bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sex-related Differences in Habitat Use in Wintering American Kestrels
Authors: Ardia Daniel R. , Bildstein Keith L. 
Published: September 2019

AbstractWe investigated sex-related differences in habitat use in wintering American Kestrels (Falco sparverius) at two scales: within a 10 m radius and within a 100 m radius of perch sites. Female kestrels used areas containing a higher percentage of short vegetation (<0.25 m high) suitable for foraging than did males at both scales (100 m radius females 80%, males 69%; 10 m radius females 80%, males 73%). At both scales, females had more pasture (a high-quality foraging substrate) available than did males; areas within a 100 m radius of male perch sites contained more woodlot than did female perch sites. Logistic regression models indicated greater overlap between male and female habitat use on a 10 m radius scale than on a 100 m radius scale, suggesting that males may preferentially select smaller areas devoid of woody vegetation relative to what is available within 100 m radius of perch sites. Our results suggest that males may be constrained to winter in areas with lower overall foraging opportunities and possibly higher predation risk than areas used by females. Our work supports the hypothesis that males and female kestrels prefer open areas as wintering habitat.
Composition and Growth of King Eider Ducklings in Relation to Egg Size
Authors: Anderson Vanessa R. , Alisauskas Ray T. 
Published: September 2019

AbstractIn several bird species, offspring from larger eggs survive better than birds from smaller eggs, but mechanisms responsible for that pattern have not been clearly identified. Studies of waterfowl have found relationships between egg size, body composition of hatchlings, and duckling growth. Therefore, body composition and growth rate of newly hatched King Eider (Somateria spectabilis) ducklings were measured to assess if traits consistent with higher probability of survival early in duckling varied in relation to egg size. Forty-one King Eider eggs were collected in June and July 1998 from two lakes in the central Canadian Arctic, and artificially incubated, of which 34 hatched. Body composition of 15 hatchlings (<1 day old) was determined, and 19 ducklings were raised in captivity to measure growth rate. Larger eggs produced larger ducklings with absolutely more lipid and protein reserve; absolutely larger breast and leg muscles; higher functional maturity for whole body, leg, and breast muscles; and higher tarsal growth rates than ducklings from small eggs. Such patterns of hatchling composition and growth in relation to increasing egg size may improve likelihood of early survival by improving thermogenesis, reducing time spent as optimal prey size for avian predators, and as shown elsewhere, by enhancing motor performance of ducklings through improvements in foraging efficiency and predator evasion.
Importance of Native Bamboo for Understory Birds in Chilean Temperate Forests
Authors: Reid Sharon , Díaz Iván A. , Armesto Juan J. , Willson Mary F. 
Published: September 2019

AbstractIn South American temperate rainforests, five endemic understory birds (four Rhinocryptidae and one Furnariidae) are often associated with the main understory plant, the native bamboo Chusquea valdiviensis (Poaceae: Bambusoideae). We studied the effects of bamboo cover on species abundance and richness of those understory birds and explored the functions of bamboo as food resource and escape cover. In Chiloé Island (42°S), southern Chile, we selected four old-growth forest patches >100 ha and in each patch conducted bird surveys in six plots with >70% understory cover. Three plots were dominated by native bamboo and three plots had a sparse bamboo cover. Bird abundance (point counts) was significantly correlated with both total understory cover and percentage of bamboo cover but was not correlated with other kinds of understory plant cover. Bird species richness was positively correlated with bamboo cover and negatively correlated with other kinds of understory cover but unrelated to total understory cover. Leaf-gleaners Magellanic Tapaculos (Scytalopus magellanicus), Ochre-flanked Tapaculos (Eugralla paradoxa), and Des Murs's Wiretails (Sylviorthorhynchus desmursii), and the ground-gleaner Chucao Tapaculos (Scelorchilus rubecula) were more abundant in high-bamboo plots; but the ground-gleaner Black-throated Huet-huet (Pteroptochos tarnii) was recorded more times in plots with low-bamboo cover.Availability of invertebrates per unit of understory dry mass did not differ between high- and low-bamboo plots; but plant biomass was greater in high-bamboo plots, so total invertebrate abundance per plot was higher there. Ground-litter invertebrate abundance was similar in all plots. To examine escape-cover preferences, nine captured Chucao Tapaculos were released in front of two different understory scenarios (high-bamboo cover or bamboo-free understory); 88% of released birds moved into bamboo cover. We suggest that the structure of native bamboo understory is critical for the maintenance of four of those species, and retaining bamboo cover in managed stands may help minimize the effect of logging on understory birds.
Nesting Ecology of White-Winged Scoters (Melanitta Fusca Deglandi) at Redberry Lake, Saskatchewan
Authors: Traylor Joshua J. , Alisauskas Ray T. , Kehoe F. Patrick 
Published: September 2019

Abstract
Population surveys indicate a trend of declining abundance of scoters (Melanitta spp.) in North America. Little is known about changes in life-history traits that may be responsible for the recent population decline of White-winged Scoters (Melanitta fusca deglandi). Therefore, we studied nesting ecology of White-winged Scoters at Redberry Lake, Saskatchewan, during the summers of 2000–2001. We found 198 nests and examined nest-site selection by comparing habitat features of successful nests, depredated nests, and random sites. Discriminant function analysis differentiated habitat features—measured at hatch—of successful nests, depredated nests, and random sites; lateral (r = 0.66) and overhead (r = 0.35) concealment were microhabitat variables most correlated with canonical discriminant functions. We also modeled daily survival rate of nests as a function of year, linear and quadratic trends with nest age, nest initiation date, and seven microhabitat variables. Nest survival from a time-constant model (i.e. Mayfield nest-success estimate) was 0.35 (95% CL: 0.27, 0.43). Estimates of nest success were lower than those measured at Redberry Lake in the 1970s and 1980s. Nest survival increased throughout the laying period and stabilized during incubation, and showed positive relationships with nest concealment and distance to water and a negative relationship with distance to edge. Considering those factors, a model-averaged estimate of nest survival was 0.24 (95% CL: 0.09, 0.42). We concluded that White-winged Scoters selected nesting habitat adaptively, because (1) successful sites were more concealed than depredated sites; (2) nest sites (both successful and depredated) had higher concealment than random sites; and (3) nest sites were on islands, where success is greater than on the mainland.
Clinal Variation in Vocalizations of an Antbird (Thamnophilidae) and Implications for Defining Species Limits
Authors: Isler Morton L. , Isler Phyllis R. , Brumfield Robb T. 
Published: September 2019

Abstract
In avian taxa in which vocalizations are considered innate, such as suboscine passerines, vocal characters are increasingly being used to help determine whether populations have achieved species status. In comparing vocal characteristics of distant populations, however, one must be concerned with the possibility of character gradation through intermediate populations. The first quantitative study of a species in a suboscine family to test for clinal vocal variation, our vocal study found clinal variation in the pace (number of notes per second) of male loudsongs, and revealed that the geographic pattern of the clines was consistent with genetic variation found in the companion molecular study (Brumfield 2005). The result underscores the necessity of searching for intermediacy when analyzing vocalizations of geographically distant populations. Furthermore, given that male loudsong pace was the only vocal character that varied across the intergrading populations, the result also provides support to the guideline that one should expect thamnophilid species to differ in at least three vocal characters (Isler et al. 1998) and indicates that this degree of vocal character differences can be a valuable “yard stick” in determining which thamnophilid populations have achieved biological species status.
Weather in The Breeding Area and During Migration Affects the Demography of a Small Long-Distance Passerine Migrant
Authors: Stokke Bård G. , Møller Anders Pape , Sæther Bernt-Erik , Rheinwald Goetz , Gutscher Hans 
Published: September 2019

AbstractMigratory birds are subject to the effects of various weather systems during the year. Fluctuations in population size may depend on survivorship of juveniles and adults at various stages of the annual cycle. Severe weather conditions can lower survival, especially in migrating passerines that feed on insects. We investigated the effects of climate and density dependence on survival in a population of Common House-Martins (Delichon urbicum), including variables of weather experienced both in their breeding areas and during autumn migration. Unfavorable weather conditions during autumn migration had a severe negative effect on adult apparent survival, irrespective of sex; whereas temperature in the breeding area and population size explained a significant proportion of variance in juvenile survival. Thus, weather conditions experienced in different areas can regulate various age classes in different ways, which suggests that climate change can have a significant but complex influence on demography in passerine populations.
Molecular Phylogenetics of the Ramphastos Toucans: Implications for the Evolution of Morphology, Vocalizations, and Coloration
Authors: Weckstein Jason D. 
Published: September 2019

AbstractI reconstructed the phylogeny of 12 Ramphastos toucan taxa using mitochondrial DNA (mtDNA) sequences. This analysis identified two major groups, including a monophyletic smooth-billed yelping clade and a clade including most, but not all, the channel-keel-billed croakers. Within the R. tucanus and R. vitellinus groups, uncorrected mtDNA divergences are relatively low and mtDNA sequences from several subspecies are paraphyletic. One exception to low divergences within the R. vitellinus group is R. v. ariel from southeastern Brazil, which on average differs from all other R. vitellinus sampled by 2.9%. Character reconstructions on the phylogeny indicate that the ancestral Ramphastos was most likely a large-bodied channel- keel-billed croaker. Furthermore, an assessment of the patterns of bill shape, voice, and both plumage and bare-part coloration characters suggests that bill shape and voice have significant phylogenetic signal but that color characters do not. Sympatric Ramphastos taxa are not closely related in the phylogeny; therefore, character reconstructions indicate that the extreme similarity in coloration patterns between many sympatric Ramphastos pairs is most likely attributable to a combination of convergence or parallelism (homoplasy) and shared ancestral character states (symplesiomorphy).Filogenética Molecular de los Tucanes del Género Ramphastos: Implicaciones para la Evolución de la Morfología, las Vocalizaciones y la Coloración
Effects of Incubation Conditions and Offspring Sex on Embryonic Development and Survival in the Zebra Finch (Taeniopygia Guttata)
Authors: Gorman Helen E. , Orr Kate J. , Adam Aileen , Nager Ruedi G. 
Published: September 2019

AbstractSuboptimal conditions during embryonic development can affect offspring fitness. Both egg quality and incubation behavior can affect hatching success, hatching mass, and subsequent offspring performance. These effects may differ between male and female offspring. We manipulated the prebreeding body condition of Zebra Finches (Taeniopygia guttata), using diets of different protein content. To separate possible effects on egg quality of parental body condition and incubation conditions, we did a cross-fostering experiment. We analyzed embryo survival and hatching mass with respect to body condition of the egg-laying parent, body condition of the incubating foster parent, and offspring sex. Embryos were not affected by the condition of the egg-laying parent. Eggs incubated by parents in better condition suffered less embryo mortality than those incubated by parents in poorer condition, but only when overall embryo mortality was low. Hatching mass was also affected by the incubating foster parent’s body condition. And hatchlings incubated by parents in good condition were heavier than those incubated by parents in poor condition. Female hatchlings from late-laid eggs were heavier, in comparison with the size of the egg from which they hatched, than female hatchlings from earlier-laid eggs. No such effect was found for males. Therefore, male and female embryos may differ in their sensitivity to suboptimal conditions during embryonic development. These results suggest that parental body condition during incubation can affect offspring fitness.Efectos de las Condiciones de Incubación y el Sexo de las Crías sobre el Desarrollo Embrional y la Supervivencia en Taeniopygia guttata
Nest Survival in Dusky Canada Geese (Branta Canadensis Occidentalis): Use of Discrete-Time Models
Authors: Grand James B. , Fondell Thomas F. , Miller David A. , Anthony R. Michael 
Published: September 2019

AbstractThe Dusky Canada Goose (Branta canadensis occidentalis) population that breeds in the Copper River Delta, Alaska, has declined substantially since the late 1970s. Persistent low numbers have been attributed to low productivity in recent years. We examined patterns in survival rates of 1,852 nests to better understand ecological processes that influenced productivity during 1997-2000. We compared 10 nonparametric models of daily survival rate of nests (DSR) that included variation among years, calendar dates, nest initiation dates, and nest ages with equivalent models based on parametric functions. The unequivocal best model included patterns of DSR that varied among discrete periods of years, calendar dates, and nest ages. Generally, DSR was low early in the nesting season and higher midseason. Across years, patterns in DSR were most variable early and late in the nesting season. Daily survival rates of nests declined between the first and second week after initiation, increased until the fourth week, and then declined during the last week before hatch. Nest survival probability estimates ranged from 0.07 to 0.71 across years and nest initiation dates. Mean rates of nest survival ranged between 0.21 and 0.31 each year. We suggest (1) considering models that do not limit estimates of daily nest survival to parametric forms; (2) placing greater emphasis on sample size when nests are rare, to obtain accurate estimates of nest survival; and (3) developing new techniques to estimate the number of nests initiated.Supervivencia de los Nidos en Branta canadensis occidentalis: Uso de Modelos de Tiempo Discreto
Telomere Shortening in a Long-Lived Marine Bird: Cross-Sectional Analysis and Test of an Aging Tool
Authors: Juola Frans A. , Haussmann Mark F. , Dearborn Donald C. , Vleck Carol M. 
Published: September 2019

AbstractA correlation between length of telomere restriction fragments (TRFs) and age has recently been demonstrated in several bird species. Comparisons of different-aged individuals within a population have shown that TRFs typically shorten with age and that this shortening continues throughout the life span of the species. In addition, it has been shown that telomere rate-of-change (TROC) correlates tightly with life span across several bird species. Previous studies of long-lived birds, however, have shown exceptions to these trends, demonstrating no declines in TRF length in adults in some cases and increases in TRF length with age in other cases. Here, we report known ages of individuals from a colony of Great Frigatebirds (Fregata minor) based on recaptures of leg-banded birds, including two individuals that were at least 44 years of age, the oldest Great Frigatebirds ever reported. Using a previously developed molecular technique, we report a predictable, nonlinear decline of TRF length with age in this population. Telomere restriction fragments decline more rapidly early in life but continue to shorten throughout the life span examined. The rate of decline in TRF for this species does not fit the tight correlation previously reported between TROC and life span in other species. Finally, we tested the ability to estimate age and age structure of breeding females on the basis of the calibration of TRF length and individuals of known age. Because of the slow telomere-attrition rate and the variability observed in TRF lengths at given ages, estimations of age of individuals and of estimated age structure of breeding birds in this population are not particularly reliable.Encogimiento del Telómero en un Ave Marina Longeva: Análisis de Secciones Cruzadas y Evaluación de una Herramienta de Envejecimiento
Occupancy Estimation and Modeling
Authors: Peterson James T. , Mordecai Rua S. 
Published: September 2019

Abstract
The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists' Union.
Vegetative and Fruit Resources as Determinants of Habitat use by Mature-Forest Birds During the Postbreeding Period
Authors: Vitz Andrew C. , Rodewald Amanda D. 
Published: September 2019

AbstractRecent studies have demonstrated that many birds of mature forests heavily use early-successional habitat during the postbreeding period. Two frequently invoked hypotheses to explain these shifts are that postbreeding birds select (1) dense cover to reduce risk of predation and (2) abundant fruit resources to facilitate foraging. Using mist nets between 15 June and 16 August in 2002 and 2003, we captured mature-forest birds during the postbreeding period in 12 regenerating hardwood clearcuts (three to seven years old) in southeast Ohio. Vegetation structure and fruit resources were measured at nine net locations within each clearcut. We applied an information-theoretic approach, where we used vegetative and fruit variables as predictors in seven a priori models to evaluate how habitat factors might explain capture rates. In two seasons, we captured 1,089 hatch-year (HY) and 445 after-hatch-year (AHY) postbreeding birds of 32 mature-forest species. In general, models reflecting habitat structure (density of low vegetation, canopy height) best explained variation in capture rates, which were negatively related to the density of low vegetation (<1.5 m) and positively related to canopy height. Extremely dense low vegetation may be disadvantageous if it inhibits movements and provides cryptic locations for ground predators. Instead, habitats with greater vertical structure (e.g., taller vegetation) and relatively less dense low vegetation below may provide better protection from aerial and ground predators. Overall, results suggest that vegetation structure may explain high use of early-successional forests by many birds during the postbreeding period, though fruit may be the most important factor for seasonal frugivores.Recursos Vegetativos y de Frutos como Determinantes del Uso de Hábitat por Aves de Bosque Maduro Durante el Período Posterior a la Reproducción
Aspects of the Hindlimb Morphology of Some Australian Birds of Prey: A Comparative and Quantitative Study
Authors: Einoder Luke D. , Richardson Alastair M. M. 
Published: September 2019

AbstractWe quantified the extent of adaptive radiation in the evolution of the hindlimb in the bird-of-prey community on Tasmania. Assessments of the ecological capabilities of raptor species are often based on a visual inspection of their hindlimb structure, with little recourse to direct biomechanical or functional evidence. We examined the links between hindlimb structure and patterns of diet, foraging, and habitat use in raptors by analytically investigating tarsus, toe, and talon measurements. We identified groupings on the basis of dietary preference, hunting-killing technique, and phylogeny. We found that the bird-catching specialists, which possessed relatively long digits with short talons, were consistently separable. The large-mammal and fish specialists were equipped with relatively short and robust tarsi, and short digits with long and robust talons. The hindlimbs of medium-mammal specialists were characterized by long digits and a large digit 1 talon. However, the generalist group did not possess any specializations, because their structural elements were comparable to those of other dietary groups. An association was found between the ratio of toe to talon length and the selective pressures of prey capture and ease of killing. Morphological variation in this feature was consistent with phylogeny, because the Accipitridae were characterized by a larger ratio of toe to talon length on digits 1 and 2 than the Falconidae, and the diurnal raptors possessed an interdigital pattern of larger variation in ratio of toe to talon length than the nocturnal raptors. No link was found between dietary habit and tarsus length or robustness, because these features were apparently attributed to variations in hunting style. Our analysis highlights the interrelationship between the morphology of hindlimb structure and the functional pressures associated with predatory lifestyles.Aspects de la morphologie des membres postérieurs de quelques oiseaux de proie australiens : Une étude comparative et quantitative
The Sound Approach to Birding: A Guide to Understanding Bird Sound
Authors: Robbins Chandler S. 
Published: September 2019

Abstract
The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists’ Union.