bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subspecific and Temporal Variation in the Structurally Based Coloration of the Ultramarine Grosbeak
Authors: Barreira Ana S. , Lijtmaer Dario A. , Lougheed Stephen C. , Tubaro Pablo L. 
Published: September 2019

AbstractAbstractUltramarine Grosbeaks (Cyanocompsa brissonii) possess a striking sexual dichromatism, with males dark blue and females brown. There are two subspecies in Argentina: the larger-bodied C. b. argentina, which is common in shrubs and semiopen areas, and the smaller C. b. sterea that inhabits forests. We measured reflectance spectra of six plumage patches from study skins to evaluate the possibility of color differences between males of each subspecies and temporal variation in plumage coloration. We found differences between subspecies in color brightness, hue, saturation, and UV chroma in the plumage patches of more conspicuous coloration, which could be related to ambient light differences between the environments that each subspecies inhabits. We also documented temporal color variation in some plumage patches, in particular a gradual decrease of UV reflectance and a gradual increase in hue after molting, possibly attributable to feather wear.
Potential Ecotoxicological Significance of Elevated Concentrations of Strontium in Eggshells of Passerine Birds
Authors: Mora Miguel A. , Taylor Robert J. , Brattin Bryan L. 
Published: September 2019

Abstract

Abstract
We investigated the occurrence and potential ecotoxicological significance of elevated concentrations of strontium (Sr) in eggshells of nine passerine birds from four regions in Arizona. Concentrations of Sr in eggshells ranged from 70 to 1360 µg g−1 dry weight (overall mean  =  684 ± 345 SD µg g−1 dw) for the four regions. 23% of the eggshells had Sr concentrations greater than 1000 µg g−1 dw. To our knowledge, these are among the highest levels of Sr that have been reported in bird eggshells in North America. Of the nine species, Brown-headed Cowbirds (Molothrus ater) had the greatest concentrations of Sr. There was a significant positive correlation between Sr and calcium (Ca), and between barium (Ba) and Ca. Ca, Sr, and Ba interact with each other and can exert similar chemical and pharmacological effects. Mean (n ≥ 3) eggshell:egg ratios for Sr varied with species and ranged from 6.1:1 to 40.2:1; ratios for individual eggs reached 92.7:1. Mean Sr/Ca values ranged from 1.3 × 10−3 to 3.0 × 10−3 and mean eggshell thickness ranged from 83 ± 6 to 120 ± 9 µm for all species. Eggshell thickness was not significantly correlated with Sr for any species but tended to increase with Sr concentrations. We postulate that high concentrations of Sr in the shell could affect later-stage embryos by possible interference with Ca metabolism and bone growth, resulting in reduced hatching success and potential minor beak deformities.
Foraging Behaviors of Surf Scoters and White-Winged Scoters During Spawning of Pacific Herring
Authors: Lewis Tyler L. , Esler Daniel , Sean Boyd W. 
Published: September 2019

Abstract

Abstract
Winter diets of Surf (Melanitta perspicillata) and White-winged Scoters (M. fusca) are composed primarily of bivalves. During spawning of Pacific herring (Clupea pallasi) in early spring, scoters shift their diets to herring eggs. Using radio-telemetry, we contrasted scoter foraging behaviors between winter and herring spawning periods. Scoters increased their dive durations during herring spawning, likely to maximize the amount of roe consumed per dive; in winter, dives were typically terminated upon clam capture. Scoters spent approximately 50% less time foraging (min underwater hr−1) and decreased their dive rate (dives hr−1) by 70% when feeding on roe. The observed reduction in time spent foraging was presumably caused by the abundance of herring eggs, and thus a reduction in prey search-time. Scoters were able to meet energetic requirements with reduced effort, despite potentially increased demands related to spring fattening. Less time spent foraging may also allow more time for premigratory courtship behaviors.
Sound Transmission and Song Divergence: A Comparison of Urban and Forest Acoustics
Authors: Slabbekoorn Hans , Yeh Pamela , Hunt Kimberly 
Published: September 2019

AbstractAbstractDegradation of acoustic signals during transmission presents a challenging selection pressure for animals dependent on vocal communication. Sound transmission properties differ among habitats and may drive the evolution of vocal signals in different directions. Urban habitat is expanding worldwide and an increasing number of species, including many birds, must now communicate around buildings and over concrete. Urban habitats are evolutionarily new, although to some extent they may acoustically resemble rocky habitat such as cliffs and canyons. Neither urban nor these natural habitats have been studied in any detail for the selection pressure they may exert on animal communication. Dark-eyed Juncos (Junco hyemalis) commonly inhabit montane pine forests across North America, but for about 25 years an isolated population has been successfully breeding in an urban environment in southern California. We investigated potentially divergent selection pressures on junco songs, using sound transmission experiments with artificial sound stimuli, in natural forest habitat and in this urban habitat. Transmission properties differed significantly, resulting in tails of reflected sound with gradually declining amplitude in the forest and in multiple discrete echoes in the urban environment. We expected environmental selection in urban habitat to favor shorter songs with higher frequencies and slower trill rates. Despite the presence of relatively short urban songs, there was no significant shortening overall. There were also no differences in trill rates, but we did find a significantly higher minimum frequency in the urban junco population compared to three of four forest populations. Although the pattern of song divergence was not consistent and it is difficult to draw firm conclusions from this single urban population, our transmission results suggest that echoes could be important in shaping urban birdsong.
Habitat, Dominance, and the Phenotypic Quality of Male Black-Capped Chickadees
Authors: van OORT Harry , Otter Kenneth A , Fort Kevin T , McDONELL Zoe 
Published: September 2019

AbstractAbstractThe provisioning of offspring is limited by resource abundance and is therefore likely to vary with habitat quality and the ability of parents to obtain food. Provisioning effort may also vary because males choose different life-history strategies depending on their rank and environment. Socially dominant males have higher costs of self-maintenance compared with subordinates, yet this is likely compensated for by their priority access to resources. It is unclear, however, whether this translates into benefits for females through male provisioning effort, and how this might vary with habitat suitability. We assessed patterns of body condition, blood hematocrit levels, and provisioning effort of dominant and subordinate male Black-capped Chickadees (Poecile atricapillus) breeding in two habitats known to differ in quality. Within ranks, males were similar in size and condition across habitats. Dominant males were not structurally larger than subordinates, but they were in better condition than subordinates in both habitats. There was an additive effect of habitat and dominance rank on hematocrit level; dominant males had higher hematocrit levels than subordinates regardless of habitat, and all males breeding in poor habitat had elevated hematocrits. A habitat-rank interaction revealed a greater disparity in provisioning rates among dominant and subordinate males in poor habitats. These results suggest that dominant males may be particularly good mates when resources are scarce.
Neotropical Forest Bird Communities: A Comparison of Species Richness and Composition at Local and Regional Scales
Authors: Blake John G. 
Published: September 2019

Abstract
Species richness and composition of Neotropical forest bird communities vary spatially at both large and small scales, but previous comparisons based on 100 ha plots have not replicated plots within a region. I sampled birds in two 100 ha plots in lowland forest of eastern Ecuador to better understand how species richness and composition vary over smaller spatial scales. Birds were sampled in February and April of 2002–2005 (only in February in 2005). Plots were approximately 1.5 km apart in predominantly terra firme forest. A total of 319 species (285 and 281 per plot) from 43 families were represented in ~16 000 detections per plot; number of species and detections per sample averaged approximately 185 and 2300, respectively. Numbers of species and detections per family were strikingly similar in the two plots, but numbers of detections of individual species often differed, likely in response to differences in habitat between the two plots. Species richness and composition were similar in many respects to comparable data from Ecuador, Peru, and French Guiana, but differed from those of Panama. Differences were most pronounced at the species level, less at the genus level, and least when comparisons were based on families. Differences among sites in South America were correlated with geographic distance at the species and genus levels, but not at the family level. Results illustrate the value of replicated plots within a region for understanding how species richness and composition can vary at small spatial scales, and highlight the importance of beta diversity for determining overall patterns of regional diversity.
Estimating Origins of Three Species of Neotropical Migrant Songbirds at a Gulf Coast Stopover Site: Combining Stable Isotope and Gis Tools
Authors: Hobson Keith A. , Van Wilgenburg Steve , Wassenaar Leonard I. , Moore Frank , Farrington Jeffrey 
Published: September 2019

AbstractMeasurement of stable-hydrogen isotopes (δD) in feathers of migrating birds can provide information on where feathers were grown in North America, at least to an approximate band of latitude. This approach has greatly increased our ability to investigate aspects of avian migration and stopover ecology, since origins of unmarked individuals at migration stopover sites can be estimated for the first time. However, few studies have explored the power of combining isotope measurements with geographic information system (GIS) methods. We measured δD values in feathers of hatching-year (HY) Swainson's Thrushes (Catharus ustulatus; n  =  60), Wood Thrushes (Hylocichla mustelina; n  =  113), and Gray Catbirds (Dumetella carolinensis; n  =  158) at Ft. Morgan Peninsula, Alabama (30°10′N, 88°00′W), a migration stopover site along the Gulf coast. By applying an elevation-corrected hydrogen isotope basemap for birds in North America, we derived a GIS surface depicting expected feather δD values across the continent. We then used GIS to constrain the possible origins of the sampled populations by considering only values falling within the North American breeding ranges of the species. We depicted likely origins of migrating birds by the 50% and 75% tolerance limits of the data. Our GIS analysis indicated that our captured populations represented much-reduced regions of possible origin based on the North American breeding distributions. Gradients in abundance data from the North American Breeding Bird Survey (BBS) allowed us to further narrow possible origins within isotopic boundaries for Wood Thrushes and Gray Catbirds. This exercise provided a means by which priority regions and habitats could be assessed at large continental scales based on actual productivity. We suggest the combination of isotopic and GIS tools provides a powerful means to derive conservation priorities and to investigate key factors involved in the ecology of avian migration and stopover.
Seasonal Distribution, Abundance, and Nesting of Puna, Andean, and Chilean Flamingos
Authors: Caziani Sandra M. , Rocha Olivio Omar , Rodríguez Ramírez Eduardo. , Romano Marcelo , Derlindati Enrique J. , TÁLAMO Andrés , Ricalde David , Quiroga Carmen , Pablo Contreras Juan , Valqui Mariana , Sosa Heber 
Published: September 2019

Abstract
Of the world's five flamingo species, the rarest and least known are the Puna Flamingo (Phoenicoparrus jamesi) and the Andean Flamingo (P. andinus). These two species coexist with the more common Chilean Flamingo (Phoenicopterus chilensis) throughout much of their range. We conducted four simultaneous surveys from 1997 to 2001 (two in summer and two in winter) to estimate the distribution and abundance of all three species in Argentina, Bolivia, Chile, and Peru, at a regional scale. Of 224 wetlands surveyed, 179 had flamingos; 63% of these were in the high Andes (above 4000 m), 25% were in the puna (3000 to 4000 m), and the remainder were in lowlands (below 3000 m). Maximum counts were 64 000 Puna Flamingos (summer 1998), 34 000 Andean Flamingos (summer 1997), and 83 000 Chilean Flamingos (winter 1998). In summer, Puna Flamingos congregated at wetlands in the high Andes, with 50% of the population in just three lakes: Colorada, Grande, and Vilama. Andean Flamingos were more uniformly distributed across a broader elevational range (2500 m), and Chilean Flamingos showed a heterogeneous distribution pattern. In winter, all species moved to lower latitudes within the high Andes and to lower altitudes on the central plains of Argentina. The most important nesting wetlands were Colorada, in Bolivia, for the Puna Flamingo, Surire and Atacama, in Chile, for the Andean Flamingo, and Surire for the Chilean Flamingo. We recommend continued monitoring through simultaneous summer surveys, and a conservation strategy that considers the large spatial and temporal scales at which these species operate, including their seasonal migrations.
Effects of Distance to Edge and Edge Type on Nestling Growth and Nest Survival in the Wood Thrush
Authors: Kaiser Sara A. , Lindell Catherine A. 
Published: September 2019

Abstract
Many studies investigating edge effects on forest-nesting birds have focused on nest success. Fewer have examined edge effects on other components of fitness. Nestling growth rates have been positively correlated with food availability, which may differ at edges compared to the forest interior. However, previous work has not examined growth as a function of distance to edge and edge type. We investigated whether edge type, distance to edge, hatching date, brood size, brood parasitism, year, and site influenced growth rates of wings, tarsi, and mass of nestling Wood Thrushes (Hylocichla mustelina) using regression tree analyses. Simultaneously, we examined edge effects on daily nest survival. We conducted our study in southwestern Michigan in 2002 and 2003. We located 175 nests and measured nestlings from 61 nests. Contrary to expectations, tarsal and mass growth rates were more rapid near edges than in the forest interior and tarsal growth rates were more rapid near gradual edge types than near abrupt edge types. Wing chord growth rates were more rapid in the forest interior than at edges. Mass and tarsal growth rates were more rapid later in the breeding season, when brood sizes were smaller. We found no effect of edge type or distance to edge on nest survival. The influence of edge on nestling growth rate but not nest survival suggests nestling growth rates may indicate edge-interior and edge type differences in habitat quality, even when high regional fragmentation levels overwhelm potential edge-interior differences in nest survival.
Mass Loss by Breeding Female Songbirds: Food Supplementation Supports Energetic Stress Hypothesis in Black-Throated Blue Warblers
Authors: Nagy Laura R. , Stanculescu Dominic , Holmes Richard T. 
Published: September 2019

Abstract
Reproduction is physiologically stressful for many animals. Female birds often lose body mass after their young hatch, which has been commonly attributed either to an energetic deficit incurred while breeding (the energetic stress hypothesis) or to an adaptive reduction in wing-loading to save energy during flight (the wing-loading hypothesis). We tested these two hypotheses for an open-cup nesting passerine, the Black-throated Blue Warbler (Dendroica caerulescens), using a food-supplementation experiment. We found that females provided with extra food lost less body mass between the incubation and nestling periods than did control females and that mass loss varied seasonally, with females in both treatments that nested earlier in the season losing more mass. We conclude that greater mass loss in control females supports the energetic stress hypothesis in Black-throated Blue Warblers.
Breeding Biology of Passerines in a Subtropical Montane Forest in Northwestern Argentina
Authors: Auer Sonya K. , Bassar Ronald D. , Fontaine Joseph J. , Martin Thomas E. 
Published: September 2019

Abstract
The breeding ecology of south temperate bird species is less widely known than that of north temperate species, yet because they comprise a large portion of the world's avian diversity, knowledge of their breeding ecology can contribute to a more comprehensive understanding of the geographic diversity of avian reproductive traits and life history strategies. We provide the first detailed examination of the reproductive strategies of 18 forest passerines of subtropical, northwestern Argentina. Mean clutch sizes were smaller and egg mass was greater than for north temperate birds, but differed among species and nest types, with cavity-nesters having larger clutches than species with open-cup and enclosed nests. Across all species, the average breeding season duration was 50 days; thus, the common perception that southern species have smaller clutch sizes because of longer breeding seasons is not supported in this community. Daily nest predation rates were influenced by nest type, cavity nests suffering the least from predation, as found in north temperate systems. Only females incubated eggs in all but one species, whereas both parents fed and cared for nestlings in all species. Mean nest attentiveness was low compared to north temperate passerines. Mean hourly nestling feeding rates differed among species and were negatively related to nest predation risk. In short, coexisting species in this subtropical forest varied in their life history strategies, in part correlated with variation in nest predation risk, but also differing from north temperate species.
Late Summer and Fall Nesting in the Acorn Woodpecker and Other North American Terrestrial Birds
Authors: Koenig Walter D. , Stahl Justyn T. 
Published: September 2019

AbstractAcorn Woodpeckers (Melanerpes formicivorus) at Hastings Reservation in central coastal California exhibit a bimodal peak in annual breeding activity. One peak occurs in spring during which the majority of breeding takes place, while a second is centered in late August as the new acorn crop matures. These latter nests are mostly initiated in late summer but often do not fledge until at least late September and are thus referred to here as ‘fall’ nests. Fall nests occur in about one-third of all years, taking place when the acorn crop is large and summer temperatures are relatively high. Fledglings from fall nests constitute 4.3% of the population's total productivity and survive and recruit to the population at levels comparable to spring fledglings. Fall nesting is less likely in groups in which either the male or female breeding adults have undergone a change from the prior year, but groups are otherwise indistinguishable. Ecologically, fall nesting is closely tied to the acorn crop and thus to breeding success in the following, rather than the prior, spring. Among North American terrestrial birds in general, fall breeding has been reported in 16% of all species and is significantly more common among residents and colonially nesting species, in which the frequency exceeds 25%. Furthermore, fall nesting is likely to have been underreported in the literature. Thus, this phenomenon is at least an irregular part of the breeding biology of a substantial fraction of North American birds and should be considered a possibility in population studies of temperate-zone species. This is especially true given that fall nesting is likely to increase as global warming takes place.
Feeding Ecology of Greater Snow Goose Goslings in Mesic Tundra on Bylot Island, Nunavut, Canada
Authors: Audet Benoît , Gauthier Gilles , LÉVESQUE Esther 
Published: September 2019

AbstractAlthough mesic tundra is a habitat commonly used by arctic-nesting geese, their feeding ecology in this habitat is little known compared to wetlands. Our objectives were to determine the diet and food selection of Greater Snow Goose (Chen caerulescens atlantica) goslings in relation to the nutritional quality of plants growing in mesic tundra habitats on Bylot Island, Nunavut, Canada. We used two different but complementary approaches: examination of esophageal contents of sacrificed wild goslings, and direct observation of the feeding activity of captive, human-imprinted goslings. The latter method was innovative and provided a reliable description of the diet, with results comparable to those obtained from wild goslings. Although mesic habitats have a more diverse floristic composition than wetlands and sparse graminoid cover, Gramineae were preferentially selected and dominated the diet (~50%). The rest of the diet consisted mainly of members of the Juncaceae, Polygonaceae, and Leguminosae families. The diet of very young goslings was diverse, but as they aged and gained efficiency, they concentrated on a few taxa. Goslings ate mostly leaves (~80%), but flowers (~20%) were also important. Food selection was influenced by nitrogen and total phenolic compounds content of plants, but the ratio of phenolic compounds to nitrogen in plant organs was most determinative of food choice. Neutral detergent fiber content of plants did not influence plant selection. Both plant nutritional quality and availability determined gosling diet across different mesic habitats and growing goslings appeared to maximize their intake of metabolizable proteins.
Nest Survival Patterns in Willow Ptarmigan: Influence of Time, Nesting Stage, and Female Characteristics
Authors: Wilson Scott , Martin Kathy , Hannon Susan J. 
Published: September 2019

Abstract
Nest predation is the most important factor limiting reproductive success of Willow Ptarmigan (Lagopus lagopus), as it is for many bird species. Using program MARK, we examined patterns of daily nest survival in two widely separated populations of Willow Ptarmigan in Manitoba and British Columbia, Canada, by examining variation among years, over the course of the breeding season or in relation to the age of the nest, or age and condition of the female. At La Pérouse Bay, Manitoba, daily nest survival increased linearly throughout the season, with moderate annual variation. Nests also had higher daily survival during laying and late in incubation, and lower survival early in incubation. At Chilkat Pass, British Columbia, daily nest survival varied strongly by year and nests had higher survival early and late in the season, but survival was not affected by the age of the nest. At both sites, but especially at Chilkat Pass, periods of lower nest survival tended to coincide with peak breeding periods, suggesting predators may adjust their search effort based on the likelihood of locating nests. Neither female age nor condition were included in the best models. Thus, in both ptarmigan populations, nest survival patterns appeared to be influenced more by ecological factors than by individual characteristics of breeding females. The extent of annual variation and seasonal patterns may have differed between sites due to the different predator and alternative prey communities.