bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Foraging Ecology of Peruvian Seabirds
Authors: Duffy David Cameron 
Published: September 2019

Abstract
Most feeding by seabirds in the Peruvian Coastal Current, an upwelling of high productivity off the west coast of South America, takes place in groups. The major prey is an anchovy (Engraulis ringens), which occurs in large shoals and is exploited mainly by three species: the Peruvian Booby (Sula variegata), Peruvian Brown Pelican (Pelecanus occidentalis thagus), and Guanay Cormorant (Phalacrocorax bougainvillii). Other foraging situations have different species' compositions, and these appear to be related to the size, depth, and duration of availability of prey. Dominance interactions between species may be important in structuring flocks that are scavenging or feeding on plankton swarms. Interspecific piracy seems unimportant in flocks foraging on fish shoals. Certain species usually arrive first at new feeding situations. These species may be used as guides by other species or merely may be faster and thus reach food sources first. Studies of foraging of seabirds should be a valuable addition to the study of the distribution of birds at sea.
Nest-Site Selection by the Red-Tailed Tropicbird
Authors: Clark L. , Ricklefs R. E. , Schreiber R. W. 
Published: September 2019

Abstract
Red-tailed Tropicbirds (Phaethon rubricauda) nest under shrubs in loosely associated groups on Christmas Island, Central Pacific Ocean. Aggressive interactions among adults at nest sites are high; yet, large areas of superficially similar habitat contain no tropicbird nests at all. We compared physiognomic features of nest sites with those of two sets of randomly generated "nest sites" by discriminant function analysis. Of those variables measured, the number of stems within a nest space and the amount of peripheral cover influenced the tropicbirds' choice of nest sites. Differences among localities existed. Areas where tropicbirds nested had shrubs with few stems and more peripheral cover. Preferred nest sites were rare in areas other than those in which tropicbirds were nesting already. This study demonstrates the utility of the discriminant function technique in quantifying nest-site selection and nest-site availability when the appropriate null data sets are used.
Feeding Habitats of Nesting Wading Birds: Spatial Use and Social Influences
Authors: Erwin R. Michael 
Published: September 2019

Abstract
In an effort to relate social interactions to feeding-habitat use, I observed six species of wading birds near a major colony site in coastal North Carolina. Three spatial scales of habitat use were considered: the general orientation to and from the colony (coarsest level), the habitat "patch," and (at the finest level) the microhabitat. Departure-arrival directions of Great Egrets (Casmerodius albus), Snowy Egrets (Egretta thula), Cattle Egrets (Bubulcus ibis), Little Blue Herons (Egretta caerulea), Tricolored Herons (Egretta tricolor), and Glossy Ibises (Plegadis falcinellus) were monitored at the colony site to document coarse patterns of feeding-habitat use. Added to these data were observations made at five different wetland sites to monitor between-habitat and within-habitat patterns for the five aquatic-feeding species.
The results indicated a broad and variable use of feeding habitat over time. At the coarsest scale (i.e. orientation at the colony), diffuse patterns, influenced little by either inter- or intraspecific social interaction, were found for all species. At the next level (habitat "patch"), only one of five wetland sites was relatively consistent in attracting feeding birds, and its use increased from May to June. Few groups were seen at four of the five sites. At the one "attractive" site, the within-habitat patterns again were spatially variable over time, except for those of the abundant Snowy Egret, whose microhabitat preference was fairly consistent. Glossy Ibises and Snowy Egrets frequently formed mixed-species groups, Little Blue Herons were the least social, and Great Egrets and Tricolored Herons generally occurred in groups of less than 10 birds but rarely in groups larger than 30. The close association between Snowy Egrets and Glossy Ibises appeared to be based on a "beater-follower" relationship, wherein the probing, nonvisually feeding ibises make prey more available to the followers. In the study area, local enhancement appeared to play a more important role than did any "information-sharing" at the colony.
Occurrence and Timing of Second Clutches in Common Terns
Authors: Wiggins David A. , Morris Ralph D. , Nisbet I. C. T. , Custer Thomas W. 
Published: September 2019

Abstract
Eighteen pairs of Common Terns (Sterna hirundo) at three different colonies laid second clutches while still feeding young from their first broods. Seven clutches were laid before the chicks from the first brood fledged, and 11 were laid after the chicks from the first brood fledged. In each case, parents alternately fed chicks from the first brood and incubated the second clutch. Sixteen of the 18 clutches disappeared, were addled, or were deserted. Young hatched from the two other second clutches, but all chicks died or disappeared 2-4 days after hatching. We suggest that a second clutch, laid before chicks from the first brood fledged, probably results from a physiological miscue associated with chick loss from the first brood and stimulated by an unusual surplus of food. Conversely, when laid after chicks from the first brood fledge, a second clutch might function as insurance, permitting a pair to raise young late in the season if chicks from the first brood are lost. In either case, parents must partition care between eggs and chicks from the second clutch and fledged chicks from the first brood. Accordingly, the successful fledging of chicks from two broods in a single season is unlikely unless exceptionally favorable conditions occur.
Components of Variance in Measurements of Nestling European Starlings (Sturnus vulgaris) in Southeastern Pennsylvania
Authors: Ricklefs Robert E. 
Published: September 2019

Abstract
I report the results of experiments designed to distinguish factors affecting within-population variability in measurements of nestling European Starlings (Sturnus vulgaris). Individuals were switched among pairs of nests at the beginning of the incubation period and at the beginning of the nestling period. Variables were analyzed in a replicated (nested), three-way factorial analysis of variance to distinguish the contributions of factors associated with (1) the genotype of the embryo or composition of the egg, (2) the incubation period, and (3) the nestling period. In addition, I analyzed the correlations among growth variables within the sample as a whole and among main effects in the experimental design to search for patterns of genotypic and phenotypic interrelationship. I also related growth variables of nestlings to the size and composition of sibling eggs and to the length of the incubation period. The present experiment did not reveal any genetic or egg-quality component to within-population variation in rate of mass increase and mass asymptote achieved, length of the tarsus of fully grown nestlings, or rates of growth of the wing and outer primary feather. Similarly, the nest in which the individual was incubated had no effect on postnatal growth. The nest in which the individual was reared significantly contributed between 19 and 29% of the sums of squares in rate of mass increase, length of the tarsus, rate of increase in length of the wing, and the maximum length of the sheathed portion of the outer primary feather. Rearing nest did not have a significant effect on the mass plateau of the chick. These results, particularly the absence of some effects, are difficult to interpret, because a large proportion of the variation in several variables occurred between pairs of switched nests. These differences undoubtedly included some of the variation that might have been attributable to effects within experiments. Growth variables were weakly correlated over the entire sample, revealing little pattern of variation in postnatal growth. Over certain of the effects in the experimental design, however, particular groups of variables were strongly correlated, indicating interrelated responses of some of the growth parameters to environmental and, perhaps, genetic factors. The size of the egg had a small effect only on the mass plateau and the length of the tarsus of the chick. The composition of a sibling egg influenced only the maximum length of the sheath of the outer primary feather. The present study was somewhat weakened by small sample size and an inexplicable between-experiment effect that reduced its power to distinguish among effects of interest. The experimental design has the potential, however, to disentangle many classes of factors associated with genotype and parental care that contribute to within-population variation in phenotypic measurements.
Avian Anatomical Specimens: A Geographic Analysis of Needs
Authors: Jenkinson Marion Anne , Wood D. Scott 
Published: September 2019

Abstract
The anatomical inventories of Wood et al. (1982a, b) indicated that nearly one-third of the world's bird species are not represented by skeletal specimens or spirit specimens. Additionally, long series of anatomical specimens, necessary for many kinds of studies, exist for only a very few species. To encourage collectors to fill in gaps in anatomical holdings, we divided the world into 60 geographic areas, developed avifaunal lists for these, and indicated what species in each area are most critically needed as anatomical specimens. The details are given by Wood and Jenkinson (1984). Various analyses indicate that collecting efforts are most needed in the following areas: Colombia, Venezuela, Bolivia-Peru-Ecuador, Brazil-Paraguay-Uruguay, Africa (except north Africa), the Indian subcontinent, Burma, New Guinea, Madagascar, Seychelles, and the islands north of Australia (except Borneo). Although collecting efforts are especially important in those areas, specimens are needed from all sites to provide series from throughout each species' range. Curators and collectors should make new or renewed efforts to increase anatomical holdings through a variety of approaches to specimen acquisition and preparation.
Brood Parasitism in a Host Generalist, the Shiny Cowbird: II. Host Selection
Authors: Mason Paul 
Published: September 2019

Abstract
Host selection by brood parasitic Shiny Cowbirds (Molothrus bonariensis) was studied at two sites in Buenos Aires Province, Argentina. The eggs of the parasite are either spotted or immaculate, so host selection was studied with respect to egg type as well as to site. Immaculate eggs were rare at both sites. Cowbirds in this region prefer to parasitize nests of birds larger than themselves. This preference contrasts with that of almost all other brood parasites, and even that of Shiny Cowbirds in other parts of the species' range. One large species, the Chlk-browed Mockingbird (Mimus saturninus) was used frequently and consistently at both sites. At least two other large species (thrushes) were used at Site I, but neither was present at Site II. Cowbirds were more specialized on large hosts at Site I: only 9% of the spotted eggs were laid in nests of small birds at Site I, whereas 35% were laid in such nests at Site II. Small species, such as the Rufous-collared Sparrow (Zonotrichia capensis), were used to a greater extent at Site II than Site I (where some of the same species were not used at all). The shift to smaller hosts is probably a response to a change in the structure of the community; large host species are relatively less abundant at Site II.
Rejecter species are large, and all were parasitized while many smaller accepter species were unmolested. Surprisingly, more immaculate eggs were laid in nests where they had little chance of successful incubation, rather than in nests of accepters. No evidence suggests that host races ("gentes") are formed. To the contrary, female cowbirds laying different egg types apparently select hosts in the same manner.
Clutch Size and Fledging Success in the Turquoise-Browed Motmot
Authors: Scott Peter E. , Martin Robert F. 
Published: September 2019

Abstract
Clutches of 4 eggs accounted for 64-73% of all clutches laid in 3 yr by a population of Turquoise-browed Motmots (Eumomota superciliosa) in Yucatán, Mexico. The consistently high frequency of 4-egg clutches was associated with only a slight advantage in fledging success relative to clutches of 3 eggs, which ranged in frequency from 11% to 33%. Differences in number of young fledged and proportion of hatchlings fledged were not statistically significant over 3 yr or in any particular year. Clutches of 4 yielded more surviving young in 2 of 3 yr, averaging 2.02 compared to 1.71 for clutches of 3. The proportion of hatchlings that fledged was higher in broods of 3 (overall = 0.67) than in broods of 4 (overall = 0.55) in 2 of 3 yr. The proportion of hatchlings fledged from clutches of 5 (0.36) was lower over 3 yr than that fledged from clutches of 4 or 3. Approximately 40% of nestling mortality in nests that escaped predation was due to starvation. Other known causes included falls from nests and parasitism by maggots.
Differences in Susceptibility to Predation during Nesting Between Pied and Black Stilts (Himantopus spp.)
Authors: Pierce Raymond J. 
Published: September 2019

Abstract
The nesting success of the Pied Stilt (Himantopus himantopus leucocephalus) and the endangered Black Stilt (H. novaezealandiae) was studied for three consecutive breeding seasons (1977-1979) in New Zealand. Black Stilts had a breeding success of less than 1%, compared with over 8% for Pied Stilts. Predation by feral mammals was the main cause of nest failure for both species, but the impact was greater on Black Stilts. Direct and indirect evidence (including trapping predators) suggests that these introduced ground predators kill many chicks. Several factors made Black Stilts vulnerable, particularly their nesting along stream banks that were often frequented by predators; Pied Stilts nested in swamps where predators were few. Black Stilt chicks took up to 2 weeks longer to fledge and their foraging patterns made them more vulnerable than Pied Stilt chicks. Other factors that possibly increased predation risk of Black Stilts include nesting at times of high predator activity, solitary nesting, high site fidelity, ineffective distraction displays, and lack of a disruptive camouflage pattern in adults. Introduced ground predators probably have contributed greatly to the decline of Black Stilts. Pied Stilts have not been affected similarly, because their evolutionary past has included long exposure to ground predators.
Molt of Female Lesser Scaup Immediately Following Breeding
Authors: Austin Jane E. , Fredrickson Leigh H. 
Published: September 2019

Abstract
The chronology, pattern, and intensity of the molt following breeding in female Lesser Scaup (Aythya affinis) were studied from July through October 1981-1982 and in July 1984 in southwestern Manitoba. Nonbreeding females or females that were unsuccessful breeders began molt in mid-July, but females with broods delayed molt until August. The molt-intensity index was greatest during the flightless and postflightless periods. Molt persisted at low levels through the fall migratory period. Molt scores were most variable in the preflightless period. Molting began on the head, neck, and side and progressed to the belly, upper back, and chest; the lower back was the last area to molt. Feather replacement was most rapid in the wing and capital regions. The capital region and tail were the last areas in which molt was completed in fall-migratory scaup. Molt in postbreeding females probably is influenced by the length, timing, and success of breeding efforts. Individual and geographic differences in breeding chronology, habitat conditions, and postbreeding movements may contribute to variations in molt within a population of migratory scaup.
Generic Status of Euler's Flycatcher: A Morphological and Biochemical Study
Authors: Lanyon Wesley E. , Lanyon Scott M. 
Published: September 2019

Abstract
A concordance in the distribution of uniquely derived character states of the syrinx and of six protein coding loci confirms that euleri should be removed from the genus Empidonax and that its nearest relatives are Cnemotriccus and Aphanotriccus. A hypothesis that euleri is the sister taxon of Aphanotriccus is based on the sharing of a uniquely derived syringeal structure and two synapomorphic allozymes, and on the comparatively low genetic distance between them. A new genus, Lathrotriccus, is proposed for euleri, which differs from Aphanotriccus in its cranial morphology. The reassignment of euleri increases the desirability of obtaining anatomical specimens and tissue of griseipectus, the only remaining South American endemic in Empidonax, and of tissue of Xenotriccus, a near relative of euleri on the basis of syringeal morphology.
An Analysis of Vocal Communication in the Adult Brown Noddy (Anous stolidus)
Authors: Riska Diane E. 
Published: September 2019

Abstract
I analyzed vocal signals of marked adult Brown Noddies (Anous stolidus) throughout their nesting season in the Dry Tortugas, Florida from 1979 to 1982. The basic unit of the adult repertoire is a wide-band click, less than 4 msec duration, ranging in frequency from 200 to 3,300 Hz. I identified nine temporal arrangements of these clicks, which form the notes of the calls. These calls differ little in frequency range, but they differ in the mean frequency of the most intense sound energy band, in note duration, in the number of clicks per note, and in internote interval. These calls are used in different contexts, which sometimes overlap. Frequency, note duration, and internote interval do not differ between sexes. Mean frequency and note length varied among individuals for some calls. No tonal elements characteristic of calls of Brown Noddy nestlings remain in the adult repertoire.
Metabolism, Growth, and Activity in Adélie and Emperor Penguin Embryos
Authors: Bucher Theresa L. , Bartholomew George A. , Trivelpiece W. Z. , Volkman N. J. 
Published: September 2019

Abstract
The eggs of Adélie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) penguins are smaller than those of large species in other orders. The incubation period in Adélie Penguins was as predicted based on egg mass, but in Emperor Penguins it was 50% longer than predicted. Although penguins have been described as semialtricial using the behavioral and morphological traits in Nice's (1962) classification, total oxygen consumption during incubation was similar to that of eggs of the same masses laid by precocial species. In both penguin species prepipping oxygen consumption was at a level predicted for precocial species.
Adélie embryos grew continuously during the last two weeks of incubation, but the relative growth rate (%/day) of both wet and dry mass decreased steadily until day 32 of incubation. From day 21 to day 31 of incubation, there was no significant change in the wet mass, dry mass, or caloric content of yolk. The mass-specific caloric content of the embryos remained constant at 5.49 kcal/g dry mass. Activity of the embryo between pipping and hatching contributed importantly to measured oxygen consumption (∼10% of the total measured during incubation, ∼20% in pipped eggs from 3 days to 1 day before hatching, and ∼25% on the day of hatching).
We suggest that the limited behavioral repertoire of hatchling penguins evolved as a response to the severity of the environment into which they hatch and because of the skilled predatory behavior that they must learn before they can feed themselves.
Population Ecology of the Long-Billed Curlew (Numenius Americanus) in Western Idaho
Authors: Redmond Roland L. , Jenni Donald A. 
Published: September 2019

Abstract
In western Idaho, a breeding population of Long-billed Curlews (Numenius americanus) remained relatively stable over a 7-yr period. Productivity was monitored closely from 1977 through 1979. Clutch mortality rates did not differ significantly among years, and mean clutch survival for a 32-day nesting period (4 days egg laying and 28 days incubation) was 40% for all 3 yr combined. Females laid just one clutch (usually of 4 eggs) each season, and mean clutch size was significantly smaller in 1979 than in 1977 and 1978. Estimated fledging success ranged from 0.40 in 1977 to 0.17 in 1978 and was consistently greater for females that nested early each season. Mean annual adult survival was estimated at 85% based on resightings of color-marked individuals. Limited data for subadult survival precluded complete demographic analysis. Nevertheless, given the estimates of productivity and adult survival pooled for 3 yr, survival of subadults from fledging until first breeding as 3-year-olds needed to be only 58% to maintain the stable population size observed through 1983.
Field Metabolism and Food Consumption of Savannah Sparrows during the Breeding Season
Authors: Williams Joseph B. 
Published: September 2019

Abstract
I applied the doubly labeled water (DLW) technique to measure rates of water flux and energy expenditure of Savannah Sparrows (Passerculus sandwichensis) during two breeding seasons on Kent Island, New Brunswick, Canada. Simultaneous to DLW measurements, I constructed time-activity budgets for territorial males, monitored nest attentiveness for incubating females, and quantified frequency of nest visitation for parents feeding young. To ascertain the relationship between brood size and adult energy expenditure, I measured the energy expenditure of adults feeding 2, 4, and 6 nestlings. There was little difference in field metabolic rates (FMR) between territorial males [161.0\pm 21.7 (SD) ml CO2/h). and males that fed 4 nestlings (157.6 ± 19.7 ml CO2/h). Incubating females expired CO2 at rates lower than males during the same time period (134.4 ± 7.9 vs. $161.0 ± 21.7 ml CO2/h but similar to rates for females feeding 4 young, the normal brood size ($134.4 ± 7.9 ml CO2/h for incubating females vs. $136.5 ± 26.9 ml CO2h for females feeding young). Incubating females expended energy at a lower rate than females making 8 or more trips to the nest per hour, the average feeding rate for females late in the nestling period. For males and females together, water influx and efflux rates averaged 17.1 ± 3.2 and 17.2 ± 3.0 ml H20/day, suggesting that birds balanced water intake against water losses. Mean daily solar radiation (MDSR; W/ m2) also influenced FMR during the nestling period. The equation ml CO2/h=172.6-0.07 (MDSR) described the relationship. When brood sizes were manipulated, parents responded by altering their frequency of nest visitation; as frequency increased, so did the FMR of females but not of males. The equation ml CO2/h =98.4 + 5.3 (mean visits/h) described the relationship. Construction of a food budget indicated that, on average, territorial males consumed 21.1 g fresh arthropods per day, while incubating females ingested 17.5 g/day or 210.0 g during the 12-day incubation period. Through the 8-day nestling period, males augmented their foraging by 75%, females by 87%, to feed a brood of 4.
The Influence of Diet Quality on Clutch Size and Laying Pattern in Mallards
Authors: Eldrigde Jan L. , Krapu Gary L. 
Published: September 2019

Abstract
We measured the effect of diet quality on variation in the seasonal pattern of Mallard (Anas platyrhynchos) reproduction. Twenty wild-strain hens, consisting of 10 sibling pairs, were maintained in captivity. One sib of each pair was fed an enriched diet, and the other was fed wheat. The wheat diet resulted in reduced clutch size, egg size, laying rate, number of nesting attempts, and total eggs laid. Diet did not affect laying initiation, duration, or the seasonal pattern of change in clutch and egg size with each renest. We believe the variation and pattern observed are adaptations to a highly variable prairie environment where the probability of reproductive success decreases as the season progresses.