bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time and Energy Budgets of the Mockingbird (Mimus polyglottos) during the Breeding Season
Authors: Biedenweg Douglas W. 
Published: October 2019

Abstract
A time and energy budget of male and female Mockingbirds (Mimus polyglottos) in six phases of their breeding cycle was completed using the equivalent temperature model to predict perching metabolic rates. Recorded time-budget behaviors included perching, bipedal locomotion, flight, and the time spent in the sun and shade. Over the total study period, males and females spent an average of 92.3% and 92.8% of their active day perched, 2.4% and 1.6% in bipedal locomotion, and 5.3% and 5.6% in flight, respectively. BMR plus thermostatic requirements averaged, seasonally, 78.1% of DEEtot in males and 76.1% in females. The choice of shaded or exposed microhabitats made very little difference in energy expenditure. DEEtot varied from 96.9 kJ in males with incubating females to 113.0 kJ in males caring for fledglings, and from 75.1 kJ in incubating females to 113.2 kJ in females caring for fledglings. Unmated, pre-nest-building, and incubating birds spent significantly less energy than did birds caring for nestlings (P < 0.05) or birds caring for fledglings (P < 0.05). With the exception of the nest-building phase, when females are producing eggs, and the incubation phase, when females gain insulation from the nest, male and female DEEtot closely paralleled each other throughout the season. The large amount of predation that occurred at the study site suggests that birds may allocate time to perching to minimize the probability of predation on themselves or their offspring.
Hunting Behavior, Prey Selection, and Energetics of Snail Kites in Guyana: Consumer Choice by a Specialist
Authors: Beissinger Steven R. 
Published: October 2019

Abstract
The hunting behavior, snail size selection, and time-activity patterns of non-breeding Snail Kites (Rostrhamus sociabilis sociabilis) were studied in Guyana rice fields. Kites spent 62% of the photoperiod perching, 19% foraging, 13% in maintenance activities, and 6% flying. As the day progressed, the percentage of daylight hours spent perching increased significantly, while foraging decreased significantly. Kites successfully captured and ingested Pomacea snails in 78% of the foraging bouts observed. The mode of hunting was evenly split between coursing (50.7%) and still-hunting (49.3%). Searching and returning times were related to time of day, as significantly more coursing hunts and still-hunts occurred in mornings and late afternoons, respectively. Prey handling time was the most time-consuming component of a foraging bout. Time spent searching for prey, returning, or handling prey was not related to snail size. The size distribution of captured snails differed significantly from that of available snails; kites selected more medium snails and fewer small snails and took large snails in equal frequency to that at which large snails were available. Kites captured the same-sized snails when coursing as when still-hunting. As rice grew, kite utilization of rice fields declined, and the frequency of still-hunting decreased while course-hunting attempts increased. The daily caloric intake of kites was estimated to be 104.2 kcal, the daily energy expenditure 85.7 kcal. Results are discussed in relation to consumer choices of specialists. The most important decision a foraging Snail Kite may make is what patch to search in and how long to search before abandoning patches.
Communication with Shared Song Themes in Tufted Titmice
Authors: Schroeder Donna J. , Wiley R. Haven 
Published: October 2019

Abstract
Individual Tufted Titmice (Parus bicolor) sing 8-12 song themes. Most or all themes in an individual's repertoire are shared with neighbors, although slight but consistent differences often separate neighbors' performances of a particular theme. Birds first begin to sing recognizable themes while still juveniles on their parents' territory. Established territorial residents can modify their themes slightly from year to year to achieve a closer similarity to neighbors' themes. Neighbors matched themes during concurrent singing more often than would be expected at random. Furthermore, titmouse tended to begin singing in response to a neighbor, particularly if it could match the theme. Playbacks of recorded song also evoked matched singing in response. Playbacks of strangers' songs, recorded 3 km away, evoked a less intense response than did playbacks of neighbor's songs, but an attempt to demonstrate individual recognition of a neighbor's shared themes failed. Evidently, the advantages of coordinated singing by opponents with shared themes outweigh any advantages of individual recognition of neighbors with distinctive songs.
Brood Reduction in Black-Legged Kittiwakes
Authors: Braun Barbara M. , Hunt George L. 
Published: October 2019

Abstract
In 1978 and 1979 we studied brood reduction in Black-legged Kittiwakes (Rissa tridactyla) on St. Paul Island, Alaska. In two-egg clutches, first-laid eggs were largest; they were incubated before second eggs were laid and consequently hatched first. Chicks from first-laid eggs begged more frequently, fed more frequently, grew faster, and were more aggressive than their sibs. These sibling differences frequently facilitated the ejection of younger siblings from the nest by first-hatched young. Lower feeding and growth rates and higher aggression levels occurred in broods in which the second chicks subsequently died than in broods in which both chicks fledged. Chick loss was most frequent during inclement weather. These data are consistent with the hypothesis that brood reduction is related to the amount of food that chicks receive.
Aspects of Food Finding by Wintering Bald Eagles
Authors: Knight Susan K. , Knight Richard L. 
Published: October 2019

Abstract
We examined three aspects of food location by Bald Eagles (Haliaeetus leucocephalus) wintering along the Nooksack River, Washington. First, eagles used intra- and interspecific local enhancement to locate food. Second, the time that eagles spent aerially searching for food, as indicated by the percentage of eagles flying or soaring, was negatively correlated with relative food availability. Third, eagles often followed others when departing from or arriving at communal night roosts. Following was most frequent when all food was eliminated by flood waters, suggesting a possible food-location function of this behavior. During the flood period, adult eagles were followed more often than immatures.
The Pattern of Migration of Village Weaverbirds (Ploceus cucullatus) in Southwestern Nigeria
Authors: Adegoke A. S. 
Published: October 2019

Abstract
I investigated the migration of Village Weaverbirds (Ploceus cucullatus) in southwestern Nigeria in order to determine the sources of birds causing crop damage. I observed banded adult, juvenile, and nestling weaverbirds at their colonies, roosts, and feeding grounds. Over a 21-month period, 6 birds were recaptured at the point of ringing and another 6 at a maximum distance of 1.5 km from the point of ringing. This and other observations indicate that Village Weaverbirds do not undertake long-distance migrations and that local bird populations cause the damage to local crops. Some Village Weaverbirds roost on shrubs and grasses throughout the year, some breed and sleep in colonies in villages from January to early August and from October to early December, and some roost in tall trees near human dwellings from late December to April. The birds roosting on shrubs and grasses are more accessible than the birds roosting in tall trees, and their elimination would provide a more effective means of control than does the present method of scaring the birds from a particular area.
The Reaction of Great Tits (Parus major) to Playback of Degraded and Undegraded Songs: The Effect of Familiarity with the Stimulus Song Type
Authors: McGregor Peter K. , Krebs John R. , Ratcliffe Laurene M. 
Published: October 2019

Abstract
We played degraded and undegraded song types to territorial Great Tits. Each bird was tested with degraded and undegraded renditions of a song type in its repertoire and of a song not in its repertoire. The birds responded less strongly to degraded than to undegraded songs, and the difference was significant only if the test song was of the same type as, or similar to, one in the bird's repertoire. These results are consistent with Richards' (1981) hypothesis that degradation cues are used to judge distance and Morton's (1982) idea that degradation may be judged by comparison with a standard consisting of the bird's own rendition of the song. We also found that birds are better able to discriminate between undegraded and degraded song types if their neighbors sing the song. The results are discussed in relation to hypotheses concerning song matching and neighbor-stranger discrimination.
A Complex Call of the Black-Capped Chickadee (Parus atricapillus). I. Microgeographic Variation
Authors: Ficken Millicent S. , Weise Charles M. 
Published: October 2019

Abstract
We studied the syllabic structure of the Gargle, a complex vocalization of the Black-capped Chickadee that is often associated with agression, at three main sites in southeastern Wisconsin, at one site over an 11-yr period. Sites as close as 5.7 km showed major differences in syllables, and birds at some sites differed somewhat in the number of syllables per call. Each individual probably uses all the syllables (16-23 different ones) occurring at a particular site. The syllables occurring at the end of the vocalization were shared among different demes, while the introductory syllables were usually different. Syllables showed relatively little change with time. Dialects apparently correspond to demes in this species. The syllables are arranged in many combinations and permutations to generate a large variety of Gargle types, most of which are very rare. A few Gargle types are more common ("universals") and are usually confined to a particular site. Such a complex dialect pattern is unusual in a call.
Differences in Repertoire Size, Singing Behavior, and Associated Neuroanatomy Among Marsh Wren Populations Have a Genetic Basis
Authors: Kroodsma Donald E. , Canady Richard A. 
Published: October 2019

Abstract
Among songbirds, adult song forms usually are determined culturally during an individual's early experience. In the Marsh Wren (Cistothorus palustris), we have demonstrated that the quantity of this learned behavior (i.e. song repertoire size), its style of delivery, and the size of controlling nuclei in the forebrain have a genetic basis. Nestling males taken from New York and California and reared under standardized conditions in the laboratory still develop population-typical behavior and neuroanatomy. We do not know the developmental mechanisms responsible for these differences, but we believe that year-round residency, high densities, and polygynous mating systems are likely factors contributing to an escalation of vocal abilities in the western populations.
Hybridization, Introgression, and Morphometric Differentiation between Mallard (Anas platyrhynchos) and Grey Duck (Anas superciliosa) in Otago, New Zealand
Authors: Gillespie Grant D. 
Published: October 2019

Abstract
Small numbers of Mallard (Anas platyrhynchos) were introduced into New Zealand from Great Britain and North America over 100 years ago. Both sexes have undergone differentiation in size and plumage characters as a consequence of hybridization with the indigenous Grey Duck (A. superciliosa). Pure forms of both species, as documented by early descriptions, appear to be disappearing, particularly the Grey Duck. In Otago, the Mallard and Grey Duck are introgressively hybridizing, and the majority of intergrades are Mallard-like in appearance. Separation of Mallards, hybrid birds, and Grey Ducks was achieved using a stepwise cluster analysis of mensural characters. The observed morphometric differentiation was not continuous throughout the Otago population, and a total of 5 discontinuities (groups of morphologically similar birds) were distinguished: male Mallards, female Mallards, Grey Ducks, and 2 groups of hybrid birds. The use of bivariate scattergrams of skull length and eye-lens weight provided the most useful illustration of the distinctions among Mallard, hybrid, and Grey Duck populations. As a consequence of hybridization, two morphologically distinct hybrid populations have been produced: one resembles the Grey Duck and the other the Mallard. This situation is discussed in relation to the two hybrid forms of the Marianas Mallard (A. oustaleti).
The Mallard was so successful in newly created agricultural habitat that by 1958 this species constituted 53% of the Mallard-Grey Duck population. Prior to 1958 the observed hybrid frequency was less than 3% and the reduction in the proportion of the Grey Duck most probably was the result of habitat reduction. In 1977 the Mallard comprised 82% of the Mallard-Grey Duck population, and there was concern over the number of pure Grey Ducks remaining in Otago. By 1981-1982 levels of hybridization, based on plumage analysis, had reached 51%, and the proportion of pure Grey Ducks had dropped to 4.5%, which is below the level suggested for the maintenance of a species. In the absence of reproductive isolation or antihybridization mechanisms between these two species, the Mallard and hybrid populations represent a potential threat to the conservation of the New Zealand Grey Duck.
The Phylogeny of the Alcidae
Authors: Strauch J. G. 
Published: October 2019

Abstract
An estimate of the phylogeny of 22 extant and 1 extinct species of the Alcidae was determined from compatibility analyses of 33 cladistic characters of the skeleton, integument, and natural history. The puffins were found to be a sister-group to all other alcids. Cerorhinca was found to be a puffin. The auklets were found to be a sister-group to the remaining species. Brachyramphus was found to represent a phyletic line separate from that including the other murrelets. Cepphus was found to be a member of the phyletic line including Endomychura and Synthliboramphus. Alle was found to be a sister-group of the auks. A compatibility analysis of muscle characters of Hudson et al. (1969) yielded a phylogenetic tree in agreement with that found using my data. The relationships among Cepphus and the murrelets were found to need further study. A classification based on these results is suggested. It is recommended that the recent merging of genera by the A.O.U. (1982) be accepted, that Cyclorrhynchus be merged with Aethia, and that Pinguinus be merged with Alca.
Multiple Paternity in a Territorial Passerine: The Bobolink
Authors: Gavin Thomas A. , Bollinger Eric K. 
Published: October 2019

Abstract
Electrophoretic and behavioral evidence corroborate the conclusion that Bobolink (Dolichonyx oryzivorus) females occasionally copulate with more than one male, which results in the insemination of a single clutch of eggs by those males. In 2 of 12 families from which blood samples were obtained from the mother, the putative father, and the nestlings, at least 2 males were responsible for fertilization of the clutch. We believe this is only the second bird species in which multiple paternity has been documented conclusively in the wild. Our speculation that it may not be uncommon leads to a caution for evolutionary biologists who use apparent reproductive success in birds to address questions about fitness.
Natal Dispersal and Lek Fidelity of Sage Grouse
Authors: Dunn Peter O. , Braun Clait E. 
Published: October 2019

Abstract
Natal dispersal and lek fidelity (attendance within and between years) of Sage Grouse (Centrocercus urophasianus) were studied on Cold Spring Mountain, northwestern Colorado, from July 1981 through May 1984. Female Sage Grouse followed the typical avian pattern of dispersing farther than males. However, there was no difference between proportions of male and female yearling grouse attending the lek closest to their juvenile banding location. Fifteen percent of all individually marked juveniles (24/157 birds) were known to have attended leks as yearlings. There was no difference between yearling and adult lek attendance rates for either sex; however, females attended leks less often than males. Yearling females, but not yearling males, visited 2 or more leks more often than adults. These differences may be related to yearlings' inexperience with breeding or to a strategy to enhance reproductive success.
A Fixed-radius Point Count Method for Nonbreeding and Breeding Season Use
Authors: Hutto Richard L. , Pletschet Sandra M. , Hendricks Paul 
Published: October 2019

Abstract
We provide a detailed description of a fixed-radius point count method that carries fewer assumptions than most of the currently popular methods of estimating bird density and that can be used during both the nonbreeding and breeding seasons. The method results in three indices of bird abundance, any of which can be used to test for differences in community composition among sites, or for differences in the abundance of a given bird species among sites. These indices are (1) the mean number of detections within 25 m of the observer, (2) the frequency of detections within 25 m of the observer, and (3) the frequency of detections regardless of distance from the observer. The overall ranking of species abundances from a site is similar among the three indices, but discrepancies occur with either rare species that are highly detectable at great distances or common species that are repulsed by, or inconspicuous when near, the observer. We argue that differences in the behavior among species will preclude an accurate ranking of species by abundance through use of this or any other counting method in current use.
Daily Activity Patterns of South Polar and Brown Skuas Near Palmer Station, Antarctica
Authors: Pietz Pamela J. 
Published: October 2019

Abstract
I conducted a behavioral study of sympatrically nesting South Polar (Catharacta maccormicki) and Brown skuas (C. lonnbergi) near Palmer Station, Antarctica. A total of 4,058 bird-hours of observations was made on eight South Polar, three Brown, and one mixed-species pair during the 1979-1980 and 1980-1981 austral summers. I used subsets of these data to analyze various aspects of skua activity patterns.
South Polar Skuas exhibited maximum resting and minimum foraging activity during the twilight period around 2400. Brown Skuas appeared to rest and forage more randomly. Members of the mixed pair exhibited patterns similar to those of their respective species. Several hypotheses are suggested to account for species differences in activity patterns; most of these relate dietary differences and differential foraging abilities at low light levels.
In both species, agonistic and preening activities occurred at all hours. South Polar Skuas, however, were most often observed bathing in early afternoon and preening in afternoon and twilight. Pairing activity showed no discernible relationship with time.
Foraging bouts averaged 13 min for Brown Skuas with feeding territories and about 1 h for those without. South Polar Skuas averaged feeding trips of 2-3 h when the sea was open and over 7 h during heavy ice cover.
The timing of an individual's activity was correlated negatively with that of its mate during incubation, brooding, and postbrooding. A nonbreeding pair and breeders that had suffered nest failure showed more positive correlations. Thus, individual activity patterns were shaped by reproductive priorities as well as by feeding ecology and light levels.
Diet Selection by Yearling Northwestern Crows (Corvus caurinus) Feeding on Littleneck Clams (Venerupis japonica)
Authors: Richardson Howard , Verbeek Nicolaas A. M. 
Published: October 2019

Abstract
Yearling and adult Northwestern Crows (Corvus caurinus) used similar methods in searching for buried Japanese littleneck clams (Venerupis japonica) and therefore encountered similar proportions of different-size clams. The mean size of clams eaten by yearling birds was significantly smaller than the mean of those eaten by adults despite the similar proportions encountered. The estimated lower limit of the diet (the smallest clams eaten by the average bird) was 25.5 mm for yearlings and 29.0 mm for adults. Yearlings took more time to find and handle clams and required more drops to break them open than did adults. Consequently, yearlings achieved only one-third the rate of net energy intake of adults feeding from the same food source. However, the extended diet consumed by the yearlings yielded close to the maximum possible rate of energy intake, within the limits imposed by their inefficiency.
Roost Attendance and Aggression in Black Vultures
Authors: Rabenold Patricia Parker 
Published: October 2019

Abstract
In a 5-yr study of a partially marked population of Black Vultures (Coragyps atratus) in North Carolina, turnover among marked birds in a large winter roost averaged 34% each night. Roost attendance and areawide resighting rates differed among age classes; juveniles remained site faithful while young adults ranged far, and adults were intermediate in movement. Local breeders were more consistent in year-round attendance at roosts near their nest sites than were other marked adults using these roosts, and local breeders were likewise overrepresented on initial days at baited feeding sites. During aggressive interactions at roosts and at food, adults won over young birds and juveniles lost to older birds. Breeding adults won more fights close to their nest sites than farther away. Winners of fights at roosts were more likely to be present on subsequent evenings than were losers. The results suggest that food-finding adults, primarily local breeders, can to some extent control local roost membership by means of aggressive interactions in roosts. Successful foragers can reduce the costs of being followed and sharing food by limiting the number and identity of potential followers through aggression.
A Feeding Adaptation of the Jaw Articulation in New World Jays (Corvidae)
Authors: Zusi Richard L. 
Published: October 2019

Abstract
The jaw articulation of most endemic New World jays (Corvidae) has a condyle of the quadrate and an opposing cotyla of the lower jaw not found in other birds. They also have well-developed meatic articular facets of the quadrate and cranium. The tip of the rhamphotheca of the lower mandible is chisel shaped. These and other features constitute a functional unit, the buttress complex, that braces the partially opened lower jaw and enhances its use as a chisel. The buttress complex stabilizes the lower jaw by anchoring the jaw on the quadrate and reducing torque on the quadrate during pounding. A hypothesis of pounding with the lower mandible was confirmed by field observations of Aphelocoma coerulescens coerulescens, which stabs acorns with the lower mandible and then tears off the shell using both mandibles. This may be an unusually effective method of peeling acorns, and it differs from the techniques used by Garrulus and Pica. The origin of the complex may not be associated with acorn eating. A slight modification of the jaw articulation in Cyanolyca probably represents the evolutionary precursor of the buttress complex. The distribution of the complex in the Corvidae suggests that Cyanolyca is the sister group of other endemic New World jays. Gymnorhinus is related to the New World jays, not to Nucifraga. An example of convergent evolution is provided by Hemignathus wilsoni (Drepanidinae).