bluuebunny/crossref_metadata_2025 huggingface dataset:
Geographic Variation in Brown-Headed Cowbird (Molothrus Ater) Parasitism on Dickcissels (Spiza Americana) in Great Plains Tallgrass Prairie
Authors: Jensen William E. , Cully Jack F.
Published: September 2019

The incidence of brood parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds“) within host species typically reflects the continental pattern in cowbird abundance across North America, where parasitism is heaviest in the Great Plains. However, we found considerable variation in cowbird parasitism on Dickcissel (Spiza americana) nests within a subregion of the Great Plains (the Flint Hills), where the highest levels of cowbird parasitism on grassland bird nests had been previously reported. Local parasitism frequencies on Dickcissel nests varied latitudinally across the Flint Hills, ranging from 0% to 92% of nests parasitized. Interestingly, we found no obvious patterns in habitat or host attributes that were associated with this steep geographic gradient in brood parasitism. Cowbird parasitism on Dickcissel nests was not correlated with the vertical density of local prairie vegetation, mean nest distance to edge, proportion of forest to grassland habitat surrounding study sites (≤5 to 10 km), geographic variation in host abundance, or Dickcissel density or nest initiation dates. Parasitism frequencies and intensities (number of cowbird eggs per parasitized nest) on Dickissel nests were only significantly related to variation in local female cowbird density. Dickcissel clutch size and apparent fledging success were negatively correlated with local cowbird parasitism levels. Geographic patterns in cowbird abundance within and among regions should be considered when establishing conservation areas for grassland birds or other cowbird hosts of concern.
Time-Specific Variation in Passerine Nest Survival: New Insights into Old Questions
Authors: Grant Todd A. , Shaffer Terry L. , Madden Elizabeth M. , Pietz Pamela J.
Published: September 2019

Understanding nest survival is critical to bird conservation and to studies of avian life history. Nest survival likely varies with nest age and date, but until recently researchers had only limited tools to efficiently address those sources of variability. Beginning with Mayfield (1961), many researchers have averaged survival rates within time-specific categories (e.g. egg and nestling stages; early and late nesting dates). However, Mayfield’s estimator assumes constant survival within categories, and violations of that assumption can lead to biased estimates. We used the logistic-exposure method to examine nest survival as a function of nest age and date in Clay-colored Sparrows (Spizella pallida) and Vesper Sparrows (Pooecetes gramineus) breeding in north-central North Dakota. Daily survival rates increased during egg laying, decreased during incubation to a low shortly after hatch, and then increased during brood rearing in both species. Variation in survival with nest age suggests that traditional categorical averaging using Mayfield’s or similar methods would have been inappropriate for this study; similar variation may bias results of other studies. Nest survival also varied with date. For both species, survival was high during the peak of nest initiations in late May and early June and declined throughout the remainder of the nesting season. On the basis of our results, we encourage researchers to consider models of nest survival that involve continuous time-specific explanatory variables (e.g. nest age or date). We also encourage researchers to document nest age as precisely as possible (e.g. by candling eggs) to facilitate age-specific analyses. Models of nest survival that incorporate time-specific information may provide insights that are unavailable from averaged data. Determining time-specific patterns in nest survival may improve our understanding of predator-prey interactions, evolution of avian life histories, and aspects of population dynamics that are critical to bird conservation.
The Howard and Moore Complete Checklist of the Birds of the World
Authors: Kratter Andrew W.
Published: September 2019

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 refl ect the opinions of the editors or any offi cial policy of the American Ornithologists' Union.
Reproductive Success Across The Black-Capped Chickadee (Poecile Atricapillus) and Carolina Chickadee (P. Carolinensis) Hybrid Zone in Ohio
Authors: Bronson C. L. , Grubb Thomas C. , Sattler Gene D. , Braun Michael J.
Published: September 2019

Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (P. carolinensis) hybridize in an east-west band from New Jersey to Kansas. Within the past century, the Ohio portion of this hybrid zone and the Carolina Chickadee range to the south have been moving northward, whereas the Black-capped Chickadee range has retracted. In Ohio, we characterized the genetic composition of the hybrid zone using five diagnostic molecular loci. Although there was no evidence of assortative mating in the center of the hybrid zone, we found a relative paucity of genetically intermediate breeding females as compared with breeding males. That suggests viability selection against female hybrids, in line with Haldane’s rule. On the basis of reproductive variables (number of nestlings, reproductive success), we found a decrease in productivity of breeding pairs in the hybrid zone that is significantly and positively related to their probability of producing homozygous offspring at each autosomal or sex-linked locus. We also found that the decrease in productivity was significantly and positively related to the genetic composition of the male of the pair (i.e. pure male chickadees more productive). These data strongly suggest that hybrids are at a selective disadvantage. Because the zone of reduced reproductive success was considerably narrower than the zone of introgression, our results demonstrate that genetic introgression is occurring in the face of substantial selection against hybrids.

Éxito Reproductivo a través de la Zona de Hibridación de Poecile atricapillus y P. carolinensis en Ohio
Adult Survival Estimates From Two Atlantic Puffin (Fratercula Arctica) Colonies in The Gulf of Maine
Authors: Breton André R. , Diamond Antony W. , Kress Stephen W.
Published: September 2019

We report survival probabilities for 148 breeding adult Atlantic Puffins (Fratercula arctica) monitored through capture-mark-resight at two colonies for 11 years (1992–2003). The colonies, Eastern Egg Rock and Seal Island, are ∼42 km apart in the Gulf of Maine. Support for competing models in the program MARK suggests constant survival of 0.95 ± 0.01 (SE) that is independent of colony. Our high survival probability is consistent with published estimates for Atlantic Puffins and other long-lived seabirds. No time-variance contrasts with many long-term seabird studies, which often report high survival in most years, broken occasionally by low-survival events. However, a post-hoc observation of survival estimates from the time-dependent model suggests that there may have been at least two low-survival events in our time-series; sparse data may have precluded detection by our models. In this study, each bird received an individually engraved, plastic, field-readable leg band, as well as the standard metal band. Using an index of band readability, we show that plastic bands wore rapidly, resulting in accumulating losses of engraved characters through time. Degradation and loss of marks is a common source of overdispersion in capture-mark-re-encounter data and results in underestimated sampling variances. In the presence of a 70% reduction in band readability over eight years, an estimate of the adjusted overdispersion factor (ĉ = 1.14) identified very little overdispersion in our data. Overdispersion was avoided by double banding and intensively resighting metal bands.

Estimation de la Survie Adulte de Deux Colonies de Fratercula arctica dans le Golfe du Maine
Quantifying Differential Responses to Fruit Abundance by Two Rainforest Birds Using Long-Term Isotopic Monitoring
Authors: Herrera M. L. Gerardo , Hobson Keith A. , Hernández C. Patricia , Rodríguez G. Malinalli
Published: September 2019

Most tropical passerines feed on insects, fruit, or a combination of the two. The sugary pulps of fruit have lower amounts of protein than insects. We used stable-nitrogen isotope analysis (δ15N) of blood from two tropical rainforest birds that regularly feed on fruit—Red-throated Ant-Tanager (Habia fuscicauda) and Ochre-bellied Flycatcher (Mionectes oleagineus)—to quantify the relative amounts of assimilated protein from animal and plant sources. Because fruit and insect abundances vary seasonally in the tropics, the study was conducted during one year in Los Tuxtlas, Mexico. The study site has one major fruiting peak between April and July and a secondary peak between September and October. Some insects are more abundant from May to August. Red-throated Ant-Tanagers and Ochre-bellied Flycatchers rely heavily on insect protein when fruit is scarce, and then steadily increase their input of fruit protein as fruit abundance increases. Red-throated Ant-Tanagers rely almost entirely on fruit protein during the major fruiting peak, whereas Ochre-bellied Flycatchers have the largest input of fruit protein during the secondary fruit peak. Incubation in both species occurs from June to August, and most incubating individuals rely on a mixture of insects and fruit. In both species, examination of fecal contents showed the ingestion of the largest number of fruit species during the major fruiting peak.

Cuantificación de la Respuesta Diferencial a la Abundancia de Frutos por Dos Especies de Aves Selváticas Mediante el Monitoreo Isotópico a Largo Plazo
Large-Scale Movement Patterns Between Song Dialects in Brown-Headed Cowbirds (Molothrus Ater)
Authors: Anderson Kurt E. , Rothstein Stephen I. , Fleischer Robert C. , O’Loghlen Adrian L.
Published: September 2019

Extensive past research has attempted to determine whether song dialects represent reproductively isolated social systems, with individuals tending to spend their entire lives in a single dialect. We addressed that issue by analyzing banding data for Brown-headed Cowbirds (Molothrus ater) on the eastern slope of the Sierra Nevada of California. For 14 years, 1,393 juveniles and 2,568 mature individuals were banded along a 40-km span encompassing three dialects. Of those juvenile and mature birds, 7.9% and 12.1%, respectively, were recaptured in a later year. All classes of mature birds (second-year males, older males, and females) had significantly higher recapture rates than birds banded as juveniles, but there were no differences among the mature classes. Overall, 22.7% of 110 juveniles recaptured in a subsequent year were trapped in a dialect region other than the one in which they were banded, as compared with 8.1% of 310 mature birds. Neither juvenile nor mature birds showed sex-related differences in proportions recaptured in subsequent years in different dialect regions. Birds in all sex-age classes were more likely to have moved to a new dialect region when recaptured in a subsequent year than when recaptured within the year, which suggests that apparent movements between years were cases of dispersal, rather than short-term foraging trips. Although our banding data cannot confirm gene flow, the high levels of movement they show agree with genetic and morphometric studies indicating high levels of gene flow among these cowbird dialects.

Patrones de Movimiento de Gran Escala entre Dialectos del Canto de Molothrus ater
Cultural Divergence Within Novel Song in The Black-Capped Chickadee (Poecile Atricapillus)
Authors: Gammon David E. , Baker Myron C. , Tipton John R.
Published: September 2019

Geographic variation in learned vocalizations is commonly attributed, in part, to imperfect song learning, but rarely has this been documented. Additionally, we know little about how spatial structure of populations affects geographic divergence in song. Using novel fee-bee song in Black-capped Chickadees (Poecile atricapillus) in Fort Collins, Colorado, we investigated both of those concepts by recording songs from juveniles at the time of natal dispersal and from adults at study sites along a continuous riparian corridor and in small isolated populations north of Fort Collins. Acoustic differences within juveniles' songs corresponded to acoustic differences distinguishing the songs of adults from separate study sites. We also found more acoustic divergence among the small isolated populations than among the continuously distributed riparian populations, and we found that the song-type grouping most similar in acoustic structure to the stereotyped continental fee-bee diverged the least. These findings suggest that song variants introduced by developing juveniles can indeed account for geographic variation and that song diverges more in small isolated populations.

Divergencia Cultural en los Cantos Aprendidos en Poecile atricapillus
Wing Morphology and Flight Behavior of Some North American Hummingbird Species
Authors: Stiles F. Gary , Altshuler Douglas L. , Dudley Robert
Published: September 2019

We explored the relationship between wing morphology and flight behavior with respect to sex and age in five species of North American hummingbirds. We first measured the length, chord or “width,“ and area of entire hummingbird wing planforms. We then calculated additional parameters of wing shape and size, including aspect and shape ratios, degree of taper or “pointedness,“ wing loading, and wing disc loading (WDL). Wings of adult males are not only shorter but also more narrow and tapered than those of adult or immature females; immature males have larger wings and lower WDL, more like those of females. A proposed relationship between WDL and territorial behavior and dominance is not supported, given that adult and immature males show similar feeding territoriality outside the breeding season but females rarely do. The more extreme and divergent wings of adult males probably reflect sexual selection in connection with aerial displays that include species-specific sound effects given during the breeding season. North American species are unusual among hummingbirds in showing reversed sexual size-dimorphism (males smaller, with relatively shorter wings), a feature shared with some other small hummingbirds, notably the “Pygmornis“ hermits. Attempts to explain hummingbird foraging and territorial behavior on the basis of differences in WDL have failed because many aspects of wing morphology, physiology, and flight behavior were not taken into account. Several wing parameters appear more related to other modes of flight than to strategies of nectar exploitation, and the morphology of any given wing represents a compromise between the often conflicting aerodynamic demands of different flight modes. Understanding hummingbird flight will require broad comparative studies of wing morphology and wingbeat kinematics in relation to flight behavior, and new theoretical models and experimental data will be needed to elucidate physiological and aerodynamic mechanisms underlying forward flight and maneuvering.

Morfología Alar y Comportamiento de Vuelo de Unas Especies de Colibríes de Norteamérica
Overlap in Diets and Foraging of Common Murres (Uria Aalge) and Rhinoceros Auklets (Cerorhinca Monocerata) After the Breeding Season
Authors: Lance Monique M. , Thompson Christopher W.
Published: September 2019

Common Murres (Uria aalge; hereafter “murres“) and Rhinoceros Auklets (Cerorhinca monocerata; hereafter “auklets“) breed and forage sympatrically over much of their range. They have similar diets during the breeding season, which suggests that they partition prey during the breeding season by foraging (1) at different locations, (2) at different times of day, (3) at different water depths, (4) on different proportions of the same prey species, or (5) some combination of the four. We examined possible mechanisms of niche partitioning during late summer and fall in Puget Sound, Washington, in 1993-1996. Murres and auklets fed mainly on Pacific herring (Clupea pallasii, occurring in 74.2% and 48.1%, respectively, of gastrointestinal tracts with contents), Pacific sand lance (Ammodytes hexapterus; 45.8% and 62.3%), and salmonid (Oncorhynchus spp.) species (21.9% and 9.7%). Auklets also consumed considerable amounts of threespine stickleback (Gasterosteus aculeatus; 26.6%). Murres and auklets did not differ significantly (1) in their diet (between age classes or sexes of either species, or among years); (2) in mean lengths of Pacific herring (101 and 109 mm, respectively) and Pacific sand lance (82 and 86 mm) they consumed; or (3) in the mean depth (7–8 m) at which they were entangled in gill nets. Dietary diversity was low, with most gastrointestinal tracts containing only one or two prey species in both murres and auklets. Murres were caught and therefore presumably feed more frequently in the afternoon and evening; whereas auklets were entangled more often in early morning. We found differences between murres and auklets in the diel chronology of prey taken, which may partly explain how murres and auklets coexist during the breeding season and months thereafter, prior to auklet emigration from Puget Sound.

Chevauchement du Régime Alimentaire et de la Quête Alimentaire chez Uria aalge et Cerorhinca monocerata après la Saison de Reproduction
Temporal and Geographic Patterns of Age-Specific Gull Plumage in Relation to Potential Exposure to Polychlorinated Biphenyls
Authors: Sampieri Sara J. , Clotfelter Ethan D.
Published: September 2019

Study skins of Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus) collected over a period of ∼150 years in the northeastern United States were used to test the hypothesis that potential exposure to polychlorinated biphenyls (PCBs) has an effect on age-related plumage coloration. We found no changes in the average age class (as determined by plumage) of gulls collected before and after 1930 (date PCBs began to be used) and no differences in average age class in birds collected near PCB-contaminated sites versus those collected far from such sites. We found significant skews in the age distributions of birds in our sample because of an under-representation of birds of intermediate age classes, but those skews were similar in pre- and post-1930 data sets and thus likely represent sampling errors and not the effects of PCBs. There was no difference in the age distribution of gulls collected near or far from contaminated sites. Our study, albeit indirectly, shows no evidence that PCB exposure affects plumage maturation rate in piscivorous gulls.

Patrons Géographiques et Temporels du Plumage chez les Laridés en Fonction de l’\bcp\A\ecp\ge et de l’Exposition Potentielle aux Polychlorobiphényles
Body Composition and Flight Ranges of Bar-Tailed Godwits (Limosa Lapponica Baueri) From New Zealand
Authors: Battley Phil F. , Piersma Theunis
Published: September 2019

Body composition analysis was performed on 37 Bar-tailed Godwits (Limosa lapponica baueri) that had been illegally shot during migratory fueling in northern New Zealand in March 1992. Adults (n = 35) were heavy (442–721 g), with fat loads of 30–45% of body mass. Two first-year males had only 5.4% and 8.9% fat, respectively, and had 13% less lean (fat-free dry) tissue than the average adult male. Males and females scaled along the same size axes, with little overlap between the sexes (females were larger). Larger birds carried more fat, but fat loads did not differ systematically with size (and, therefore, sex). Fatter birds (after accounting for body size) had larger flight muscle and lung masses, implying premigratory hypertrophy. Males that were not in body molt were fatter, but less colorful, than molting birds. They were also longer-winged and had larger testes but smaller intestines and salt glands, which suggests that they may belong to a subpopulation with a different fueling and molt strategy. Comparison between L. l. baueri and a smaller subspecies (L. l. taymyrensis) indicated that although the two subspecies scaled along the same lean mass-size axes, L. l. baueri deposited much more fat for their body size (1.7 × more than the equivalent-sized L. l. taymyrensis). On the basis of estimated travel costs for L. l. taymyrensis, predicted flight ranges for L. l. baueri ranged from 6,000 to 8,600 km, depending on whether wind assistance is assumed. That suggests that direct flights from New Zealand to southeastern or eastern Asia are possible (e.g. Philippines, 7,200 km; Japan, 8,700; South Korea, 9,100 km).

Composition Corporelle et Distance de Vol chez Limosa lapponica baueri de Nouvelle-Zélande
Evidence of Latitudinal Sexual Segregation Among Migratory Birds Wintering in Mexico
Authors: Komar Oliver , O’Shea B. J. , Peterson A. Townsend , Navarro-Sigüenza Adolfo G.
Published: September 2019

Latitudinal sexual segregation during the nonbreeding season, in which males tend to winter farther north than females, is known to occur in many temperate-zone bird species. This pattern, however, has rarely been reported in species wintering in tropical regions. We investigated latitudinal sexual segregation in 45 Nearctic-Neotropical migratory bird species that winter in Mexico, using specimen records from 35 natural-history museums. We found significant latitudinal segregation in nine species: Yellow-bellied Sapsucker (Sphyrapicus varius), Swainson’s Thrush (Catharus ustulatus), Orange-crowned Warbler (Vermivora celata), Yellow Warbler (Dendroica petechia; aestiva group), Yellow-rumped Warbler (Dendroica coronata; coronata group), Black-and-white Warbler (Mniotilta varia), Ovenbird (Seiurus aurocapilla), Wilson’s Warbler (Wilsonia pusilla), and Indigo Bunting (Passerina cyanea). In most cases, males predominated in the northern part of species’ winter ranges and females in the south, but the trend was reversed in Indigo Buntings. Discovering the frequency of latitudinal sexual segregation in Neotropical migratory birds will influence understanding of avian ecology and migration systems.

Evidencia de la Segregación Latitudinal Sexual en Aves Migratorias durante el Invierno en México
Phylogeography of The Mallard (Anas Platyrhynchos): Hybridization, Dispersal, and Lineage Sorting Contribute to Complex Geographic Structure
Authors: Kulikova Irina V. , Drovetski Sergei V. , Gibson Daniel D. , Harrigan Ryan J. , Rohwer Sievert , Sorenson Michael D. , Winker Kevin , Zhuravlev Yuri N. , McCracken Kevin G.
Published: September 2019

Population genetic variation in Mallards (Anas platyrhynchos; n = 152) from Western Russia, North Asia, the Aleutian Islands, and mainland Alaska was investigated using 667 base pairs of the 5′-end of the mitochondrial DNA (mtDNA) control region. DNA sequencing revealed two clades that correspond to Avise et al.’s (1990) group A and B mtDNA haplotypes. Group A haplotypes (80.3%) were wide- spread in all localities from Western Russia to Alaska. Group B haplotypes (19.7%), by contrast, were found primarily in mainland Alaska, where they occurred at high frequency (77.4%), but they also occurred at low frequencies (declining east to west) in the Aleutian Islands (11.8%) and the Primorye region of North Asia (4.4%). Group B haplotypes were not observed in Western Russia or elsewhere in North Asia outside Primorye. Consequently, Mallards exhibited substantial genetic structure between Old World and New World (ΦST = 0.4112–0.4956) but possessed little genetic structure within the Old World continental area (ΦST = 0.0018). Nonetheless, when only group A haplotypes were included in the analysis, Mallards from the Aleutian Islands differed (albeit with low levels of divergence) from each of the other three sampled regions in the Old World and New World (ΦST = 0.0728–0.1461, P < 0.05). Mallards inhabit the Aleutian Islands year-round, so these insular populations may be isolated from Asian and North American populations that occur in the Aleutian Islands only during migration. Overall weak phylogeographic structure and low genetic differentiation within Asia, and between Asia and North America when only group A haplotypes were evaluated, is probably explained by large long-term population sizes and significant intra-continental dispersal. The coexistence and nonrandom distribution of two divergent mtDNA haplotype lineages in Alaska, the Aleutian Islands, and the Primorye region of North Asia, but not in Western Russia or elsewhere in North Asia, is consistent with historical and contemporary hybridization and incomplete sorting of A and B mtDNA haplotype lineages in Mallards and closely related species inhabiting the Old World and New World.
A New Species of Scimitar-Babbler (Timaliidae: Jabouilleia) From the Sub-Himalayan Region of Myanmar
Authors: Rappole John H. , Renner Swen C. , Shwe Nay Myo , Sweet Paul R.
Published: September 2019

An expedition of representatives from the Myanmar Nature and Wildlife Conservation Division and the Smithsonian National Zoological Park's Conservation and Research Center visited the town of Naung Mung on the Nam Tisang River in the extreme northern portion of Kachin State, Myanmar, during February 2004. The town is located in the sub-Himalayan region of the country at 27°29′N, 97°48′E, elevation 540 m, 118 km south of the Tibetan border and 53 km west of the border with Yunnan Province, China. The purpose of the trip was to inventory the poorly known avifauna of the premontane temperate rainforest habitat at that site. On 6 February 2004, we captured two scimitar-babblers that appeared to be representatives of the genus Jabouilleia. An additional individual of the taxon was captured in the same vicinity on 8 February 2004. These were the first records for Jabouilleia from Myanmar, and subsequent investigation showed that these specimens were members of a previously undescribed species, which we designate Jabouilleia naungmungensis, the Naung Mung Scimitar-Babbler.

Une Nouvelle Espèce de Jabouilleia (Timaliidae) dans la Région sub-Himalayenne de la Birmanie
Molt Strategies and Age Differences in Migration Timing Among Autumn Landbird Migrants in Southwestern Idaho
Authors: Carlisle Jay D. , Kaltenecker Gregory S. , Swanson David L.
Published: September 2019

Intraspecific patterns of autumn migration timing are not well known, particularly in the western United States. Here, we (1) describe autumn migration timing and age ratios of landbird migrants in southwestern Idaho, (2) examine differences in timing among age and sex classes, and (3) demonstrate how prebasic molt strategies affect migration timing differences between age classes. As a group, Neotropical migrants were most common from late July through early September, whereas temperate migrants were most common from mid-September into early October. Proportion of hatch-year birds was 74.5% for all migrants combined and ranged from 33.3% to 100% for individual species. Timing differences between sex classes were detected in only a few species and no general patterns emerged. In 22 of 31 Neotropical and temperate migrants examined, there were significant differences in timing between adults and hatch-year birds. In species in which adults begin fall migration before replacing flight feathers, adults migrated earlier than hatch-year birds. Conversely, in species in which adults molt flight feathers on or near the breeding grounds before departing on fall migration, hatch-year birds migrated earlier than adults in all but one case. Therefore, it appears that molt strategy is a powerful determinant of intraspecific migration timing differences and, to our knowledge, this is the first study to document this pattern among migrant passerines of North America.

Estrategias de Muda y Diferencias en el Momento de Migración Otoñal en Migrantes Terrestres en el Suroeste de Idaho
Resource Availability Controls Bird-Assemblage Composition Through Interspecific Aggression
Authors: Mac Nally Ralph , Timewell Christopher A. R.
Published: September 2019

High-value resources are often defended aggressively by consumers, which can alter assemblage structure and dynamics. Here, we describe a system of nectarivorous bird assemblages exploiting pockets of eucalypt woodlands that differ dramatically in flowering and provision of nectar. The behavioral dominant, the Red Wattlebird (Anthochaera curunculata), aggressively reduces the occurrence and activities of other honeyeaters of the genera Lichenostomus and Melithreptus on sites of intense flowering. The latter genera predominate in moderately flowering areas, but few honeyeaters occupy poorly flowering sites. To understand such systems, in which temporal variation in habitat quality can be great, one needs to consider not only the disparity in habitat quality among locations but also the spatial extent of habitats of different quality. Isoleg analysis is a theoretical tool developed to understand how dominant and subordinate species partition habitats as a function of their respective densities. Our results suggest that isoleg analysis needs to be developed with spatial explicitness to capture variation in extent of habitats of different qualities and consequent effects on the usefulness of aggression for domination of resources.

La Disponibilidad de Recursos Controla la Composición de los Ensambles de Aves a través de las Agresiones Interespecíficas
No Support for a Genetic Basis of Mandible Crossing Direction in Crossbills (Loxia SPP)
Authors: Edelaar Pim , Postma Erik , Knops Peter , Phillips Ron
Published: September 2019

Unusual among birds, the bill tips in crossbills (Loxia spp.) overlap in the vertical plane, with the tip of the lower mandible to either the left or right of the tip of the upper mandible when viewed from above. Patterns observed in wild populations and experimental foraging data suggest that a 1:1 ratio of left- to right-crossing individuals is maintained by frequency-dependent natural selection in some populations, and that genetic drift causes deviation from a 1:1 ratio in other populations. Both processes require a genetic basis for this remarkable polymorphism, yet few data are available that address whether, and how, mandible crossing direction is heritable. To test for a genetic basis of this trait (single or quantitative, autosomal or sex-linked), we analyzed resemblance in mandible crossing direction between related captive-bred individuals of several crossbill taxa with standard statistical techniques as well as modern animal model methodology. Surprisingly, we did not find statistically significant support for a genetic basis of mandible crossing direction. Comparisons of the ratio of left- to right-crossing males and females in wild populations also did not support a sex-linked quantitative genetic basis. We conclude that mandible crossing direction may have uncharacteristically low heritability, but we cannot rule out that it is nongenetically determined.

La Dirección de Cruzamiento de la Mandíbula en las Especies de Loxia no Presenta Base Genética
Phylogeography of the American Woodcock (Scolopax Minor): Are Management Units Based on Band Recovery Data Reflected in Genetically Based Management Units?
Authors: Rhymer Judith M. , McAuley Daniel G. , Ziel Heather L.
Published: September 2019

Information on population connectivity throughout the annual cycle has become more crucial, because populations of many migratory birds are in decline. One such species is the American Woodcock (Scolopax minor), which inhabits early-successional forests in eastern North America. Although band recoveries have proved useful for dividing populations of this game bird species into an Eastern Region and Central Region for management purposes, these data do not provide enough detail to determine the breeding population of origin of birds recovered on stopover and wintering areas. To obtain more fine-scale data, we undertook a phylogeographic study of American Woodcock populations throughout their primary breeding range in the eastern United States and Canada using mitochondrial DNA (mtDNA) sequences from the hypervariable control region I (CRI) and ND6 gene. Despite high haplotype diversity, nucleotide diversity was low and there was no phylogeographic structure among American Woodcock populations across the species range, with birds from many states and provinces in both management regions sharing identical haplotypes. Results suggest recent or ongoing gene flow among populations, with asymmetric movement of birds between migration flyways. As has been demonstrated for several other avian species in North America, American Woodcock appear to have undergone a rapid population expansion following the late Pleistocene glacial retreat. Thus, a combination of historical demographic factors and recent or ongoing gene flow mask any population structure based on mtDNA that might accrue from philopatry to breeding areas observed in studies of marked birds.

Phylogéographie de Scolopax minor: Est-ce que les Unités de Gestion Basées sur les Données de Retour de Bagues Reflètent les Unités de Gestion Basées sur la Génétique?
No Evidence for Adaptive Differential Sex Allocation in Red Junglefowl (Gallus Gallus)
Authors: Parker Timothy H.
Published: September 2019

In many situations, selection should favor females that bias the sex ratio of their offspring. Two commonly examined factors potentially influencing off- spring sex ratio are paternal ornamentation and maternal condition. Male junglefowl with larger combs are attractive to females. I housed female Red Junglefowl (Gallus gallus) with sterile male consorts and artificially inseminated them with sperm from other males that the females never saw. I found no relationship between either the comb size of the consort or the comb size of the sperm donor and the sex ratio of the offspring. I previously reported a significant sex ratio bias related to maternal mass in Red Junglefowl. However, that analysis was based on sex ratio data not weighted for brood size and assuming a normal distribution. Here, I show that this effect disappears when I conduct a more appropriate analysis weighting sex ratio according to brood size and accounting for the binomial error distribution. I also failed to find evidence that male chicks hatch from larger eggs than female chicks. These results suggest that Red Junglefowl females may not bias the sex ratio of their brood in response to either their own condition or the attractiveness of the males with whom they copulate. Furthermore, these results demonstrate the importance of choosing the correct methods of sex ratio analysis.

Falta de Evidencia de Asignación Adaptativa Diferencial entre Sexos en Gallus gallus
Boluses: An Effective Method for Assessing the Proportions of Cephalopods in the Diet of Albatrosses
Authors: Xavier José C. , Croxall John P. , Cresswell Kate A.
Published: September 2019

The method of collecting and analyzing boluses to characterize the cephalopod diet of albatrosses has been used in many diet studies. However, no study has validated this method. We compared boluses and stomach samples from Gray-headed Albatrosses (Thalassarche chrysostoma) and Black-browed Albatrosses (T. melanophris) to (1) study the consumption and diversity of cephalopods in these species, (2) investigate biases associated with each sampling method, and (3) estimate the number of samples needed to characterize these albatross’s cephalopod diet. We found that collection and analysis of boluses is a simple, efficient, and noninvasive method for assessing the cephalopod diet of these albatross species, but it is inadequate for characterizing the more easily digestible dietary components, such as fish and crustaceans. Both boluses and stomach samples showed that the two albatross species fed on cephalopods of similar sizes and from the same families (Ommastrephidae, Onychoteuthidae, and Cranchiidae). Furthermore, the main prey species (Martialia hyadesi, Kondakovia longimana, and Galiteuthis glacialis) and the total number of cephalopod species consumed (18–24 species) were the same for both albatrosses. To include all cephalopod species, using a sample-randomization technique, a minimum of 61 and 43 boluses were needed for Gray-headed and Black- browed albatrosses, respectively; but to adequately describe the diversity and size frequency of the main prey species, 82 and 371 boluses would be needed.

Les Pelotes de Réjection: Une Méthode Efficace pour Évaluer la Proportion de Céphalopodes dans le Régime Alimentaire chez les Albatros
Population Genetics of the Galápagos Hawk (Buteo Galapagoensis): Genetic Monomorphism Within Isolated Populations
Authors: Bollmer Jennifer L. , Whiteman Noah K. , Cannon Michelle D. , Bednarz James C. , Vries Tjitte de , Parker Patricia G.
Published: September 2019

Because of their smaller size and isolation, island populations tend to be more divergent and less genetically variable than mainland populations. We collected DNA samples from nine Galápagos Hawk (Buteo galapagoensis) island populations, covering the species’ entire range. Neutral minisatellite DNA markers were used to calculate within-island genetic diversity and between-island genetic differentiation (FST). Typically, these markers mutate too quickly to be informative in such studies. However, in very small, isolated populations, concerns about high mutational rate are obviated by the relative force of genetic drift. Individuals within islands had the highest levels of reported genetic uniformity of any natural bird population, with mean within-population band-sharing similarity values ranging from 0.693 to 0.956, increasing with decreasing island size. Galápagos Hawks exhibit cooperative polyandry to varying degrees across islands; however, we did not find an association between degree of polyandry and genetic variability. Between-island FST values ranged from 0.017 to 0.896, with an overall archipelago value of 0.538; thus, most populations were genetically distinct. Also, we documented higher levels of genetic similarity between nearby populations. Our results indicated negligible gene flow among most Galápagos Hawk populations, and genetic drift has played a strong role in determining structure at these minisatellite loci.

Genética de Poblaciones de Buteo galapagoensis: Monomorfismo Genético dentro de Poblaciones Aisladas
Phylogenetic Relationships of the Madagascar Pygmy Kingfisher (Ispidina Madagascariensis)
Authors: Marks Ben D. , Willard David E.
Published: September 2019

The avifauna of Madagascar presents a complicated taxonomic and biogeographic problem. Although Madagascar was once connected to Africa, the birds of the island are not all of African origin. The Madagascar Pygmy Kingfisher (Ispidina madagascariensis) is sometimes placed in the African genus Ispidina and sometimes in the Southeast Asian genus Ceyx. We sequenced 755 base pairs of mitochondrial DNA from a fragment of the NADH dehydrogenase subunit II (ND2) and from the complete NADH dehydrogenase subunit III (ND3). We used these data to construct phylogenetic hypotheses for the Alcedinidae. Using these phylogenies, we evaluate previous hypotheses of relationships of I. madagascariensis. Although we cannot reject the hypothesis that I. madagascariensis is indeed a member of Ispidina, tree-building analyses support a relationship not with Ispidina or Ceyx, but instead with members of the African genus Corythornis. These data suggest that certain behaviors and plumage types have evolved several times in the Alcedinidae.

Relations Phylogénétiques de Ispidina madagascariensis
Massachusetts Breeding Bird Atlas
Authors: Robbins Chandler S.
Published: September 2019

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.
Tracking Ocean Wanderers: The Global Distribution of Albatrosses and Petrels
Authors: Veit Richard R.
Published: September 2019

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.
Diet Influences Life Span in Parrots (Psittaciformes)
Authors: Munshi-South Jason , Wilkinson Gerald S.
Published: September 2019

Evolutionary hypotheses regarding longevity predict that life span should increase as extrinsic mortality rates decrease. Specifically, a decline in age-specific survival and fertility should evolve and decrease life span in proportion to the magnitude of the mortality risk. We examined these ideas using a new data set on maximum longevity, ecology, and life history of 162 parrot species (Psittaciformes). Parrots are generally long-lived but exhibit remarkable variation in life span between similar-sized genera, with particularly long-lived species occurring in the Cacatua, Calyptorhynchus, and Amazona. After controlling for both body size and phylogenetic ancestry using a phylogenetic supertree of all 352 parrot species, type of diet and communal roosting explain significant variation in parrot life span, but the influence of communal roosting is statistically dependent on an association with diet type. We suggest that extreme longevity in parrots has evolved in response to species-specific characteristics of diet, habitat, and behavior that influence extrinsic mortality rates.

La Dieta Influencia la Longevidad en los Psittaciformes
Nests Without Eggs: Abandonment or Cryptic Predation?
Authors: Maddox J. Dylan , Weatherhead Patrick J.
Published: September 2019

We determined whether nests that did not receive eggs was attributable to cryptic nest predation (i.e. predation of eggs laid between nest checks) or nest abandonment in Common Grackles (Quiscalus quiscula). Nest predation was extremely low (∼2%), whereas more than 44% of 427 nests found during nest building never received an egg; this indicates that nest abandonment accounted for most nests without eggs. Nest construction was completed for 32% of nests that were abandoned. Few nests known to have received eggs were abandoned. As the breeding season progressed, both nest abandonment and time from nest completion to first egg decreased. It has been proposed that the delay in egg laying early in the season allows females to optimize timing of egg laying. Nest abandonment may also serve this purpose, but seems an unnecessarily expensive mechanism. Alternatively, nest abandonment could be involved with mate switching. Understanding why nests are abandoned requires data on the associated ecological circumstances, in addition to accurate identification of instances of abandonment. The latter requires distinguishing abandonment from cryptic predation. Rates of nest abandonment can be estimated for populations by using rates of known nest predation during egg laying. For individual nests, however, distinguishing abandonment from cryptic predation requires detailed observation (e.g. video cameras), except in circumstances such as ours, where predation is extremely low.

Nidos sin Huevos:?Abandono o Depredación Críptica?
Are Multiple Infections More Severe for Purple Martins (Progne Subis) Than Single Infections?
Authors: Davidar Priya , Morton Eugene S.
Published: September 2019

Between 1986 and 1993, we studied a breeding colony of Purple Martins (Progne subis) in Maryland that were chronically infected with two blood parasites: Haemoproteus prognei, a haematozoan, and an unidentified filarial nematode. We assessed whether cross-infections are more severe than single infections by comparing the return rates of birds infected with either or both parasites and the return rates of uninfected controls. Birds were captured every year and banded, and blood smears were taken for parasite screening. Average prevalence of filaria among the 400 birds screened during this period was 22%. Birds usually became infected by their second year (SY), and infected SY birds had significantly lower return rates than older birds. Cross-infections were rare (8%) and were fatal in 90% of cases. With one exception, birds infected with H. prognei acquired filaria as a second infection, which suggests that although both blood parasites are relatively benign for older Purple Martins, co-infection with a second parasite (in this case, H. prognei) almost always results in death.

Est-ce que les Infections Multiples Sont Plus Sévères que les Infections Simples chez Progne subis?
Stability of Pentosidine Concentrations in Museum Study Skins
Authors: Fallon Jesse A. , Radke William J. , Klandorf Hillar
Published: September 2019

Accumulation of the advanced glycation endproduct pentosidine (Ps) in skin collagen is strongly correlated with age of adult birds. This allows age estimates to be made without use of banding data. We examined the stability of Ps in museum study skins. We took skin samples from six Ruffed Grouse (Bonasa umbellus) study skins at three-month intervals over the course of one year. The data revealed no significant variation in Ps concentrations within individual birds, which indicates that Ps is stable in study skins for at least 12 months. These data suggest that inferences concerning age might be made from similarly prepared specimens from collections around the world. Additionally, we found significant variations in Ps concentrations in skin collagen among six different locations on the study skins. This suggests that care and consistency are important when excising skin for Ps measurement and age estimation in birds.

Estabilidad de las Concentraciones de Pentosidina en Pieles de Estudio de Museo
Is Melanin a Defense Against Feather-Feeding Lice?
Authors: Bush Sarah E. , Kim Dukgun , Moyer Brett R. , Lever Jackson , Clayton Dale H.
Published: September 2019

The adaptive basis of plumage color has received much attention, including the finding that color can reveal information about parasite loads to potential mates. A related possibility, that color may be a direct defense against parasites, has received less attention. Melanin makes feathers tough and more resistant to wear and tear. Melanin may also make feathers more difficult for feather-feeding parasites to eat. We explored the role of melanin as a possible ectoparasite defense using Rock Pigeons (Columba livia) and their feather-feeding lice (Insecta: Phthiraptera). Rock Pigeons are an ideal species for such work because of the extreme variation in the feathers of different color morphs, ranging from melanin-rich black to melanin-free white individuals. We tested the effect of melanin on lice in several ways. First, we compared the natural louse loads of free-ranging pigeons to see whether the more melanistic color morphs had fewer lice. We also did laboratory assays in which we measured the survival and reproductive success of pigeon lice forced to feed on feathers with different amounts of melanin, and we compared the quantities of feather material consumed by these lice. Finally, we tested the habitat and feeding preferences of lice exposed to feathers with different amounts of melanin. None of our tests revealed any effect of melanin on lice. We conclude that melanin is not, at least in Rock Pigeons, a defense against feather lice.

¿Es la Melanina una Defensa Contra los Piojos que se Alimentan de Plumas?