Showing papers in "The Auk in 1981"

The role of nutrient reserves in mallard reproduction

Abstract: ABSTP, ACT.--Mallard (Arias platyrhynchos) populations breeding in temperate North America obtain a significant part of the energy and lipid requirements of reproduction at sites occupied prior to arrival on the breeding grounds. Protein for egg formation, however, is obtained principally from the diet during the nesting period. Both sexes arrive heavy and fat in North Dakota but experience substantial weight loss and lipid depletion during the nesting cycle. Weight loss is most pronounced among females and averages 25% from prelaying to late incubation. Body weights of both sexes are positively correlated with carcass lipid content. The paired male draws upon lipids early in the nesting season when an activity center is being established and defended and when females are preparing to nest. The female's lipid reserves are utilized primarily during laying and early incubation. The significance of lipid reserves diminishes as the nesting season progresses, and females do not acquire substantial lipid stores prior to renesting when the initial clutch is destroyed. The magnitude of lipid reserves carried in female carcasses is positively correlated with clutch size from mid-April to early June. Protein transfer for egg formation from flight and leg muscle and body organs can account for only a small part of the protein requirement for the clutch. By utilizing lipid reserves to meet energy requirements, the female can acquire sufficient protein from the diet to produce a large initial clutch even when foods are relatively scarce, whereas the renesting female must rely entirely upon food resources available at the breeding site for its nutrient and energy requirements. Received 3 January 1980, accepted 18 July 1980.

Rarefaction, Relative Abundance, and Diversity of Avian Communities

Abstract: --The common practice of expressing community structure in terms of indices of diversity and evenness involves a serious loss of information. Differences attributable to the accumulation of species with increasing area are ignored, differences in the density of individuals are often masked by other factors, and many combinations of species richness and relative abundance can produce the same value of the index. As an alternative we suggest (1) comparing species richness by standardizing samples either to equal numbers of individuals or to the number of individuals expected on equal-sized plots, and (2) expressing the relative abundance of species as a graph of their relative abundances arranged in a decreasing array. We present an analysis of bird census data based on the proposed methods, and we include comparisons with applications of four indices commonly used in ecology, the Shannon-Weaver index of diversity, the J' evenness index, the inverse of Simpson's measure of concentration, and Hill's evenness index. For 37 Breeding Bird Censuses taken in various terrestrial habitats across the United States and Canada, the proposed methods reveal some very general relationships about the organization of bird communities in different habitats. Equal-sized areas of mature deciduous forest and secondgrowth habitats may be equally species rich (14-24 species with •> 1 breeding territory per 6 ha); the density of individuals (territorial pairs) is generally higher in deciduous forest habitats, and the relative abundance of bird species shows more dominance (less evenness) in the deciduous forest. Mixed coniferous-deciduous forests and dense young deciduous forests have fewer species than mature eastern deciduous forests or second-growth abitats (9-16 and 7-10 species per 6 ha, respectively), although the density of individuals is approximately equal to that in second-growth habitats. Coniferous forests are species-poor (5-8 per 6 ha), and the density of territorial pairs is low (8-12 per 6 ha compared with 40-70 in deciduous forests). Although the proposed methods require assumptions that need to be evaluated carefully, we are optimistic that they will have other useful applications in the analysis of arian communities. Received 8 October 1980, accepted 15 April 1981. A large literature has developed in ecology presenting descriptive analyses of biotic assemblages (Dennis et al. 1979, Patil and Taille 1979). Although one should not infer mechanisms of community regulation from such studies (Pielou 1975), certain patterns recur in vertebrate communities in different habitats (Palmgren 1930, Udvardy 1957, MacArthur and MacArthur 1961, Williams 1964, MacArthur 1964, Karr and Roth 1971, Wiens 1973, Willson 1974), climates (Bock and Lepthien 1974, Rotenberry 1978), seasons (Rotenberry et al. 1979), and geographic areas (Pianka 1966, Recher 1969, Karr 1971, Tramer 1974, Cody 1975, Short 1979). One methodological problem with much of this literature and with community ecology generally since the early 1960's is the expression of community structure in terms of indices of diversity and evenness. Indices such as H' [-5; p/log Pi] (Shannon and Weaver 1949, Margalef 1958) and J' [H'/log s] (Pielou 1966a) confound important parameters that should be defined as precisely as possible and examined separately before communities are compared. These are (1) the number of species (species richness), (2) their relative abundance (evenness), (3) the number of individuals or territorial pairs, and (4) the area sampled. To combine any of these variables into a single statistic assures that the relative effects of the contributing parameters cannot be determined. The same value of the index can result from various com785 The Auk 98: 785-800. October 1981 786 JAMES AND RATHBUN [Auk, Vol. 98 binations of values of the parameters (Pielou 1975). Here, we recommend that data be standardized to either equal numbers of individuals (in this case, territorial pairs) or equal-sized areas before comparisons are attempted. We propose that rarefaction and relative abundance curves be used as an alternative to diversity indices. In addition to clarifying components of biological interest, these methods avoid many of the mathematical deficiencies of the application of indices. We will examine the community structure of a large set of breeding bird censuses on the basis of the traditional methods and then present four graphic displays of the results of rarefactions (Figs. 1-3) and relative abundance curves (Fig. 4).

The Ecology of Seabird Feeding Flocks in Alaska

Abstract: --Seabirds commonly gather into mixed-species flocks to feed on fish schools and other concentrations of prey. We group Alaskan and Washington seabird feeding flocks into three types on the bases of flock size and longevity and the nature of the food source. Small, short-lived flocks over tightly clumped prey are called Type I; larger (5,000+ individuals), longer-lasting flocks over less tightly clumped and less reactive prey are called Type II; Type III flocks form where zooplankton and other organisms are concentrated by downwelling. Birds participating in the flocks are assigned to four functional groups (some species fit into two groups): catalysts (larids and shearwaters) are highly visible birds that other birds watch and follow to food sources; divers (alcids, loons, cormorants) exploit the food sources underwater by pursuit diving; kleptoparasites (jaegers and gulls) steal food from other flock members; and suppressors (shearwaters and cormorants) interfere behaviorally with the feeding of other flock members by reducing the effective prey availability. Most flocks occurred within a few kilometers of shore. Type I flocks on the Washington coast averaged larger, lasted longer, and contained more species than Alaskan Type I flocks. The Washington and Alaska flocks contained about the same number of locally breeding species, but the Washington flocks also contained several migrant species that breed elsewhere in North America. Both contained shearwaters, migrants from the southern hemisphere, but the shearwaters were much more important in the Alaskan flocks. Black-legged Kittiwakes and shearwaters (catalysts) initiated most Alaskan flocks and were important in the development of flocks initiated by other birds. Once a flock was initiated, it grew until the food source became unavailable or until the local pool of prospective flock members was exhausted. The divers were able to discriminate from considerable distances between kittiwakes feeding on single fish and kittiwakes feeding on fish schools and approached only the latter. The various species tended to occupy characteristic positions within Type I flocks. Gulls and kittiwakes were central, and the various divers took peripheral positions. Kleptoparasitism by jaegers did not appear to influence Type I flock organization. Shearwaters, the most important suppressors, sometimes pursuit-plunged into fish schools and euphausiid shoals in such numbers that the prey concentrations were drastically reduced, scattered, or driven downward in seconds, and other birds were then unable to feed. Type II flocks were divisible into two groups, one consisting largely of kittiwakes and shearwaters and feeding on capelin, and the other dominated by shearwaters and feeding on pelagic crustaceans. Kleptoparasitism by Pomafine Jaegers in the capelin-based Type II flocks was frequent and differed from the kleptoparasitism of solitary birds in that the jaegers preferentially attacked birds carrying fish in their bills. Suppression appeared unimportant in capelin-based Type II flocks but probably kept alcids and gulls from joining the crustacean-based flocks. In some island groups Type III flocks occurred daily. They were less regular in structure and composition than Type I or Type II flocks. Kleptoparasitism by gulls and kittiwakes tended to keep puffins and other alcids on the edges of the flocks. The alcids' underwater approaches to the fish schools from the sides may have tended to keep the schools compact and near the surface. It has been hypothesized that the 437 The Auk 98: 437-456. July 1981 438 HOFFMAN, HEINEMANN, AND WIENS [Auk, Vol. 98 antipredator function of schooling by baitfish involves predator satiation and the difficulty of locating schools. Schooling does not function as. a deterrent to aerial predators in the same way that it does to swimming ones, however. Either birds are less important as predators, or schooling confers a different advantage in escaping aerial predation. Apparently, fish schools can escape rather quickly from bird flocks by descending away from the surface out of visual contact. Received 8 January 1980, accepted 12 February 1981. FISH-EATING and other seabirds in most of the world's oceans exploit fish schools and other clumped food sources in multispecies flocks. These flocks often include several species that feed differently (Gould 1971, Scott 1973, Sealy 1973) but sometimes in a complementary manner. If indeed the birds use complementary tactics when feeding together, the assemblages may be tightly interacting, coevolved systems. We studied the arian communities of the temperate and subarctic northeast Pacific Ocean to discern how intense, consistent, and obligatory such feeding interactions are. We surveyed the geographic and hydrographic distributions of flocks in our study areas and characterized them by structure, species composition, and food

Changes in Diet and Body Composition of Canada Geese before Spring Migration

Abstract: Changes in diet and body composition of Giant Canada Geese (Branta canadensis maxima) were studied before geese initiated spring migration in early April. During the period of hyperphagia in March, body weight of female and male geese increased 36% and 26%, respec- tively, above average winter weights. Body weights of paired geese averaged 0.34 kg (females) and 0.27 kg (males) more than those of geese without mates before the weight gain period. Some unmated geese did not gain weight, and others gained less weight than paired geese. Geese shifted from a winter diet of corn (Zea mays) to a diversity of food items in spring. Corn remained the primary source of carbohydrate, and bluegrass (Poa pratensis) provided protein for geese. Weight gain of females was composed of 61% lipid, 10% protein, and 21% water, whereas weight gained by males was 47% lipid, 13% protein, and 35% water. Initial weight gains were predominantly protein (and accompanying water), probably required for gut enlargement. Most of the later body weight gain was due to lipid storage. Increase in size of breast and leg muscles at the end of March was largely due to lipid storage and a shift of protein from other body tissues. Lipid and protein storage was adequate to explain energy and nutrient requirements for body maintenance after arrival on the breeding grounds, egg laying, and territorial defense. Females may have to obtain minerals (and possibly additional protein) for egg formation from food sources on the breeding grounds. Lipid reserves of male Giant Canada Geese indicate an ability to sustain energetic costs during nesting equal to those of the female (apart from egg laying) and are greater than reserves of other species of geese and subspecies of Canada Geese investigated to date. Received 22 April 1980, accepted 21 August 1980. THE importance of lipid and protein reserves for reproduction by geese has been the subject of much recent discussion (Ankney 1977; Raveling and Lumsden 1977; Ankney and Macinnes 1978; Raveling 1978a, 1979a, b). Increases in body weight of females in spring of 41-53% of winter weight have been documented for Todd's Canada Goose (Branta canadensis interior, Hanson 1962a), Ross' Goose (Chen rossii, Ryder 1967), Lesser Snow Goose (Chen caerulescens caerulescens; Ankney 1977, Ankney and Macinnes 1978), and the Cackling Goose (B.c. minima, Raveling 1979a). These reserves provide the necessary energy for migration and reproduction and are critical in affecting clutch size. The evolutionary and functional significance of these weight gains was discussed in the papers cited above (see also Barry 1962, Ryder 1970). Few data exist on the process of acquisition of maximum body weights by geese during spring, however, and most previous studies used qualitative mea- sures or indirect indices of body composition of free-living geese (Hanson 1962a, Ryder 1970, Ankney 1977, Ankney and Macinnes 1978, Wypkema and Ankney 1979). Recently, body components were quantified and energetic strategies discussed for Common Eiders (Somateria mollissima, Korschgen 1977) and Cackling Geese (Raveling 1979a, b). The purpose of this study was to use similar methods to measure quantitatively the changes in body constituents and skeletal muscles undergone by adult Giant Canada Geese (B.c. maxima, Hanson 1965). We related these changes to food habits, social status, and timing of spring migration in order to understand better the behavior attendant to and the factors controlling the attainment of the annual reproductive state.

Male and Female Parental Roles in the Western Gull under Different Environmental Conditions

Abstract: This is the publisher's version, also available electronically from http://www.jstor.org/stable/4086120?seq=1#page_scan_tab_contents.

Estimation of distance of singing conspecifics by the carolina wren

Abstract: Measurements of the propagation of sound in a forest have shown that signal degradation is unavoidable but to some degree predictable. Carolina Wrens (Thryothorus ludovici- anus) have a song structure suited for the estimation of distance by a comparison of the relative degradation of the components of the signal. Playback experiments using song recorded at two distances from a singing wren demonstrated that wrens can use cues other than the absolute attentuation of the sound for the estimation of the distance of the singer. The wrens responded to the near-sounding song by attack and to the far-sounding song by countersinging. The ability of the wrens to use the distance information in the song serves the same purpose as the recognition of familiar neighbors: conservation of time and energy used in territorial defense. Received 26 November 1979, accepted 22 August 1980. SEVERAL recent studies have investigated the effects of the acoustics of the en- vironment in constraining the structure of the songs used for long-distance com- munication in passerine birds. Passage through the environment degrades a song by adding amplitude fluctuations and reverberations and selectively attenuating the higher frequencies. Measurements of the propagation of sound in a forest have shown that signal degradation is unavoidable but to some degree predictable (Morton 1970, 1975; Chappuis 1971; Marten and Marler 1977; Marten et al. 1977; Richards 1978; Wiley and Richards 1978; Richards and Wiley 1980). The primary concern of most researchers has been to discover those characteristics of the structure of bird song adapted for transmitting information (primarily species and individual identity) over the greatest distance. In this study I demonstrate another adaptation of birds to song degradation: the use of the predictability of the degradation present in received signals for estimation of the distance of a conspecific signaler by the Car- olina Wren (Thryothorus ludovicianus). It seems likely that individuals of many avian species are not spaced far enough apart to place strong constraints on the structure of their signals for long-range communication. Though the territory of a breeding bird may be 100 m in diameter, the bird moves around the territory while singing, frequently changing the spacing between itself and its neighbors. To discriminate between an invader inside the territory and a neighbor or other bird outside without wasting energy in a physical interaction, an individual would do well to attend to the features in the received signal that are correlated with the distance of the signaler. The overall attenuation of the received signal, however, is probably not the best cue for the distance of the source, because changes in weather would strongly affect atmospheric absorption and scattering from microclimatic heterogeneities (Wiley and Richards 1978). Much more reliable ranging would result from comparing separate features of the received signal, either different frequency bands or different periodicities of intensity in any one band.

Interhabitat Movements by Sanderlings in Relation to Foraging Profitability and the Tidal Cycle

Abstract: --Sanderlings (Calidris alba) wintering near Bodega Bay, California move between outer coast sandy beaches and nearby harbor sandflats on a regular tidal schedule. Birds forage on outer beaches at high and mid-level tides, switching to the protected sandflats as the tide recedes; Sanderling density fluctuations measured along transects were complementary in these two habitats. The habitat time budget of the local Sanderling population varied between days with different tidal regimes, averaging 45% of daylight hours spent on beaches during November 1976. Some Sanderlings defended territories on the beaches, while others foraged in flocks; both groups moved to the lagoon tidal flats at low tide. The density of Sanderling prey in the two habitats changed through the tidal cycle in foraging sites used by Sanderlings. On harbor sandflats, energy density increased sharply with falling tide level. On outer beaches, energy density was highest at middle and upper tidal levels, decreasing at low and at very high tides. These results suggest hat Sanderlings switch feeding sites on a tidal schedule to maximize foraging efficiency. We offer a simple graphical model based on tide-related changes in foraging efficiency to explain the shifts in habitat use. Sanderling behavior under seasonally varying prey conditions and behavioral comparisons of territorial and nonterritorial birds are consistent with the model. Received 16 April 1980, accepted 29 July 1980. \"There are birds everywhere, but not always.\"---Edward Howe Forbush (1921) SHOREBIRD populations wintering in coastal areas exploit a habitat mosaic dominated by the tidal cycle. Numerous studies document shorebirds' choices of foraging habitats (see papers in Pitelka 1979 and references therein). Furthermore, within habitats shorebirds respond to spatial variations in prey density and the relative profitability of using different foraging sites (Goss-Custard 1970, 1979; Goss-Custard et al. 1977; Myers et al. 1979a). Few studies, however, address the temporal effects of tides directly. This is unfortunate because of the clear importance of tides for wader feeding (Ehlert 1964, Heppleston 1971, Prater 1972, Burger et al. 1977). In this paper we examine movements by Sanderlings (Calidris alba) in response to the strong and complex tidal cycle at Bodega Bay, California. More specifically, we consider the proportion of the day spent by local Sanderlings on sandy beaches and harbor sandflats and their timing of movement between these habitats. We then develop a simple model based on changing profitabilities of foraging that summarizes the patterns of movement. Finally, we explore two predictions based on changes in the model's parameters.

Growth and energetics of chicks of the sooty tern (sterna fuscata) and common tern (s. hirundo)

Abstract: We measured the energy budgets of chicks of the Common Tern (Sterna hitundo) on Great Gull Island, New York and of the Sooty Tern (S. fuscata) on the Dry Tortugas, Florida. The respiratory energy requirement was determined by measuring oxygen consumption in a closed system. We calculated the growth energy requirement from the lipid and protein contents of a series of chicks spanning the range between hatching and fledging. Young Common Terns grow about twice as rapidly as young Sooty Terns. In most respects, their development follows a similar course, but energy budgets calculated for the two species differed in several ways. (1) Maintenance metabolism was lower in the Sooty Tern owing to its warm environment. (2) Sooty Terns allocated more of their energy intake to lipid accumulation from an earlier age. (3) In the Sooty Tern, the allocation of energy to growth initially was high, but its absolute amount decreased steadily throughout the growth period. In the Common Tern, both growth and maintenance energy al- locations increased rapidly during the first half of the development period. (4) In Sooty Tern chicks energy metabolism approached its maximum rate (135 kJ/day) by the end of the first third of the development period, after which it leveled off. In the Common Tern, energy metabolism increased from about one-quarter of its maximum during the first 5 days after hatching to its maximum of 200 kJ/day during the third week of the postnatal development period. Although these observations support the hypothesis that slow growth in pelagic seabirds is selected to reduce the energy requirement of the chick, our energy budgets also suggest that a doubling of the growth rate by the Sooty Tern would increase the maximum energy requirement of the chick by only 20% and the total feeding requirement of the adult by only 5%. Moreover, the levels of water in muscles suggest that the Sooty Tern develops mature function earlier than does the Common Tern, which in itself might be sufficient to account for the slower growth of the

Effects of Social Facilitation and Observational Learning on Feeding Behavior of the Red-Winged Blackbird (Agelaius phoeniceus)

Abstract: -In the presence of food-deprived and therefore rapidly feeding Red-winged Blackbirds (Agelaius phoeniceus), pairs of nondeprived conspecifics increased their own food consumption and spillage. The effect of social facilitation appeared amplified when both pairs of birds were food-deprived. Blackbirds also showed clear differential preferences for novel foods based on observations of male conspecifics consuming and spilling novel food. Social facilitation of feeding and observational learning of differential food preferences for novel foods may help to explain the Red-winged Blackbird's tendency to locate and exploit (i.e. damage) crops during short periods when the crops are especially vulnerable. Received 30 January 1981, accepted 21 April 1981. SOCIALLY facilitated behavior such as flocking may protect birds from predators (Conner et al. 1975, Clayton 1979, Lazarus 1979) and contribute to reproductive synchrony (Roell 1978). Social facilitation may also lead to a more complete exploitation of food resources by birds through more rapid selection of new foods (Davies 1976, Traemer and Kemp 1979) or through increased food consumption (Rubenstein et al. 1977, Feare and Inglis 1979). Consumption is influenced by the feeding rates of neighboring birds in a flock, regardless of their sex, or, sometimes, their species (Fairchild et al. 1977). In addition, consumption is discriminative for most species, i.e. individuals forage selelctively and tend to choose foods that other birds in the flock are choosing (e.g. Murton 1971, Williamson and Grey 1975). Social facilitation of food selection among members of a flock may have deleterious agricultural consequences. For example, foraging based on observational learning may encourage the selective crop damage that is often produced by gregarious pests, such as Red-winged Blackbirds (Agelaius phoeniceus). Here, we report two experiments that demonstrate that: (1) Red-winged Blackbirds will increase their feeding activity in the presence of feeding conspecifics; and (2) Red-winged Blackbirds differentially select some foods as a result of observing the behaviors of other individuals. EXPERIMENT 1, SOCIAL FACILITATION OF FEEDING

Extramarital and Pair Copulations in the Cattle Egret

Abstract: --The copulatory behavior of the Cattle Egret (Bubulcus ibis) was observed in a heronry in central Japan. In 38 of 147 extramarital copulation (EC) attempts with seven females, the males seemed to succeed in ejaculation. There were relatively few complete ECs prior to egg laying, because females responded aggressively to approaching males and because the mates of the females stayed in the territories for 78.8% of the time and protected the females. After egg laying, the aggressiveness of females against approaching males decreased and their mates spent more time outside the territories, resulting in an increase in the occurrence of complete ECs. Fighting males that were approaching a female exhibited a dominance hierarchy. The most dominant male stayed in the territory for the longest time and copulated most intensively with his mate and other neighboring females. Extramarital copulations are likely to occur in colonial herons, but mate-guarding by the male and aggression by the female mate enhance the probability that copulations will be performed only between members of the pair during the fertilizable period of the female. Thus, the monogamous pair bond is maintained. Received 24 April 1980, accepted 3 September 1980. IN recent years there has been a growing interest in extramarital or promiscuous copulations (\"rape\"; McKinney 1965, MacRoberts 1973, Barash 1977, Bailey 1978, Wishart 1978, Beecher and Beecher 1979, Gladstone 1979, Mineau and Cooke 1979). In herons, there is little quantitative information on the frequency of extramarital copulations (ECs), although qualitative observations note its occurrence (Meanley 1955, Blaker 1969, Lancaster 1970, Wiese 1976, Gladstone 1979). Inoue (in prep.) found that ECs comprised 23% of 121 complete copulations in the Little Egret ( E gretta garzetta ). We observed many ECs during a breeding study of the Cattle Egret (Bubulcus ibis). Here we describe the behavior accompanying both pair copulations and ECs, analyze quantitative data on the temporal variation in the frequency of ECs, and consider underlying causal factors. STUDY AREA AND METHODS Our study was conducted in a heronry located 15 km north of Tsu City, Mie Prefecture, central Japan (34ø50'N, 136ø35'E). The altitude is 20 m above sea level. The heronry has been established for many years on a small island (50 x 300 m) in the Ishigaki Pond (ca. 400 m in diameter), which is mostly surrounded by rice fields. The island is mainly covered with a thick forest of the Japanese black pine (Pinus thunbergii), the crowns and branches of which furnish suitable nesting sites for herons. During our study, the heronry consisted of more than 1,000 birds of five ardeid species: Little Egrets, Blackcrowned Night Herons (Nycticorax nycticorax), Intermediate Egrets (Egretta intermedia), Cattle Egrets, and Great Egrets (Casmerodius albus), in order of decreasing abundance. All of our observations were made from a blind on a 3.6-m-high scaffold at the southern edge of the heronry. Copulatory behavior was observed with the unaided eye or with a binocular telescope (9 x 35) as necessary. Observations were carried out for 34 days, from 10 May to 20 June 1978, amounting to a total of 455.5 h; the longest observation period was from 0330 to 2000. Because B. ibis lacks sexual dimorphism, the individuals that laid eggs or were repeatedly mounted by their mates were considered females. No \"reverse mounts\" were observed in two pairs (369.1 observation-h) in which the sexes were determined by egg laying. All members of the 10 pairs that we observed were individually recognizable by idiosyncracies in the bill, leg, lore, plume, and so on. Seven pairs 134 The Auk 98: 134-144. January 1981 January 1981] Copulations in the Cattle Egret 135

Nest-Site Habitat Selected by Woodland Hawks in the Central Appalachians

Abstract: --We quantitatively describe the nest-site habitat selected by Broad-winged Hawks (Buteo platypterus), Red-shouldered Hawks (B. lineatus), Red-tailed Hawks (B. jamaicensis), and Cooper's Hawks (Accipiter cooperii), emphasizing differences among species and between each species and the surrounding forest habitat. We subjected 53 nest sites and 100 randomly selected sites to an intensive habitat analysis based upon the James and Shugart (1970) techniques. White oak (Quercus alba) was the most common nest tree. Distance to water, percentage nest height, distance to the nearest forest opening, basal area, and dbh of the nest tree were important discriminating variables between the hawk species. Compared with the random sample of the available forest area, Broad-winged Hawks nested closer to water and to forest openings. Redshouldered Hawks consistently nested near water and in large trees in stands of mature forests. Red-tailed Hawks nested higher in trees than did the other species, on or near the top of ridges, and far from water and forest openings. Cooper's Hawks nested proportionally higher in trees than did Broad-winged and Red-shouldered hawks and were associated with mature forest with a well-developed understory and ground cover layer. A discriminant function analysis revealed that each species appears to select rather specific nesting areas, as characterized by the proximity of the site to various physiographic features and the structure of the nest tree. Received 21 April 1980, accepted 23 September 1980. FEW studies of raptors have attempted to describe nest-site habitat use in forested areas quantitatively (Dietzen 1978, Hennessy 1978, Howell et al. 1978, Keran 1978, Bednarz 1979). Most habitat descriptions for raptors have been qualitative, with little comparison of sympatric species. In this study we examined the habitat characteristics associated with the nest sites of four sympatric falconiformes, Broadwinged Hawks (Buteo platypterus), Red-shouldered Hawks (B. lineatus), Red-tailed Hawks (B. jamaicensis), and Cooper's Hawks (Accipiter cooperii). Our objectives were to (1) describe habitat characteristics at the nest sites of each species quantitatively, (2) compare differences in nest sites among the species, and (3) compare nest-site habitat for each species with available nesting habitat.

Golden-Winged Warblers and Blue-Winged Warblers: The Relative Success of a Habitat Specialist and a Generalist

Abstract: ABSTP, ACT.--Evidence of the decline of Golden-winged Warblers (Vermivora chrysoptera) in Tompkins County, New York is presented, which adds to other examples of decline elsewhere. This decline is temporally correlated with an increase in Blue-winged Warblers (V. pinus). In Tompkins County, the Golden-winged Warbler nests only in the shrub stage of successional habitat on large patches of abandoned farmland. Blue-winged Warblers use later stages of succession as well as the early stages. A small decrease in the amount of recently abandoned farmland in Tompkins County with a larger increase in the amount of land in later stages of succession helps explain the decrease in Golden-winged Warblers and the increase in Blue-winged Warblers. The large magnitude of decline in Golden-winged Warblers, however, suggests that there may also be some negative biological interaction with the recently arrived and increasingly abundant Blue-winged Warbler. Received 19 May 1980, accepted 21 August 1980.

Colony Site Dynamics and Habitat Use in Atlantic Coast Seabirds

Abstract: -Seabird colony sizes and movements were documented in the DelMarVa coastal region in 1976-1977 and in New Jersey in 1978-1979. Most colonies were found on marsh and dredge deposition islands and on barrier island beaches. For the "traditionally" beach-nesting Herring Gull, Common Tern, and Black Skimmer, larger, more stable colonies were found on barrier beaches than on marsh islands. In marsh habitats, rates of colony-site change of marshnesting Forster's Tern and Laughing Gulls were similar to those of the former beach nesters. Several adaptations have evolved in marsh specialists to cope with a high risk of reproductive failure due to flooding, but both Herring Gulls and Common Terns also appear to be very adaptable in nesting under various habitat conditions. New colonies and those abandoned between years may be pioneering attempts by younger or inexperienced birds, because they are often smaller than persistent colonies, although patterns differ among areas and habitats. Colony-site dynamics are complex and result from many selective factors including competition, predation, physical changes in site structure, and flooding. The invasion of Herring Gulls into marshes along the mid-Atlantic coast has had an impact on new colony-site choice by associated seabirds. Calculating colony-site turnover rates allows for comparisons among species, habitats, and regions and may give useful insights into habitat quality and change and alternative nesting strategies. Received 10 November 1980, accepted 20 February 1981. COLLECTIVELY, colonially nesting seabirds (here referring to gulls, terns, and Black Skimmers, Rynchops niger) nest in a variety of habitats along the North and mid-Atlantic coast, including beaches and dunes, salt marshes, dredge deposition islands, rocks, etc. (Bent 1921, Stone 1937, Erwin 1979a). Some species are habitat specialists. Forster's Terns (Sterna forsteri) and Laughing Gulls (Larus atricilla), for instance, nest nearly exclusively in salt marshes in the mid-Atlantic coastal region (Montevecchi 1978, Storey 1978, Erwin and Korschgen 1979). Others such as Common Terns (Sterna hirundo) and Herring Gulls (Larus argentatus) nest in several different habitat types ranging from marshes to rocky islands (Burger 1977, Burger and Lesser 1978, Erwin 1980). Recently, many North and mid-Atlantic coast colonies of Herring Gulls, Common Terns, and Black Skimmers have shifted from their traditional (Bent 1921, Stone 1937) outer beach-dune habitats to salt marshes and bay islands, due largely to human disturbances along beaches (Buckley and Buckley 1977, in press; Burger 1977; Burger and Lesser 1978; Erwin 1980). Recent coastal surveys (Erwin 1979a, Erwin and Korschgen 1979, Parnell and Soots 1980, Buckley and Buckley in press) showed that in the states with the greatest coastal zone development, the use of marsh and dredge deposition islands by traditional "beach nesters" is highest. Major changes in breeding habitat use patterns pose a number of ecological and evolutionary challenges to the individual organism. More specifically for nesting seabirds, the major factors affecting the relative fitness of the individual in different 550 The Auk 98: 550-561. July 1981 This content downloaded from 157.55.39.180 on Tue, 27 Sep 2016 05:45:12 UTC All use subject to http://about.jstor.org/terms July 1981] Seabird Colony-site Dynamics 55 1 habitats include the risk of flooding of eggs or young (Greenhalgh 1974, Montevecchi 1978, Burger 1979a, Burger and Lesser 1979), the physical stability of sand, marsh, and rocky substrates (McNicholl 1975, Southern 1977), predation (Buckley and Buckley 1972, Burger 1979b, Burger and Lesser 1978), and competition for nest sites (Crowell and Crowell 1946; Nisbet 1971, 1973; Burger and Shisler 1978; Erwin 1980). For ground-nesting seabirds in disturbed areas, the shift from use of open, dry duneand beach-sand substrates to the more vegetated wet marshes of lower elevation represents an abrupt change; both Common Terns and Herring Gulls, however, have demonstrated sufficient plasticity to make at least one important adjustment-nest building behavior (Burger 1979a). Other species, such as Black Skimmers, may not be quite as "plastic," as they are nearly exclusively sand nesters. In addition to the change in the physical regime of the nesting site, the biotic environment might also change with more intense competitive and predatory interactions occurring as the amount of occupiable habitat becomes limiting. Large, aggressive Herring Gulls usurp nest sites by breeding earlier than most other species and also prey on the young of other species (Hatch 1970, Burger 1977, Burger and Lesser 1978). Both Common Terns (Burger and Lesser 1978, 1979; Erwin 1980; see Nisbet 1973 and Drury 1973, 1974 for historical review) and Laughing Gulls (Nisbet 1971; Burger 1977, 197 9a; Burger and Shisler 1978) have been shown to be adversely affected by the presence of nesting Herring Gulls. Ultimately, the ability of each species to cope with these changes should be reflected in the reproductive output of the individuals affected. Low reproductive success in seabirds is often associated with declining colony size or abandonment of colony sites (Crowell and Crowell 1946, Morris and Hunter 1976, Burger unpubl. data). Because these habitat shifts have occurred mostly in the past 30-50 yr (Stone 1937, Buckley and Buckley 1977, Burger 1977, Erwin 1980), we would expect selection still to be acting rather strongly (a nonequilibrium condition). We propose here to compare the dynamics of colony-site use and colony sizes among five seabird species in New Jersey, a region of intense coastal development, with that on the Delaware-Maryland-Virginia (hereafter DelMarVa) coast, an area comprised largely of undisturbed barrier islands (Erwin 1980). In New Jersey, virtually all nesting of the five species is on salt marsh islands or dredge deposition islands, while in Virginia Herring Gulls, Common Terns, and Black Skimmers still nest primarily on barrier island beaches and dunes under relatively pristine conditions (Erwin 1980). Given the above scenario, we pose the following questions: (1) Are beach-dune colonies of the "traditional beach" nesters any different in size or stability from year to year than those colonies in marshes or on dredge islands? (2) Are colonies of the marsh-adapted species, i.e. Forster's Tern and Laughing Gull, more consistent in site use from year to year than the marsh "invaders?" Presumably, the latter species have not had sufficient time to acquire fine-tuned adaptations and, hence, are possibly inferior in judging high quality sites in marshes. (3) Do new colonies or colonies abandoned between years differ in any way from those that persist? (4) How does the presence of the competitively dominant and predatory Herring Gull influence the colony-site choice of other species? We respond to these questions by examining comprehensive census data collected since 1976. This content downloaded from 157.55.39.180 on Tue, 27 Sep 2016 05:45:12 UTC All use subject to http://about.jstor.org/terms 552 ERWIN, GALLI, AND BURGER [Auk, Vol. 98

Hind Limb Morphology, Phylogeny, and Classification of the Piciformes

Abstract: ABSTR•1⁄2T.--The phylogenetic relationships of the order Piciformes were studied by a cladistic analysis of variations in the hind limb muscles. Forty-four species in 30 genera were dissected. The two main questions addressed are (1) is the order Piciformes monophyletic, and (2) what are the phylogenetic relationships within the order? Monophyly of the order is corroborated by the presence of a complex synapomorphic specialization of the foot, the combination of zygodactyly and the Type 6 deep plantar tendon arrangement of Gadow. These traditional characters, now seen as derived states, are augmented by a derived condition of M. flexor hallucis longus. Arguments refuting an alternative hypothesis are presented. The phylogenetic hypothesis is presented in a cladogram. There are two main lineages, one including the Bucconidae and Galbulidae, the second the remaining families. The second lineage is further subdivided dichotomously, one lineage including the Capitonidae and Ramphastidae, and the second the Indicatoridae and Picidae.

Geographical Variation and Functions of Song Types in Warblers (Parulidae)

Abstract: --Chestnut-sided Warblers (Dendroica pensylvanica) and Blue-winged Warblers (Vermivora pinus) sing different song types in different contexts. Local dialects exist in the \"Unaccented Ending\" songs (often termed the \"Type II\" song for the Blue-winged Warbler), but the \"Accented Ending\" songs (or the \"Type I\" songs) vary only slightly throughout the breeding ranges of the two species. The degree of geographical variation in song types suggests that intrasexual selection has promoted dialects in Unaccented Ending (Type II) songs, while intersexual selection may have played a greater role in maintaining the stereotypy of Accented Ending (Type I) songs. Received 6 January 1981, accepted 21 April 1981. MOST male songbirds learn to sing (Thorpe 1958, Marler 1970, Kroodsma 1977), and limited dispersal from the site of learning (not necessarily the site of hatching) usually leads to micro-geographical variation in songs (Thielcke 1969, Baptista 1975). But whether the selective forces leading to these song dialects (where neighboring males have songs more similar to one another than to more distant yet local males) are primarily intrasexual or intersexual remains unclear. Local dialects in bird song could be maintained because shared song types are more effective in malemale countersinging over territorial rights; alternatively, the female, through mate choice, could maintain the homogeneity of song patterns within a confined geographical area (Marler and Tamura 1964; Nottebohm 1969; Thielcke 1969; Kroodsma 1974, 1979; Lemon 1975; Payne and Payne 1977; Baker and Mewaldt 1978). Difficulty in clarifying this problem arises because most well-studied songbirds have multi-purpose songs that are used in a variety of contexts. On the other hand, many wood warblers (Parulidae) use different song types in different contexts (Ficken and Ficken 1962, 1965, 1967; Morse 1966, 1967, 1970; Lein 1972, 1978) and are therefore ideal subjects for studying the functions of geographical variation. In this paper I assess and discuss the relative degrees of geographical variation in the different song types of the Blue-winged Warbler (Vermivora pinus) and the Chestnut-sided Warbler (Dendroica pensylvanica).

Foraging Behavior of the Red-Cockaded Woodpecker in South Carolina

Abstract: Foraging Red-cockaded Woodpeckers (Picoides borealis) selected live pines (96% use; 71% availability) over hardwoods (1% use; 25% availability). Use of recently dead pines (3%) was the largest departure from use of live pines. Mast was rarely consumed, although abundant at times. Live pine stems greater than 23 cm in diameter at breast height represented only 19% of the available pines but received 65% of the use. The sexes exhibited strong divergence in foraging behavior. Most important was the partitioning of foraging sites on live pines. Males foraged on dead and live limbs of the crown and midtrunk 54% of the time and females only 4%. On the lower trunk, females foraged 38% of the time and males only 3%. On the midtrunk, females foraged 29% and males 12%. On the trunk-in-crown, females foraged 28% and males 32 %. Mean foraging height of males was 14.1 m and that of females 8.7 rn (P < 0.001). The sexes used tree sizes, tree types, and methods for capturing prey with similar frequencies. Within each sex, there were between-season differences in use of foraging sites and in methods used at each site. Received 9 July 1980, accepted 5 January 1981.

Seasonal Variation in the Foraging Behavior of Some Migratory Western Wood Warblers

Abstract: -I observed the foraging behavior of four warbler species (Dendroica petechia, Oporornis tolmiei, Geothlypis trichas, and Wilsonia pusilla) in the summer in Wyoming and in the winter in Nayarit, Mexico. Of six variables (absolute foraging height, relative foraging height, vegetation density, horizontal foraging position, feeding method, and foraging substrate) believed to be potentially important in distinguishing the warbler species ecologically, the two foragingheight variables provided the greatest separation of the four species in both summer and winter. An analysis of the behavioral similarity of each species from summer to winter revealed that feeding method was the least changed behavior and that absolute foraging height involved the greatest behavioral flexibility. The behaviors that are most flexible are possibly the least well tied to the birds' morphology and are also the ones that have been shown by other workers to reveal the effects of competitors through "niche shifts." Therefore, ecological relationships among coexisting species (in terms of overlaps or positions in niche space) may never be fully derivable from morphological information alone. Received 6 March 1980, accepted 24 March 1981. ECOLOGICAL studies of Nearctic migrants on their breeding grounds are relatively common, but such studies on their wintering grounds are less common (but see Eaton 1953, Schwartz 1964, Willis 1966, Lack and Lack 1972, Leck 1972, Tramer 1974, Rappole 1975, Chipley 1976, Karr 1976, Mills 1976, Post 1978, Wilz and Giampa 1978, or some of the more recent studies included in Keast and Morton 1980). Comparative studies that deal with the ecology of migratory species on both their breeding and wintering grounds are rarer still (but see Root 1967, Baker and Baker 1973, Lack 1976, Bennett 1980, Rabenold 1980). Only through such comparative studies will we begin to understand the extent to which the morphology of a species represents a compromise among behaviors that vary seasonally (Fretwell 1972). In this paper I quantify the foraging behavior of four species of migratory wood warblers (Yellow Warbler, Dendroica petechia; MacGillivray's Warbler, Oporornis tolmiei; Common Yellowthroat, Geothlypis trichas; and Wilson's Warbler, Wilsonia pusilla) that can be found syntopically during both the breeding and nonbreeding seasons in western North America to determine (1) whether several potential mechanisms of ecological isolation change seasonally, and (2) which aspect of foraging behavior shows the grestest seasonal flexibility. STUDY SITES AND METHODS I collected foraging data on the four warbler species from 20 May-20 June 1975 within 4 ha of willow (Salix) habitat adjacent to the Jackson Hole Biological Research Station, Grand Teton National Park Wyoming (43?52'N, 1 10'34'W). Willows were the only large plants growing in the study area, and the open areas between them were filled with grasses and sedges. A foliage-height profile, which depicts the porportion of vegetation at different heights, is given in Fig. 1. Winter foraging data were collected from 15 January to 15 February 1975 and 1976 in second growth Present address: Department of Zoology, University of Montana, Missoula, Montana 59812. 765 The Auk 98: 765-777. October 1981 This content downloaded from 150.131.112.212 on Wed, 16 Oct 2013 20:33:09 PM All use subject to JSTOR Terms and Conditions 766 RICHARD L. HUTTO [Auk, Vol. 98

The Phylogenetic Relationships of the Piciformes (Class Aves)

Abstract: ABST•CT.--The phylogenetic relationships of the avian order Piciformes were studied using a cladistic analysis of the skeletal morphology. We hypothesize that the piciforms constitute a monophyletic group on the basis of possessing a unique flexor tendon pattern in the hindlimb, a M. flexor hallucis longus with three heads of origin, zygodactyly, and a well-developed sehnenhalter on the outer (IV) trochlea of the tarsometatarsus. Two major lineages are defined by osteological characters, one (the Galbulae) consisting of the Galbulidae and Bucconidae, and the other (the Pici) comprising the remaining four families. Within the Pici, two lineages are discerned: the Ramphastoidea, consisting of the Ramphastidae and the Capitonidae, and the Picoidea, which includes the Picidae and Indicatoridae. The systematic position of the fossil families Zygodactylidae and Primobucconidae are interpreted within the framework of the phylogenetic hypothesis for the Recent families. Received 24 September 1980, accepted 15 January 1981.

Genic Heterozygosity in the White-Crowned Sparrow: A Potential Index to Boundaries between Subspecies

Abstract: ABST•CT.--Estimates of the average heterozygosity, •, based on the genic variability at 44 loci, are presented for eight Pacific coastal populations of the White-crowned Sparrow (Zonotrichia leucophrys). Four of the localities sampled span the geographic distribution of Z. I. nuttalli, at least one represents Z. l. pugetensis, and the others fall along a north-south transect of the zone of intergradation between these two subspecies. Estimates of • are highest in the zone of intergradation and decrease significantly with distance north or south from the presumptive midpoint of the contact zone. This decrease closely approximates an exponential decay curve that peaks in the contact zone, decreases exponentially both northward and southward, and asymptotically approaches a value equal to the average heterozygosity of passerine birds. Received 15 September 1980, accepted 7 April 1981.

Nest Spacing, Reproductive Success, and Behavior of the Great Black-Backed Gull (Larus marinus)

Abstract: --A study of the relationship of nest spacing, reproductive success, and behavior of the Great Black-backed Gull (Larus marinus) was conducted during the 1979 breeding season. Egg production and hatching success were similar on territories in high and low density areas, but gulls in high density areas fledged significantly fewer chicks than those in low density areas. Adults breeding in high density areas engaged in significantly more bouts of agonistic interactions and chick-oriented vocalizations than pairs in low density areas, although there were no significant differences between the two groups in the frequency of long calls, choking bouts, or chick feedings. The results of this investigation are related to a model proposed by Hunt and Hunt (1976) that predicts that, in the absence of interspecific predation, larger territories may confer a reproductive advantage on some larids due to a decrease in conspecific interference. Received 11 April 1980, accepted 18 July 1980. NEST spacing within seabird colonies is a direct function of the size of the breeding territories defended around the nest sites. Breeding territory size may be considered an adaptation responsive to selection pressures such as predation, competition for nesting habitat, and conspecific social and aggressive characteristics. As nest spacing exhibits the natural variability inherent in any evolutionary adaptation, it may be hypothesized, for a given set of environmental conditions, that reproductive success would be related to some optimal nesting density or territory size in colonial species. This hypothesis has been examined in the family Laridae with conflicting results. Nesting density was not found to be related to chick survival in Glaucous-winged Gulls (Larus glaucescens, Vermeer 1963), Black-headed Gulls (L. ridibundus, Patterson 1965), Ring-billed Gulls (L. delawarensis, Dexheimer and Southern 1974), or Western Gulls (L. occidentalis, Hunt and Hunt 1975). Although Fordham (1964) demonstrated a positive correlation between nearest-neighbor distance and egg losses in the Dominican Gull (L. dominicanus), he was unable to establish a relationship between nearest-neighbor distance and chick survival in a later study (Fordham 1970). In contrast, Parsons (1971) observed that Herring Gulls (L. argentatus) exhibited maximum breeding success at median nesting densities, and Hunt and Hunt (1976) were able to show a positive correlation between the size of the breeding territory and chick survival in Glaucous-winged Gulls. Although the variability in these reported results may be due to methodological, environmental, and/or speciesspecific differences, it is clear that additional data (both reproductive and behavioral) will be necessary to clarify this problem. The objectives of the present study were to: (1) investigate the relationship between nest spacing and reproductive success in a colony of Great Black-backed Gulls (L. marinus), and (2) examine behavioral factors that might have been related to the reproductive success of pairs breeding in high versus low density areas.