examine some of the hypotheses that have been put forth as possible explanations for within-season variation in clutch size. We outline a new hypothesis that combines several earlier ideas to show that clutch-size determination could be affected by an interaction of female body condition, egg predation, and parental care. MATERIALS AND METHODS The study was carried out in a Common Eider (Somateria mollissima) breeding colony near Troms0 in northern Norway (69?49'N, 18?15'E) in 1986-1989. The colony was on a 0.65-km2 island (Grind0ya) and contained 400 breeding pairs. Searches were begun in early May when first nests were initiated. Nests were visited at oneor two-day intervals to determine laying dates and clutch sizes. A clutch was assumed to be complete and incubation to have begun when no new eggs were recorded during a period of three days. We determined intraspecific nest parasitism by detecting multiple eggs laid in a nest within 24 h. The frequency was very low (less than 1%; unpubl. data). All parasitic clutches were excluded from the analysis. Incubation was assumed to begin on the day that the final egg was laid and was completed when one chick had hatched. Females were caught on the nest with a net at hatching and weighed using a spring balance (? 10 g). For a few females caught three to five days before hatching, we estimated hatching mass by using a daily mass

Living with parasites: prevalence of a blood parasite and its effect on survivorship in the purple martin

Abstract: -We studied the prevalence of the blood parasite Haemoproteus prognei (Haematoprotozoa) from 1986 to 1990 in a breeding colony of Purple Martins (Progne subis) in Maryland and in overwintering martins in three Brazilian roosts in 1990. Yearling breeders were infected at a significantly lower rate than adults, and no yearlings in wintering roosts were infected. Haemoproteus prognei might be more virulent in immunologically naive birds and cause high mortality in young birds during the stress of their first migration. Many birds became infected over three years and most maintained a chronic infection. Infected birds returned to the colony with the same frequency as uninfected birds. Infected adults tended to arrive at the breeding site ahead of uninfected adults. Clutch size did not differ, but uninfected females had lower breeding success than infected individuals. We discuss the evolutionary implications of high mortality coupled with superior breeding success in chronically infected birds, whose immune system has been "tested" for parasite resistance, and suggest an alternative to the predominant view that parasite resistance means avoiding them altogether. Received 2 March 1992, accepted 27 July 1992. THE DEBILITATING effects of parasites underlie many recent theories in evolutionary biology. They have been implicated in regulating vertebrate host populations (Anderson and May 1978, 1979, May and Anderson 1979, 1983), in sexual selection (Hamilton and Zuk 1982, Jaenike 1988, Zuk 1991), in the evolution of sex (Hamilton 1980), and in ecological and behavioral changes in host populations (van Riper et al. 1986). Parasites have potential effects on the survival and fitness of hosts (Ewald 1983, Atkinson and van Riper 1991). Chronic parasitic infections may cause nutritional stress and mortality by decreasing the foraging ability of an infected animal (Brooke 1945, Park 1948, Chandler 1953, Jenkins et al. 1963), and affect host mating success (Jenkins et al. 1963, Dolinsky et al. 1981, Freeland 1981, Rau 1983, Borgia 1986, M0ller 1990). Infected individuals might be more susceptible to predation than healthy individuals in a population (Van Dobben 1952, Holmes and Bethel 1972, Vaughn and Coble 1975). In injured raptors, hemoprotozoal infection prolongs the rehabilitation time necessary before release (Olsen and Gaunt 1985). In contrast, parasitologists tend to emphasize coevolution between parasite and host (Holmes 1983, Hafner and Nadler 1988, Toft 1991) and suggest that most parasitic infections in vertebrates are relatively benign (Bennett et al. 1988, Cox 1989). Furthermore, several studies have not found debilitating effects of blood parasites on their avian hosts (e.g. Weatherhead and Bennett 1991, 1992). Here, we show that both hostdebilitating and host-benign views of parasitic infection are probably correct, even within the same host-parasite interaction. We emphasize that, in defining what is meant by parasite resistance, avoiding blood-parasite infection may not be as evolutionarily important to vertebrate hosts as overcoming, and living with, infection. We initiated a study in 1986 to understand the effects of internal parasites on the survival and lifetime reproductive success in Purple Martins (Progne subis). Purple Martins breed colonially in North America and winter in Brazil (AOU 1983). Allen and Nice (1952) described their breeding biology, and Morton and Derrickson (1990) discussed migration arrival schedule. Here we describe the prevalence of a malarialike protozoan parasite, Haemoproteus prognei, in the Purple Martin. Haemoproteus prognei also infects the Lesser Striped Swallow (Hirundo abyssinica), the Red-rumped Swallow (H. daurica), and the Barn Swallow (H. rustica) in Africa and Southeast Asia, but the Purple Martin is the only host known in the Western Hemisphere (White and Bennett 1978). The vector is unknown, probably a biting midge (Culi-

Long-Term Dynamics of a Wood Thrush Population Breeding in a Forest Fragment

Abstract: ABsmAcT.-The dynamics of a population of Wood Thrushes (Hylocichla mustelina) in a Delaware woodlot from 1974 through 1990 did not meet all predictions of the forest-fragmentation hypothesis, which posits that declining abundance of Neotropical, migratory, forest songbirds results from poor reproduction in, and immigration to, forest fragments. Abundance declined at an average rate of 4% per year over the period 1978 through 1987, equalling the national decline found by the Breeding Bird Survey for those years, but recovered by 1990 to pre-decline levels. Abundance of previous residents followed a similar pattern, the only population component to do so. Abundance of new immigrants and of returning, locally produced young was generally stable. Throughout the study, reproductive rates were high enough to maintain the population at the return rates observed early and late in the study. However, a sustained episode of reduced production per female and of an increased percentage of adults failing to produce any young generally coincided with the decline in abundance. When the failure rate later dropped, return rate and abundance subsequently increased. We conclude that a period of elevated, predation-caused failure prompted greater emigration by an ever-younger, less-site-faithful population. High emigration coupled with stable immigration, stable recruitment of local young, and even normal mortality of residents would yield a declining population. A regional predation episode could cause a broader decline in abundance through several mechanisms that could reduce the number of available immigrants. Received 25 March 1991, accepted 9 November 1992.

Patterns of predation on passerine nests in marshes: effects of water depth and distance from edge

Abstract: We tested a hypothesis that the high densities of some passerines breeding in North American marshes result from greater safety of this habitat from predators as compared to upland habitats. We examined the relative importance of water depth and distance from the marsh edge in lowering predation rates on experimental nests with Blue-breasted Quail (Coturnix chinensis) eggs. In addition, using cameras we studied the role of water depth in determining the predator community. Our results showed that: (1) predation was lower in the marsh than in the adjacent upland; (2) predation rates decreased with increasing water depth in the marsh; (3) for the marsh nests, the distance to the marsh edge was relatively unimportant; (4) the diversity of nest predators decreased with increasing water depth; and (5) in the deep marsh areas, there was only one major predator, the Marsh Wren (Cistothorus palustris). We propose that the greater safety of deep-water marsh areas, the reduced com- plexity of the predator community, and the type of predators allowing effective nest defense by nest owners have played the key role in the evolution of reproductive strategies of marsh- nesting passerines. Received 10 October 1991, accepted 15 June 1992. NORTH AMERICAN marshes are among the most productive habitats that also accommodate a di- verse avian community (Verner and Willson 1966). Some passerines, such as the Red-winged Blackbird (Agelaius phoeniceus), Yellow-headed Blackbird (Xanthocephalus xanthocephalus), and Tricolored Blackbird (A. tricolor), breed in marshes in high densities (e.g. Orians 1961, 1980), suggesting that marshes are highly suit- able for these birds. This high suitability of marshes could be explained in terms of food abundance (e.g. Verner and Willson 1966, Or- ians 1980) and/or reduced nest predation (e.g. Robertson 1973, Wittenberger 1976). Food available on territories of the above blackbirds however, is relatively unimportant because in- dividuals of all three species usually forage away from their territories (e.g. Orians 1980). On the other hand, water in marshes should prevent most of the typical terrestrial predators from reaching passerine nests located especially in the deeper marsh areas. This presumably lower vulnerability of deep-water marshes to preda- tors should lead to intense competition among birds for these "safe" breeding grounds. Given these reasons, we have evaluated the effect of

Intergeneric Phylogenetic Relationships of Swallows Estimated by DNA-DNA Hybridization

Abstract: -The phylogeny of the subfamily Hirundininae was estimated by hybridizing single-copy nuclear DNAs of 21 swallow species, representing 19 former and current genera, and a Tufted Titmouse (Parus bicolor) as outgroup. The phylogeny, which was unusually well resolved, consisted of three fundamental clades: Hirundo and allies, core martins, and African sawwings. The clade of Hirundo and allies comprised Hirundo rustica, Ptyonoprogne fuligula, Delichon urbica, Cecropis semirufa, Petrochelidon pyrrhonota, and P. spilodera. The sister-group of Hirundo and allies was the core martin clade, which consisted largely of endemic New World taxa (Pygochelidon cyanoleuca, Neochelidon tibialis, Atticora fasciata, Phaeoprogne tapera, Progne chalybea, Haplochelidon andecola, Stelgidopteryx ruficollis, and Tachycineta bicolor) and some basally branching Old World groups (Riparia riparia, R. cincta, Phedina borbonica, Pseudhirundo griseopyga, and Cheramoeca leucosternus). The African sawwings (represented by Psalidoprocne holomelas) formed the sister group of the core martins and Hirundo and allies. Among some interesting discoveries, we found a close relationship between the monotypic African and Australian genera Pseudhirundo and Cheramoeca. We also found that Delichon, which has persisted in the nomenclature as a genus separate from Hirundo, is monophyletic with taxa that are commonly considered to be members of Hirundo. On the other hand, Haplochelidon andecola, which is often considered to be a Hirundo or Petrochelidon, is not closely related to those genera, but instead lies among the New World members of the core martin clade. Received 1 July 1992, accepted 25 November 1992. PERHAPS NO FAMILY of passerines is as uniform morphologically and diverse generically as the swallows (Hirundinidae). All swallow species conform to a fundamental body plan that includes long and pointed wings, medium length tails, short legs, and bills that are short and wide. This uniformity is the likely result of adaptation to a strictly aerial insectivorous lifestyle. Apparently because of this uniformity, systematists have been loath to attempt a phylogenetic reconstruction of the swallow family as a whole. While there have been many classifications of the Hirundinidae (e.g. Sharpe 1885, Peters 1960, Turner and Rose 1989, Sibley and Monroe 1990) and many discussions of the systematics of individual species or small groups of taxa, only one published paper has considered the familywide relationships of swallows based on evolutionary or phylogenetic logic. This is the 50-year-old study of Mayr and Bond

Use of an Exotic Tree Plantation by Bornean Lowland Forest Birds

Abstract: ABsTRAcr.-During May to July 1982, we surveyed birds in primary forest and in differentaged groves of the exotic tree Albizia falcataria at Sabah Softwoods, a lowland tree plantation in Sabah, East Malaysia (formerly British North Borneo). We found that the Albizia was in general attractive to many native birds. About 60% of primary-forest species used the plantation, and the frequency at which individuals were observed in the oldest groves was almost twice that of nearby primary forest. The Albizia attracted birds because, as an extremely fastgrowing legume with thin leaves, it permitted the rapid development of a well-structured secondary forest. It also was heavily infested with pest insects, which provided an abundant food source. Despite its apparent richness, however, the Albizia lacked several important features of natural forest (e.g. canopy fruits and nest holes). As a result, some primary-forest bird groups were poorly represented (e.g. large canopy frugivores and flycatchers) and others could make only limited use of the plantation (e.g. woodpeckers). In addition, the Albizia is expected to lose its diversity as the plantation as a whole ages. Many of the plantation birds were transients from nearby forest that visited daily to feed, and some probably had been displaced by intense logging. The number of daily transients should decrease as primary forest recedes due to logging and development. Refugee species diversity should suffer from attrition as the plantation is cropped and predation and age take their toll. Received 9 March 1992, accepted 20 November 1992.

Sperm Competition and the Reproductive Anatomy of Male Superb Fairy-Wrens

Abstract: ABSTRAcr.-In Superb Fairy-Wrens (Malurus cyaneus), groups of males cooperate with a single female to rear young, yet offspring are usually sired by males from outside the group. In this unusual mating system there is potential for intense sperm competition. During the breeding season, males develop a sperm storage structure (cloacal protuberance) and testes that proportionally are among the largest found in passerines. We compared the development pattern and size of cloacal protuberances of males differing in age and social status. Protuberance size increased with body mass. Age, intragroup dominance, and pairing status did not influence the overall size of the protuberance, but old males had a larger tip on their protuberance. This prominent tip has not been reported in other species, and we speculate that it serves as an intromittent organ. Other birds with large testes and cloacal protuberances have high copulation rates, but copulation in Superb Fairy-Wrens is only very rarely observed. We propose that the cloacal protuberance and large testes of Superb Fairy-Wrens provide large sperm reserves primarily for extrapair copulations. These may occur frequently, or involve the transfer of large ejaculates. Received 13 January 1993, accepted 14 March 1993.

Inheritance of egg-color polymorphism in the village weaver (Ploceus cucullatus)

Abstract: --Eggs collected from an aviary colony of Village Weavers (Ploceus cucullatus cucullatus) over a 14-year period varied in color among different females from white to emerald or turquoise, and from many spots to few or none. Color and amount of spotting of the eggs of a given female were constant throughout her life (based on 815 eggs from 37 females). Color was judged from the Villalobos Color Atlas. Mendelian analysis of five different hypotheses showed that inheritance of background color of eggs in 20 different crosses was consistent only with a hypothesis of two independent pairs of autosomal alleles for hue. Received 14 September 1992, accepted 25 November 1992. THE EDITORS of a recent book on avian genetics pointed out that, despite widespread interest among ornithologists in plumage polymorphism, evidence of the genetic basis for most of these polymorphisms is sadly lacking (Cooke and Buckley 1987:202). Even less is known about the genetic control of egg-shell-color polymorphisms. My objective is to present evidence on Mendelian inheritance of egg-shell-color polymorphism in a passerine bird. In the domestic fowl (Gallus gallus) for which the first demonstration of Mendelian heredity in the animal kingdom was made by William Bateson (Punnett 1923), a Mendelian analysis of egg-shellcolor polymorphism was done long ago (Punnett and Bailey 1920, Punnett 1923, 1933a), and this classic work is still one of the few published records dealing with this problem (Washburn 1990). There is no reference in the literature giving comparable evidence for any passerine bird. In North America the color of eggs is generally consistent for a given species of bird, and this is particularly true of the passetines (Harrison 1978). This is in strong contrast to the genus Ploceus (Ploceidae, weaverbirds) in which variation in egg color within the species is higher than in any other group of birds (Moreau 1960:446). In the Village Weaver (Ploceus cucullatus) of sub-Saharan Africa, the eggs are among the most variable in color and pattern of any ploceid species (Meise 1983:521). The different races of the Village Weaver have similar variations in egg color and pattern, in which ground color varies from white through blues to greens, and from plain eggs to eggs spotted to varying degrees usually with brown or reddish brown. This pattern of variability is seen in eastern (Mackworth-Praed and Grant 1960), central (Chapin 1954), western (Bannerman 1949), and southern (Maclean 1985) Africa. Bannerman (1949:94) further noted for the Village Weaver: "Only one type of coloring ap-

Plasma corticosterone, adrenal mass, winter weather, and season in nonbredding populations of Dark-eyed Juncos (Junco hyemalis hyemalis)

Abstract: Plasma levels of corticosterone (B) have been measured in free-living Dark- eyed Juncos (Junco hyemalis hyemalis) wintering in Michigan, Indiana, and Tennessee. Total adrenal dry mass also was determined for a large number of wintering juncos collected at these three locations. All populations had access to supplemental food. When Michigan, Indiana, and Tennessee winter populations were compared, plasma B was significantly greater when new snow had fallen on trap days (midwinter) than when it had not (early winter). However, the relative importance of a direct response to proximate snowfall and a seasonal change as independent causes of this pattern could not be determined. In the Tennessee population in early January, plasma B was greater on two days with new snowfall than on two days without new snowfall. Total adrenal dry mass was significantly and positively correlated with recent snowfall, possibly in support of elevated plasma B on snowy days. Together with studies showing increased fat reserves shortly after new snowfall in the Dark- eyed Junco, these results suggest that corticosterone might be involved in directing increased feeding and associated lipogenesis as inclement weather sets in. Although a direct response to snowfall is suggested, factors correlated with snowfall (e.g. barometric pressure) also may cause elevated titers of B during inclement weather. Received 14 October 1991, accepted 4 March 1992.

Genetic divergence among populations of a tropical passerine, the streaked saltator (Saltator albicollis)

Abstract: --We analyzed mitochondrial-DNA (mtDNA) restriction-site variation in populations (subspecies) of the Streaked Saltator (Saltator albicollis) in Panama, Peru, and the Lesser Antilles. Genetic differentiation between populations (Panama vs. Peru, 0.035; Lesser Antilles vs. Panama/Peru, 0.063) greatly exceeded values reported for populations or subspecies within North American bird species (0.0028-0.0086), and was near the high end of the range reported for congeneric species of passerine birds (0.016-0.073). Nucleotide diversity within populations was similar to that reported for other species of passerines and did not differ markedly between mainland and island populations. Thus, founder effects and population bottlenecks associated with island colonization appear to have caused little, if any, loss of mtDNA nucleotide diversity. No significant mtDNA differentiation was observed between populations of named subspecies on mainland Panama (S. a. isthmicus) and the Pearl Islands (speratus), or between two subspecies in the Lesser Antilles (albicollis and guadelupensis). Saltator albicollis exhibits marked geographical genetic differentiation, as assayed by mtDNA polymorphism, but this bears little relationship to subspecies distinctions. Finally, the genetic data suggest that Antillean populations of Streaked Saltators should be distinguished at specific rank (S. albicollis), with continental forms referred to S. striatipectus. Received 7 May 1992, accepted 14 August 1992. MITOCHONDRIAL-DNA (mtDNA) sequence divergence based on restriction-site analysis (Avise et al. 1987, Dowling et al. 1990) has provided informative measures of genetic differentiation within avian species and genera (Mack et al. 1986, Avise and Zink 1988, Ball et al. 1988, Zink and Avise 1990, Quinn et al. 1991, Zink 1991, Zink and Dittmann 1991, Zink et al. 1991a, b, Bermingham et al. 1992). With regard to North American passerine birds, for example, mtDNA divergence between species is almost an order of magnitude greater than differences among populations within species. These findings refer exclusively to temperate taxa. At present, there is little information available on mtDNA divergence among populations of tropical birds, although allozyme surveys (Capparella 1988, Peterson et al. 1992) have revealed marked genetic differentiation over short distances within several groups of Amazonian and Mexican pas3 Mailing address: Smithsonian Tropical Research Institute, Unit 0948, APO, AA 34002-0948, USA. 4 Present address: Illinois Natural History Survey, 607 East Peabody Drive, Champaign, Illinois 61820, USA. serines. Additionally, Escalante-Pliego (1991) has documented substantial isozyme differences among disjunct populations of yellowthroats (Geothlypis) in Central and South America, and Hackett and Rosenberg (1990) have demonstrated pronounced geographical subdivision and differentiation in Neotropical antwrens (Formicariidae). Appraisals of genetic differentiation among populations of tropical birds would address questions of population structure and incipient species formation in regions of high species richness. Tropical species diversity is thought to result from high rates of species production, low rates of extinction, or great age of tropical regions. Species production presumably varies in relation to rate of evolutionary change within populations and degree of population subdivision. Estimates of mtDNA divergence directly address the issues of population subdivision and the relative genetic differentiation of taxa of specific rank. It has been suggested that the constant temperatures and diminished seasonal change in climate in the tropics have led to increased ecological specialization, increased fragmentation of species

Use and importance of feathers as nest lining in tree swallows (Tachycineta bicolor)

Abstract: Tree Swallows (Tachycineta bicolor) commonly line their grass nests with feath- ers of other species. In one of three years studied, there was a significant negative correlation between numbers of feathers in the nest and chick nestling periods (i.e. broods surrounded by more feathers fledged earlier). In the third year of the study, the population was divided into two groups, balanced for all measurable aspects of parental quality. In the "removal" group, all feathers were removed daily and in the "control" group all feathers were allowed to remain. All nests and their contents were disturbed equally. Chicks in removal nests had lower growth rates (in mass, wing chord and tarsus) and higher infestations of mites and lice. I suggest that feathers aid chicks directly by preventing hypothermia and indirectly through higher growth rates by allowing earlier fledging when necessary. Protection from ectoparasites may be an important advantage in natural nests where nest cavities are not cleaned out annually. Inadvertent removal of feathers from nest boxes may be an important cause of posthatching declines in feather numbers. Received 19 July 1991, accepted 14 August 1992. TREE SWALLOWS (Tachycineta bicolor) usually line their nests with feathers, and one of the most conspicuous and distinctive behaviors during this swallow's breeding season is the frequent contests over feathers. These contests involve high-speed aerial chases accompanied by considerable aerial jostling and bodily con- tact, often involving several birds (e.g. Wey- demeyer 1934, Kuerzi 1941; for an illustration see Audubon (Peterson and Peterson 1981:plate 276)). Having been intrigued by these aerial contests and the apparent worth of the resource being contested, I began a study of the feathers used in Tree Swallow nests in 1987. I present here a brief description of the natural history of the use of feathers as nest lining, some cor- relative evidence of the feathers' importance, and the results of an experimental study doc- umenting the effect of feathers in the nest on chick growth and ectoparasite infestations. The nest linings of birds generally have been thought to provide insulation for the devel- oping offspring (e.g. Haftorn 1978, Capreol 1983, Moller 1984) or protection against ectoparasites (e.g. Wireberger 1984), and my experiment test- ed the two predictions that feather relnoval would lead to: (1) decreased chick growth and/ or survival; and (2) increased numbers of ec- toparasites. METHODS

Application of Genealogical-Concordance Principles to the Taxonomy and Evolutionary History of the Sharp-Tailed Sparrow (Ammodramus caudacutus)

Abstract: -We examined geographic differentiation in mitochondrial (mt) DNA and in morphometric characters among 12 populations of the Sharp-tailed Sparrow (Ammodramus caudacutus) representing all recognized subspecies and geographic regions. Both data sets reveal the existence of two distinct groups of populations, a northern group from the Canadian maritime provinces and Maine, the St. Lawrence Valley, Hudson Bay lowlands, and interior prairies, and a southern group from along the Atlantic coast north to southern Maine. In one sample from southern Maine, both forms co-occur, and about 40% of the individuals there appear to be of hybrid ancestry. Recently, principles of genealogical concordance have been proposed as a conceptual basis for recognition of biological taxa. Here we provide an empirical application of these principles in the context of observed concordance between the mtDNA phylogenetic partition and the subdivisions evidenced by morphological (and behavioral) attributes in the Sharp-tailed Sparrow complex. We recommend that two subspecies of A. caudacutus be recognized: one (A. c. nelsoni) to encompass the northern populations (formerly A. c. nelsoni, A. c. alterus, and A. c. subvirgatus); and the other (A. c. caudacutus) to encompass the southern populations (formerly A. c. caudacutus and A. c. diversus). By taxonomically formalizing what appears to be a fundamental phylogenetic partition among Sharp-tailed Sparrow populations, study of the biogeographic history, reproductive relationships, and management of the forms will be facilitated. Received 26 March 1992, accepted 23 November

A generalized discriminant for sexing fulmarine petrels from external measurements

Abstract: ABsTRAcr.-Discriminant analysis can use morphometric differences between known male and female birds to predict the sex of unknown individuals in field studies. Geographic variation in size and shape often limits the predictive value of a discriminant function to the population from which it was derived. Specific discriminant functions for populations of five species of fulmarine petrels (Northern Fulmar, Fulmarus glacialis; Southern Fulmar, F. glacialoides; Antarctic Petrel, Thalassoica antarctica; Cape Petrel, Daption capense; and Snow Petrel, Pagodroma nivea) assigned 81 to 98% of birds in the samples to the correct sex, but the validity of each discriminant applied to alternative populations remained questionable. Our approach to overcome this limitation is to combine data from the different species into a single discriminant. Adequate performance of this generalized discriminant in samples of different species shows its validity for use in other populations of any of these species. The generalized function calculates the discriminant scores for individual fulmarine petrels as: Y = HL + 2.38BD + 0.41TL 0.21CL, where HL is head length, BD is bill depth, TL is tarsus length and CL is bill length (measurements in millimeters). The cut point to split sexes is different in each sample and may be calculated directly from discriminant scores, without reference to sexed birds, by using a maximum-likelihood method. Depending on species, the generalized method results in 84 to 97% correct classifications and can be applied to other populations of fulmarine petrels without requiring samples of birds of known sex. Received 19 November 1991, accepted 20 November 1992.

Age-specific fecundity in european blackbirds (turdus merula): individual and population trends

Abstract: We studied age-related variation in fecundity in six cohorts of European Black- birds (Turdus merula) in Cambridge, United Kingdom. Clutch-initiation date, breeding-season length and clutch size varied significantly with age. First-year females started breeding the latest, had the shortest breeding seasons, and had the smallest clutches. Fecundity varied with female age in a nonlinear way; on average, clutch-initiation dates were earliest at the age of 3.7 years, and breeding-season length peaked at 3.6 years of age. Clutch size increased gradually in the range of ages considered (one to six years). After controlling for year effects, significant variation in the age-fecundity relationships remained among cohorts. Longitudinal analyses showed that the increase in fecundity was mainly the result of individuals' intrinsic changes. Given females started breeding earlier, had longer breeding seasons, and laid larger clutches as they became older, independently of the age of their mate. After controlling for the age of their mate, given males showed no increase in fecundity with age. Logit analyses failed to detect positive relationships between the fecundity of first-year females and their survival to the next breeding season. Thus, the increase in fecundity with female age was more the result of intrinsic individual causes than of natural selection resulting in an increased proportion of high-fecundity individuals among older birds in the population. Received 21 November 1991, accepted 27 May 1992.

Seasonal Changes in Body Mass and Use of Torpor in a Migratory Hummingbird

Abstract: -In a study designed to determine seasonal patterns of body mass and torpor in Rufous Hummingbirds (Selasphorus rufus), birds were maintained for 12 months in the laboratory on a photoregime approximating that experienced by free-living birds. Ambient temperature cycled from 20?C during the day to 5?C at night. Body mass, torpor, and rates of nighttime oxygen consumption were measured under conditions of ad libitum feeding in LD 12:12 in autumn (when free-living birds are normally migrating south), LD 12:12 in spring (during molt), and LD 16:8 in summer. Both body mass and use of torpor were highest in autumn, suggesting that torpor is not reserved for immediate energy crises at this time, but may be important in maximizing energy savings and thus minimizing the time required for premigratory fattening. In spring, body mass was lowest; use of torpor, however, was significantly lower than in autumn, suggesting that torpor is used primarily for "energy emergencies" at this time of year. In summer, body mass was intermediate and use of torpor was also significantly lower than in autumn. Mass-specific rates of oxygen consumption during both normothermia and torpor were inversely related to body mass when data from all seasons were combined; large fat stores may contribute to lower metabolic rates by providing additional insulation, as well as by decreasing the proportion of highly metabolically active tissue in the body. Low fat stores also coincide with the molt, which itself may result in higher metabolic rates. Although the propensity for using torpor has a strong seasonal component that appears to reflect different energetic circumstances during such activities as migration and molt, Rufous Hummingbirds retain the ability to enter nocturnal torpor at all times of year, thus improving their chances of survival year-round. Submitted 14 May 1992, accepted 12 November 1992. MIGRATORY HUMMINGBIRDS living in cool climates face potentially extreme threats to energy balance. Like other small homeotherms, they have high thermoregulatory costs resulting from high surface-to-volume ratios that increase rates of heat loss to the environment. Like other hummingbirds, they incur the additional cost of hovering, the most energetically demanding mode of flight. Unlike the many species of hummingbirds that are year-round residents in lowlatitude habitats, however, the relatively few migratory species have an additional energetic requirement-they need to accumulate large fat stores to fuel long-distance flight. Nocturnal torpor, during which energy expenditure is greatly reduced, is an important means by which hummingbirds offset large daytime energy expenditures and maintain energy balance. All species of hummingbirds that have been studied show this physiological ad' Present address: Department of Biology, Swarthmore College, Swarthmore, Pennsylvania 19081, USA. aptation. Most studies, however, have focused on instantaneous features of torpor (e.g. comparisons between rates of metabolism during steady-state torpor and steady-state normothermia), or on the effects of torpor on total nighttime energy balance (Hiebert 1990). Little consideration has been given to the fact that hummingbirds, particularly species residing at least part of the year in temperate zones, engage in activities that place very different energetic demands on the animal at different times of year. Therefore, one might expect there to be corresponding seasonal changes in the use of torpor. Yet, with the exception of Carpenter's (1974) study of the Andean Hillstar (Oreotrochilus estella), there have been no systematic comparisons of seasonal changes in the use of torpor. The seasonality of torpor has never been studied in a migratory species. The Rufous Hummingbird (Selasphorus rufus) is one of the most highly migratory species of hummingbirds. It breeds at high latitudes, as far north as Alaska, but winters in Mexico. Yearly round-trip migratory flights may exceed 6,000 km (Phillips 1975, Calder 1987). Because of their

Effect of heating nest boxes on egg laying in the blue tit (Parus caeruleus)

Abstract: ABsTRAcr.-Nest boxes of Blue Tits (Parus caeruleus) were heated from the time that nests were completed and lined (a few days before the first egg appeared) until several days after the completion of the clutch. Night-light candles placed underneath the box increased the temperature of the air in the nest box by an average of 6?C. The calculated energy savings for an average Blue Tit roosting one night in a heated nest was 0.768 Kcal, which is estimated to be equivalent to 35% of the cost of producing an egg. The percentage of nests that showed an interruption in the laying sequence was significantly lower in heated nests than in control nests. Minimum ambient temperature four and five days before these interruptions occurred was a significant factor in explaining their frequency, indicating that this is a critical period in egg production. In addition, five of six interruptions in heated nests occurred after a night when the candle was extinguished by wind, suggesting that unpredicted low temperatures on the night before laying also may affect egg laying. Received 6 January 1992, accepted 29 July 1992.

Variation in Black Bib of the Eurasian Siskin (Carduelis spinus) and Its Role as a Reliable Badge of Dominance

Abstract: Rohwer (1975, 1982) proposed that the variation and extent of color patches in the plumage of wintering birds could work as badges of social status. The major advantage of these signals would be that individuals of unequal status competing for limited resources would not need to risk accidental injury or waste energy assessing the relative fighting ability of potential opponents (Rohwer 1982). The status-signalling hypothesis has been tested in several species with variable plumage (reviewed by Whitfield 1987; see also Amat 1986, Watt 1986a, b, Fugle and Rothstein 1987, Moller 1987a, b,1989, Jackson et al. 1988). These studies have, however, produced contradictory results. For plumage differences to act as true badges of dominance, they should correlate within and not just between sex and age classes. This has been demonstrated in only a few species (Great Tit [Parus major], Jarvi and Bakken 1984; Yellow Warbler [Dendroica petechia], Studd and Robertson 1985; House Sparrow [Passer domesticus], Meller 1987a; Whitfield 1987; see however Ritchison 1985, Poysa 1988, Wilson 1992). The Eurasian Siskin (Carduelis spinus) shows great variability in the extent of blackish plumage in the bib (Newton 1972). This chin patch, as in House Sparrows (Moller 1987a), is present only in males, which are dominant over females. Dominance, however, is unaffected by age (Senar 1985). This lack of a relationship between age and dominance, and the absence of the badge in females simplifies analysis of the significance of the chin patch in status signalling. Other features in the Eurasian Siskin plumage also could be used for dominance signalling. For instance, yellow wing stripes have been found to work as a badge of status in its American counterpart, the Pine Siskin (Carduelis pinus; Balph and Balph unpubl. paper); they could have an important role. However, since wings are displayed in only 25% of the agonistic displays used by the Eurasian Siskin (Senar 1990), the chin is always visible, and most of the encounters between unfamiliar birds in wild flocks are between males (i.e. the badged individuals; Senar et al. 1990b), we restricted this analysis to the black bib. We describe variation in the size of the chin patch in male Eurasian Siskins and test (both in captivity and in the field) whether this variation is related to dominance status. Methods.-Plumage variability and dominance relations in the field were studied in a suburban area of Barcelona (NE Spain) during the 1990-1991 winter. Birds were trapped at baited feeders using platform traps and clap nets, and were marked with numbered aluminium bands. Trapping was carried out at least twice weekly, but the food was available continually so that Eurasian Siskins used the area heavily. For each male siskin we recorded, whenever possible, age and the maximum length and breadth of the badge. Badge size was measured by tilting the bird's head back in line with the body. Following the procedure of Moller (1987a), we determined the relationship between badge area, length (L, mm) and breadth (B, mm) from 12 museum skins. Thus, badge area (A, mm) was calculated as:

Phylogeographic patterns in mitochondrial dna of the ostrich (struthio camelus)

Abstract: We assayed restriction-site differences in mitochondrial DNA (mtDNA) within and among populations of the Ostrich (Struthio camelus) throughout much of its African distribution. Little genetic diversity was evident among samples drawn from localities throughout southern Africa (S.c. australis), while deep divisions in the mtDNA gene tree exist between representatives of the eastern (S.c. molybdophanes and S.c. massaicus) and northern African subspecies (S.c. camelus). The low mtDNA variability within australis and the presence of widespread mtDNA genotypes in this subspecies suggest considerable his- torical interconnectedness among populations, either through gene flow and/or recent col- onization from smaller source populations. The strong phylogeographic structuring evident in eastern and northern Africa aligns with the currently accepted subspecies designations. Data indicate that the Ethiopian system of the Great Rift Valley has been effective in disrupting east-west gene flow between molybdophanes and camelus, while ecological differences and behavioral/reproductive cues have contributed to maintaining the genetic and phenotypic discreteness of molybdophanes and massaicus in east Africa. Although contemporary Ostrich populations are effectively divided into southern and northern populations by a belt of Brachystegia woodland, arid-corridor links in the recent evolutionary past appear to have allowed for periodic contact between australis and massaicus populations. Consequently, the development of subspecific differences between these two taxa has occurred within the context of shallow evolutionary separation. Received 28 July 1992, accepted 25 November 1992. THE OSTRICH (Struthio camelus) is currently re- garded as comprising four extant subspecies separated by fairly marked phenotypic differ- ences; a fifth, S.c. syriacus, whose range once reportedly extended into Arabia, is now con- sidered extinct (Brown et al. 1982). As presently understood, the species' natural range is re- stricted to the African continent, generally south of the Sahara. This distribution is disrupted by a belt of Brachystegia ("miombo") woodland in south-central Africa (Hamilton 1982) that effec- tively divides the Ostrich into northern and southern populations with the former incor- porating S.c. camelus, S.c. molybdophanes and S. c. rnassaicus, while S.c. australis is confined to

Nest-site characteristics and nest predation in harris' sparrows and white-crowned sparrows in the northwest territories, canada

Abstract: ABssAcr.-I examined the relationship of nest-site and nest-patch characteristics to nest success in ground-nesting Harris' Sparrows (Zonotrichia querula) and Gambel's White-crowned Sparrows (Z. leucophrys gambelii) in the forest-tundra ecotone of the Northwest Territories, Canada. I found 34% of all Harris' Sparrow nests depredated, primarily by arctic ground squirrels (Spermophilus parryii), while no White-crowned Sparrow nests were disturbed by predators. White-crowned Sparrow nests appeared to be less susceptible to predation than Harris' Sparrow nests because the former were placed in areas with more shrubs and ground cover, and denser vegetation, than were Harris' Sparrow nests. Comparison of successful and depredated Harris' Sparrow nests supported the idea that interspecific differences in rates of nest predation were due to differences in concealment rather than to density-dependent nest predation. Successful Harris' Sparrow nests were placed in areas with more shrub cover and more dense vegetation within 5 m of the nest than were depredated nests. Orientation of the nest entrance did not differ between Harris' and White-crowned sparrow nests, nor between successful and depredated Harris' Sparrow nests. However, nest entrances of both species were nonrandomly oriented, with mean orientation vectors 1350 to 170? from prevailing storms. Reasons for the tendency of Harris' Sparrows to select sites where chances of predation are relatively high are unclear, but could be related to a lack of suitable nest

Structure, sequence and evolution of song elements in wild Australian Zebra finches

Abstract: --Songs from 402 Zebra Finches (Taeniopygia guttata castanotis) were sampled in order to describe the structure of the song phrase and the relationship of its elements to the call repertoire. The song of wild birds was also compared to that of 47 domesticated Zebra Finches from two European laboratories in order to examine the effects of domestication on song structure. The stereotyped phrase, which is the repetitive unit of the song, had a mean number of 6.75 elements and a mean duration of 0.86 s in wild birds. Elements were sung in sequence that defined three parts to the phrase--a start, a middle and an end. Fourteen types of elements were identified of which four were sung by the vast majority of males; three of these \"primary\" elements were \"borrowed\" unmodified from the call repertoire, and formed the start and end sections of the phrase. \"Secondary\" elements, which were less frequently represented across males, constituted the middle of the phrase and appeared to be modified versions of the Distance-call Element, the loudest element in the phrase. I tentatively conclude that Zebra Finch song may have evolved from the calls associated with flight intention and take-off. Domestication has led to changes in element morphology, frequency of occurrence, and rate of singing (elements/s), but not in number of elements per phrase. Received 9 March 1992, accepted 30 November 1992. ALTHOUGH THE SONG of domesticated Zebra Finches (Taeniopygia guttata castanotis) has become a classical subject for laboratory-based studies of the development (Immelmann 1969, Slater et al. 1988, Williams 1990), control (Nottebohm et al. 1990), and function (Clayton 1990a, b, Clayton and PrOve 1989) of behavior, few studies have investigated the structural organization of the song itself, and little information about song of the species in the wild has been published. In order to make sense of the laboratory-based discoveries that detail the specifications and constraints on the mechanisms for song learning and its perception in the Zebra Finch, it is necessary, as a first step, to make a detailed descriptive study of the acoustic structure of the song itself and its relationship with other acoustic signals emitted by the species. Cynx (1990) found that the elements or syllables-the smallest tracings on the sonagram that are temporally distinct from neighboring elements (Eales 1985)--are the functional units of song production in domesticated Zebra Finches. Consequently, they are the most basic unit of analysis in this study. Each male has, on average, seven different elements that he sings in a set order and together they constitute the phrase (\"song-unit,\" Price 1979; \"motif,\" B•hnet 1990; \"song,\" Cynx et al. 1990), which is repeated one or more times to form the song (\"bout,\" Price 1979; \"strophe,\" B•hner 1983, 1990). The first phrase of the song is preceded by several identical notes, the Introductory Elements, some of which are incorporated into the phrase pattern itself. Macrostructural features of song (number of elements per phrase, number of phrases per song, elements sung per second, and number of Introductory Elements per song) have been studied and found to differ: (1) between those songs sung in premating courtship and those undirected songs sung in noncourtship contexts (Sossinka and B•hner 1980, Bischof et al. 1981); and (2) between undirected songs of domesticated and wild birds (Slater and Clayton 1991). By contrast, there have been no studies of microstructural aspects of the song (namely, the song elements themselves, their acoustic structure and sequential organization within the phrase) in either domesticated or wild birds of the Australian (T. g. castanotis) or Timor (T. g. guttata) subspecies. Thus, my aim is to describe the structural features of song in wild Australian Zebra Finches and to draw contrasts between two focal colonies some 1,700 km apart in order to examine stereotypy in microstructure. Songs of wild birds will be compared with those of domesticated birds from Europe in order to determine what aspects of song change under domestication. Variation in

Anatomical Adaptations to Sperm Competition in Smith's Longspurs and Other Polygynandrous Passerines

Abstract: -I compared the reproductive anatomy of the polygynandrous Smith's Longspur (Calcarius pictus) with two other polygynandrous passerines (Dunnock [Prunella modularis] and Alpine Accentor [P. collaris]) and with a wide range of socially monogamous species. All three polygynandrous species were found to have enlarged testes and cloacal protuberances (i.e. the site of sperm storage) compared to species with other mating systems. Testes lengths in polygynandrous species averaged 44% longer and cloacal protuberances 213% greater in volume than expected for the body sizes of these species. Testes mass in Smith's Longspurs comprised 4.2% of adult body mass or more than twice (2.0%) that found in the congeneric and monogamous Lapland Longspur (C. lapponicus). Smith's Longspurs also had larger cloacal protuberances, larger seminal glomera and higher sperm stores, suggesting a greater overall rate of sperm production than in Lapland Longspurs. In contrast, females of polygynandrous species did not show any consistent differences in the pattern of sperm storage due to increased sperm production by males, although this needs to be evaluated more thoroughly. The enlarged male reproductive organs of Smith's Longspurs and other polygynandrous species appear to have evolved as a consequence of sperm competition, whereby large sperm reserves function to insure paternity through diluting or displacing the ejaculates of rival males. Received 26 December 1991, accepted 25 November 1992. SPERM COMPETITION results whenever females mate with more than one male during the span of a single breeding attempt (Parker 1970). Although multimale mating may be advantageous to females in some situations (e.g. Smith 1988, M0ller 1988a), it can also reduce a partner's paternity (e.g. Gibbs et al. 1990). To counter female infidelity and increase the probability of paternity, males have evolved several elaborate counter measures. For example, males in some species continually guard and defend their mates from the advances of other males during the period when eggs are fertilizable (Beecher and Beecher 1979, Birkhead 1979). If extrapair copulations occur, then pair males may reduce their subsequent parental investment to avoid wasting energy or resources on raising another male's offspring (Trivers 1972, Burke et al. 1989). Sometimes female infidelity cannot be prevented because of ecological constraints, but males may nonetheless increase paternity confidence through frequent copulations that dilute or displace rival ejaculates (McKinney et al. 1984, Birkhead et al. 1987). Indeed, inter' Present address. specific comparisons of primates (Harcourt et al. 1981, Harvey and Harcourt 1984), birds (Cartar 1985, M0ller 1991) and mammals (Kenagy and Trombulak 1986, Brownell and Ralls 1986) have shown that nonmonogamous animals have relatively larger testes than monogamous species. Since larger testes produce more and larger ejaculates (M0ller 1988b), an increase in testes size has been interpreted as an adaptation to sperm competition (Harcourt et al. 1981, M0ller 1988b, 1991). Smith's Longspurs (Calcarius pictus) are unusual among passerine birds in that females regularly pair and copulate with more than one male for a single clutch of eggs at the same time that males pair and copulate with several females (Briskie 1992). In a color-banded population near Churchill, Manitoba, 76.2% of 21 females observed mated with two males, 9.5% with three males, and only 14.3% with a single male (Briskie 1992, 1993). Of 27 males observed in the same population, 63.0% mated with two females, 7.4% with three females, and 29.6% with a single female. This combination of polyandry and polygyny is termed polygynandry and has been reported in only two other passerines to date (Dunnock, Prunella modularis [Davies 1985]