bluuebunny/crossref_metadata_2025_split huggingface dataset:
Richness and Composition of Oasis Bird Communities: Spatial Issues and Species–Area Relationships
Authors: Selmi Slaheddine , Boulinier Thierry , Barbault Robert 
Published: September 2019

AbstractWe used data on breeding bird communities of the oases of southern Tunisia to investigate variation in species richness and composition among local communities in relation to spatial configuration of the oasis system and to assess significance of the relationship between oasis size and local richness. Oases could be grouped into three regional systems, namely littoral, saharan, and mountainous oases. We found that at the scale of the entire oasis system, species richness and species composition exhibited significant spatial autocorrelation. That result was consistent with our prediction that the particular spatial organization of oases may have led to regional differences in availability of potential colonizers and that higher species exchange within oasis zones than among oasis zones may have played an important role in shaping local communities. With regard to the species–area relationship, we thus found that a model accounting for spatial covariance was more parsimonious than a standard regression model not incorporating information on the spatial location of oases. Overall, oasis size was a good predictor of species richness, but results were sensitive to spatial scale at which the relationship was examined. Aside from oceanic islands and forest patches, oases may constitute interesting systems to study how regional processes affect local diversity.
Reproduction and Survival in a Variable Environment: Ural Owls (Strix Uralensis) and the Three-Year Vole Cycle
Authors: Brommer Jon E. , Pietiäinen Hannu , Kolunen Heikki 
Published: September 2019

Abstract
We analyzed data on 535 Ural Owl (Strix uralensis) breeding attempts and consecutive survival of both adults and offspring from 1987–1998 in relation to the regional abundance of the Ural Owl's main prey, voles, which show a cycle of low, increase, and peak phases in their population numbers. Vole abundance varied up to 49×, crashing during spring–summer every three years. The breeding population tracked abundance of voles in the previous autumn with respect to percentage of pairs breeding and their reproductive output (laying date, clutch size), largely irrespective of phase. Survival depended on vole density in the preceding autumn, but was generally highest in the increase phase. There was thus a paradoxical situation in the peak phases, when vole populations crashed; the owls produced large clutches, but those survived poorly. Some adaptive and nonadaptive scenarios of the Ural Owl's life history are discussed.
Validation of the Labeled-Water Method for Estimating Food Consumption in Nestling Herons
Authors: Salatas Johanna H. , Frederick Peter C. , Nagy Kenneth A. , Williams Gary E. 
Published: September 2019

AbstractAccurate measurements of food consumption by young birds are of great value in a variety of ecological studies, but traditional measurement methods are problematic and prone to high error. In animals that obtain their water primarily through food, it is possible to estimate food consumption from measurements of water influx rate, using radioactively labeled water (3H2O), and diet water content. We evaluated that method by comparing actual food consumption with simultaneous estimates of food consumption based on the labeled-water method in captive-reared nestling Tricolored Herons (Egretta tricolor). There was good agreement. The average error in the isotope method was −2% (SD = 8%), and that difference was not statistically significant. An errors analysis indicated that the accuracy of this method is sensitive to determinations of dietary water content and animal body water content, and to estimates of rates of metabolic water production and unidirectional water vapor input.
Does Egg Rejection Account for the Low Incidence of Cowbird Parasitism in Chestnut-Collared Longspurs (Calcarius Ornatus)?
Authors: Davis S. K. , Klippenstine D. R. , Brigham R. M. 
Published: September 2019

AbstractWe experimentally parasitized Chestnut-collared Longspur (Calcarius ornatus) nests with mimetic and nonmimetic Brown-headed Cowbird (Molothrus ater) eggs to determine whether the low frequency of parasitism reported for that grassland host is due to egg rejection behavior. Longspurs accepted all 23 mimetic eggs (real and wooden) and rejected 9 of 22 blue nonmimetic eggs. Our results suggest longspurs accept cowbird eggs even though they are physically capable of ejecting them from their nest. Thus, the low parasitism frequency reported for that species is not a result of egg rejection behavior, but may be due to antiparasite strategies that reduce their chances of being parasitized (e.g. nest defense behavior).
Primary Sex-Ratio Variation in Two Brood Parasitic Birds: Brown-Headed Cowbird (Molothrus Ater) and Common Cuckoo (Cuculus Canorus)
Authors: Kasumovic Michael M. , Gibbs H. Lisle , Woolfenden Bonnie E. , Sealy Spencer G. , Nakamura Hiroshi 
Published: September 2019

Abstract
We examined primary sex-ratios of two brood parasitic species, Brown-headed Cowbird (Molothrus ater) and the Common Cuckoo (Cuculus canorus), to determine whether there was any evidence of primary sex-ratio manipulation as has been demonstrated in other species of birds. Despite good reasons for why female brood parasites should manipulate the primary sex-ratio of their young, we found a lack of evidence for a bias in the sex-ratio of eggs produced at the population level, with respect to the host species parasitized or time of breeding season, or in terms of the sex ratio of eggs produced by individual females. Thus, this study provides another example in birds of little evidence for sex-ratio variation in relation to environmental factors.
Male Wing-Patch Asymmetry and Aggressive Response to Intruders in the Common Chaffinch (Fringilla Coelebs)
Authors: Jaboński Piotr G. , Matyjasiak Piotr 
Published: September 2019

AbstractRecent studies reveal that asymmetries of bilateral characteristics may reflect poor condition, serving as an honest indicator of mate quality. We asked whether bilateral asymmetry might also influence behavior during aggressive intrasexual contests. In the Common Chaffinch (Fringilla coelebs), bilateral, white wing patches (epaulettes) are used during aggressive interactions. We recorded responses of males to model intruders placed on territories of focal males, to determine whether their response to asymmetry varied with wing-patch size. When epaulettes were large, models with asymmetric patches elicited more rapid, directed aggression from the territory owners than did models with symmetric patches. We observed no such difference when model intruders had small epaulettes. If asymmetry of epaulettes in chaffinch males indicates poor condition, our results suggest higher costs of aggressive signaling for individuals in poor than good condition.
Subspecific Differentiation and Conservation of Song Sparrows (Melospiza Melodia) in the San Francisco Bay Region Inferred by Microsatellite Loci Analysis
Authors: Chan Yvonne , Arcese Peter 
Published: September 2019

AbstractWe examined genetic population structure of five putative subspecies of Song Sparrows (Melospiza melodia) in the San Francisco Bay region (M. m. samuelis, M. m. maxillaris, M. m. pusillula, M. m. gouldii, and M. m. heermanni) at nine microsatellite loci to assist the development of Song Sparrow conservation and management strategies. We sampled nine populations from five putative subspecies and found low estimates of differentiation between populations within subspecies and between. Despite low estimates of divergence, genetic structure at the subspecies level was indicated by the larger amount of variance accounted for by subspecies than populations. We propose that a management unit encompassing the range of M. m. pusillula be given priority for conservation on the basis of the extent of genetic divergence shown by Cavalli-Sforza and Edward's chord distance, and the topology of an unweighted pair group cluster analysis supported by 100% of bootstrap replicates across loci. Although M. m. samuelis and M. m. maxillaris appear undifferentiated from M. m. heermanni, it remains possible that adaptive differences between those types were not identified with neutral loci.
Effects of Thinning and Herbicide Treatments on Nest-Site Selection by Songbirds in Young Managed Forests
Authors: Easton Wendy E. , Martin Kathy 
Published: September 2019

AbstractRoutine silvicultural practices continue to alter the structure and composition of forests after logging by removing deciduous vegetation from regenerating coniferous forests. We identified nest trees and surveyed vegetation in a 5 m radius surrounding songbird nests (nest patch) and compared the nest patches to available habitat in nine 11–22 year old conifer plantations (22–47 ha) where 90–96% of deciduous stems were removed by two treatments: manual thinning, and manual thinning plus application of glyphosate (herbicide). The control and two treatments were replicated three times. We characterized the nest patches of five species: Warbling Vireo (Vireo gilvus), Dusky Flycatcher (Empidonax oberholseri), Swainson's Thrush (Catharus ustulatus), American Robin (Turdus migratorius), and Chipping Sparrow (Spizella passerina). During three post-treatment years, areas treated with thinning plus herbicide remained depauperate of deciduous vegetation whereas thinned sites experienced deciduous regrowth. Despite variation in the density of deciduous trees and in the type of tree used for nesting in the control and treatments, nest patches were positively correlated with the amount of remaining deciduous vegetation, representing habitat that either escaped or recovered from silvicultural treatments. That relationship was stronger in areas with the fewest deciduous trees. Nests were more likely to be successful in areas with more willow. Within a mosaic of managed forest stands, birds appear to use the same proximate habitat cues for selecting a nest patch despite varying fitness consequences across different silviculture regimes. Although birds appeared to compensate for changes in stand habitat by finding patches of untreated vegetation or altering the type of tree they nested in, there was a reproductive cost for some species.
Social and Genetic Monogamy in Territorial and Loosely Colonial Populations of Phainopepla (Phainopepla Nitens)
Authors: Chu Miyoko , Koenig Walter D. , Godinez Alvaro , McIntosh Carl E. , Fleischer Robert C. 
Published: September 2019

Abstract
We observed courtship and copulatory behavior in two populations of Phainopeplas (Phainopepla nitens) with contrasting social systems and used multilocus DNA fingerprinting to assess rates of extrapair fertilization (EPF). Phainopeplas from both territorial and loosely colonial populations copulated infrequently (≤2 times per day). No extrapair copulations (EPCs) were observed in either population. We found no evidence of EPFs in 48 nestlings from 25 nests. Thus, Phainopeplas appear to be both socially and genetically monogamous. However, Phainopeplas are not monogamous over their lifetimes—they do not retain mates from year to year and appear to switch mates between breeding localities within the same year. Compressed breeding seasons, geographically shifting food resources, and widespread breeding failures may favor monogamy during any given breeding attempt while allowing opportunities to switch mates between breeding localities and years.
Soaring Flight in the Eleonora's Falcon (Falco eleonorae)
Authors: Rosén Mikael , Hedenström Anders 
Published: September 2019

AbstractEleonora's Falcon (Falco eleonorae) breeds in the Mediterranean region and is highly adapted for catching small birds on passage migration between Eurasia and their African winter quarters, which they feed their young. We studied gliding flight behavior of Eleonora's Falcon at a breeding colony located on a small island southwest of Sardinia, Italy. Gliding and soaring flight performance was measured using an optical range finder and evaluated against flight mechanical theory. The male falcon does the majority of hunting and usually sets off from the colony to hunting areas located at high altitude over the open sea to catch prey. To lower the cost of transport and maximize the energy gain from hunting, we show that the birds use vertical winds for soaring when available. The occurrence of rising air changes with wind direction. At north-northwesterly winds (on-shore), slope lift is available outside the nesting cliffs, and at south-southeasterly winds thermals that form over the island drift out over the sea. Our observations demonstrated the flexibility of flight behavior in relation to the wind situation, and birds thereby make full use of available soaring conditions.
Did Blue Eggs of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) Cuckoos Evolve to Counter Host Discrimination?
Authors: Lorenzana Janice C. , Sealy Spencer G. 
Published: September 2019

AbstractHughes (1997) hypothesized that the blue coloration of Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoo eggs evolved in response to egg discrimination by their hosts. From that hypothesis, we predicted that cuckoo hosts would eject ancestral nonmimetic (white) eggs, but be more likely to accept mimetic (blue) eggs. American Robins (Turdus migratorius) and Gray Catbirds (Dumetella carolinensis) were used to test that hypothesis because they are ejecter species that lay blue eggs and have been parasitized by Coccyzus cuckoos. Hughes' egg-mimicry hypothesis was not supported because robins and catbirds did not significantly eject white cuckoo eggs more frequently than blue cuckoo eggs. Indeed, most robins accepted both egg types. Furthermore, the observational evidence for egg mimicry is not convincing because only 5 of the 15 host species that Hughes (1997) described as having eggs that “fully or nearly match” the egg color of Black-billed and Yellow-billed cuckoos actually do so.
Molt-Migration in Western Tanagers (Piranga Ludoviciana): Age Effects, Aerodynamics, and Conservation Implications
Authors: Butler Luke K. , Donahue Michael G. , Rohwer Sievert 
Published: September 2019

AbstractWe describe timing and location of the prebasic molt in Western Tanagers (Piranga ludoviciana), focusing on age class differences in premolt movements. Most adults migrate south to the American Southwest where they stop to molt before moving on to their wintering grounds. Molting adults are found in southern mountain regions (Sierra Madres and southern Rockies) and in the Mexican monsoon region, where late summer rains cause a substantial increase in productivity. In contrast, juvenile Western Tanagers move to nearby montane habitats to molt before migrating, a previously undocumented strategy in western passerines that show molt-related movements. By molting in nearby montane habitats, juveniles avoid the aerodynamic cost of migrating in their “fluffy”, aerodynamically inefficient juvenal plumage. Western Tanagers are the fifth species known to use the Mexican monsoon region during the prebasic molt, further affirming the importance of that area to the conservation of Neotropical migrants that breed in western North America.
Massive Collapse and Rapid Rebound: Population Dynamics of Eared Grebes (Podiceps nigricollis) During an ENSO Event
Authors: Jehl Joseph R. , Boyd W. Sean , Paul Don S. , Anderson Daniel W. 
Published: September 2019

Abstract
In autumn, >99% of North American Eared Grebes (Podiceps nigricollis) stage at Mono Lake, California, and Great Salt Lake, Utah, creating an exceptional opportunity to measure population trends in a common and otherwise widely distributed species. Aerial photocounts showed that numbers at both lakes fluctuated in parallel, from a total of ∼3.56 million in 1997, then crashing to 1.60 million in 1998. The decline was coincident with a major El Niño, during which hundreds of thousands starved in the Gulf of California. The population rebounded to 3.27 million by 2000, illustrating the species' potentially high survivorship throughout the year. Catastrophic events are evidently the major factors affecting proximate changes in population size. Factors that set the ultimate limit to the population can be clarified through long-term studies at staging areas.
Territoriality and Neighbor Assessment in Brown Jays (Cyanocorax Morio) in Costa Rica
Authors: Hale Amanda M. , Williams Dean A. , Rabenold Kerry N. 
Published: September 2019

AbstractDefense of group-held resources is a common and widely accepted function of territorial interactions between neighboring groups. In addition, territorial interactions could provide opportunities to assess members of neighboring groups and reproductive opportunities there, or to solidify status in the home group. We studied group-level characteristics and individual participation in territorial encounters in the cooperatively breeding Brown Jay (Cyanocorax morio). Intergroup encounters at stable territory boundaries include both aggressive and affiliative behavior, which suggests that a territorial encounter could function as both a resource defense mechanism and as an arena for social interactions. Territory characteristics that increase the probability of contact between groups (long boundaries, large combined group size, and home range overlap) explain much of the variation in frequency of territorial encounters. Male-biased dispersal was more common to neighboring groups with long boundaries, supporting the idea that frequent interactions between neighbors facilitate dispersal. Females usually inherit breeding positions on their natal territories, and participation in intergroup encounters by females does not vary with age or breeding status. In addition to defending group resources, females on their natal territories could be defending their positions in the breeding queue. Immigrant females are not likely to breed successfully, or to disperse again, and they participated less than expected. Participation by both natal and immigrant males varied by age; young males, at the ages when dispersal and intergroup forays are most likely, participated more than expected, whereas older males (≥4 years) participated less. That is consistent with the hypothesis that participation in intergroup encounters facilitates dispersal and improves integration into social groups. Because extragroup matings occur in this population, both breeding females and males could be assessing neighboring individuals for mating opportunities. Resource defense and social facilitation are not mutually exclusive hypotheses, and our observations suggest that both are important components of territorial encounters in Brown Jays.
Reproduction of Plain Pigeons (Columba Inornata Wetmorei) in East-Central Puerto Rico
Authors: Rivera-Milán Frank F. , Ruiz Carlos A. , Cruz José A. , Sustache José A. 
Published: September 2019

AbstractThe Puerto Rican Plain Pigeon (Columba inornata wetmorei) was listed as endangered in 1970. Transect-survey and nest-monitoring data were collected to estimate reproductive parameters and to assess effects of weather, food, predation, and habitat. We monitored 377 of 423 nests found in east-central Puerto Rico during February-September 1986-2000. The largest sampling effort was conducted in May-June 1998, and 131 nests were found along 8,460 m, resulting in a nest density (D̂) of 5.26 per hectare or 356 nesting pairs (N̂) in the surveyed area (a = 67.7 ha). Nest spatial distribution was highly clumped (b̂ = 3.2) and transect surveys were highly variable (CV = 40%). Thus, 34,000 m needed to be surveyed for a desired coefficient of variation (CV[D̂]) of 20%. Nest density varied widely during May-June 1986–2000. With a CV about the trend line of 121%, from 18 to 28 years of data would be needed to detect an increase or a decrease (r) of 5–10% in log-transformed nest density estimates through linear regression analysis (alpha = 0.15 and power = 0.80). Whereas food abundance had positive and significant relationships with nest density and number of fledglings produced, predator density had negative and significant relationships with nesting success and the number of fledglings produced. Predation accounted for 79% of nest losses (n = 183). Mayfield's estimates of nesting success averaged 40% and an average of 0.5 fledglings were produced per nesting pair. Because Plain Pigeons are able to produce fledglings from three or more broods per year and have extended nesting seasons (with a nest density peak usually occurring in May-June), we hypothesized that hatch-year and after-hatch-year survival rates of 50–65% and a yearly productivity of 1.4–2.0 fledglings per nesting pair were enough to offset mortality. Our optimism is tempered by the fact that Plain Pigeons have not been reported nesting outside east-central Puerto Rico, where rapid destruction and fragmentation of second-growth forests, catastrophic weather, food availability, nest predation, illegal hunting and poaching of nestlings may interact and cause an irreversible population decline. Managers should focus on conserving and restoring second-growth forest fragments to provide food and cover throughout the year. Additional recommendations are given based on the results of our study, which was part of a larger study of factors affecting the reproduction of columbids on Puerto Rico and its territories.
Experimental Test of the Importance of Preen Oil in Rock Doves (Columba Livia)
Authors: Moyer BrettR. , Rock Alex N. , Clayton Dale H. 
Published: September 2019

Abstract
Most species of birds have a uropygial gland, also known as a preen gland, which produces oil that birds spread through their plumage when preening. The plumage of waterfowl deprived of uropygial oil becomes brittle and is subject to breakage. For other groups of birds, however, the importance of preen oil remains unclear. Previous workers have argued that preen oil may serve little or no function in Columbiforms (pigeons and doves). We tested that assertion by removing uropygial glands from Rock Doves (Columba livia) and assessing their plumage condition after several months. The results of that experiment showed significant degradation of plumage in the absence of oil. Our results are the first rigorous demonstration that preen oil is important for plumage condition in nonwaterfowl.
We tested one possible function of preen oil—that it has insecticidal properties and that reduction in plumage condition on birds without glands is due to an increase in ectoparasites. We tested that hypothesis for feather-feeding lice (Phthiraptera:Ischnocera) using both in vitro and in vivo experiments. Lice raised in an incubator died more rapidly on feathers with preen oil than on feathers without oil, which suggests that preen oil may help combat lice. However, removal of the preen gland from captive birds had no significant effect on louse loads over the course of a four-month experiment. Although the results of our in vivo experiments suggest that preen oil may not be an important defense against lice, further experiments are needed. We also consider the possibility that preen oil may protect birds against other plumage-degrading organisms, such as bacteria and fungi.
The Birds of Ecuador, Volume I: Status, Distribution, and Taxonomy. Volume II: Field Guide
Authors: Rowlett John 
Published: September 2019

AbstractThe 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.