bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic and Demographic Criteria for Defining Population Units for Conservation: The Value of Clear Messages
Authors: Esler Daniel , Iverson Samuel A. , Rizzolo Daniel J. 
Published: September 2019

Abstract
In a recent paper on Harlequin Duck (Histrionicus histrionicus) interannual site fidelity (Iverson et al. 2004), we concluded that wintering populations were demographically structured at a finer geographic scale than that at which genetic differentiation was observed and that conservation efforts should recognize this degree of demographic independence. In a critique of our study, Pearce and Talbot (2006) contend that our measures of fidelity were not robust and imply that in the face of “mixed messages” we failed to appreciate the role of genetic data in defining population units. We recognize, as we did in our original paper, that our methods for quantifying site fidelity have some limitations; however, the patterns in our data are consistent with a considerable body of literature indicating high winter site fidelity in Harlequin Ducks. Moreover, we do not consider differences in the scales at which genetic and demographic structure are expressed to be “mixed messages,” given the different spatial and temporal scales at which genetic and contemporary demographic processes operate. We emphasize that a lack of genetic differentiation does not necessarily preclude the existence of contemporary demographic structure with relevance for conservation.
Intraspecific Phylogeography and Adaptive Divergence in the White-Headed Woodpecker
Authors: Alexander Matthew P. , Burns Kevin J. 
Published: September 2019

AbstractThis study uses mitochondrial DNA (mtDNA) to examine the phylogeography of the White-headed Woodpecker (Picoides albolarvatus), one of the least-studied woodpeckers in North America. A mismatch distribution and calculation of Tajima's D indicate that the overall phylogeographic history of the species is characterized by a recent range expansion that probably occurred after the start of the Pleistocene. In addition, a nested clade phylogeographic analysis indicates that additional processes such as allopatric fragmentation and restricted gene flow have influenced the evolutionary history of this species. Traditionally, the White-headed Woodpecker has been split into two subspecies whose distributions meet in the northern part of the Transverse Ranges in California. The two subspecies differ morphologically, with the southern subspecies having a larger bill in proportion to its body size than the northern subspecies. Geographical variation in mtDNA is concordant with a division at the Transverse Ranges that corresponds to the morphological variation seen between the two subspecies. An analysis of molecular variance indicates that 27% of the genetic variation results from differences between the northern and southern subspecies. Furthermore, birds in the northern part of the range differ from those in the southern part of the range by at least one base substitution. These results agree with the hypothesis that the larger bill of the southern subspecies is the result of recent local adaptation to feeding on the large cones of Coulter pines (Pinus coulteri).
Song Learning by Chipping Sparrows: When, Where, and From Whom
Authors: Liu Wan-Chun , Kroodsma Donald E. 
Published: September 2019

AbstractGiven the difficulty of following free-living, dispersing juvenile songbirds, relatively little is known about when, where, how, and from whom these young birds learn their songs. To explore these issues, we studied the Chipping Sparrow (Spizella passerina), males of which have a single, simple song, but populations of which may contain 20–30 different songs. In our western Massachusetts study sites, we color-banded 324 nestling and 32 fledgling sparrows. Twelve of these banded males returned to our study areas, dispersing a few hundred meters to 1.8 km away from their natal territories. The song of each yearling closely matched only one of his immediate neighbors on the breeding territory, revealing that a yearling sparrow precisely imitates one of his close neighbors after dispersal. Evidence from this field study and a previous laboratory study show that a young male is able to learn songs either during his hatching year or the following spring, perhaps depending on his chances of song exposure or social interaction with territorial neighbors.
Territoriality, Site Fidelity, and Survivorship of Willow Flycatchers Wintering in Costa Rica
Authors: Koronkiewicz Thomas J. , Sogge Mark K. , Van Riper Charles , Paxton Eben H. 
Published: September 2019

AbstractWe studied wintering Willow Flycatchers (Empidonax traillii) in two seasonal freshwater wetland habitats in northwestern Costa Rica during five boreal winters, to determine habitat occupancy, overwinter and between-year site and territory fidelity, and the degree to which the sexes maintain and defend winter territories. Both males and females used agonistic displays, song, and other vocalizations to maintain and defend mutually exclusive winter territories. Males were generally more abundant than females, but this varied by site and year. There was no significant difference in male and female territory size, nor any indication of sexual habitat segregation. Similarity in morphology and aggressiveness between the sexes may account for the lack of habitat segregation and the ability of females to maintain territories at wintering sites. Each year, 80%–92% of banded flycatchers that were present in midwinter remained at the site until late winter; of these, 86%–100% of individuals maintained the same territories throughout the entire period. We also observed nonterritorial floaters that subsequently established and held winter territories. Between-year site fidelity averaged 68%, and almost all returning birds established territories with boundaries similar to the previous year. Between-year apparent survivorship estimates ranged annually from 54%–72%, with no difference between sites but weak support for higher survivorship of males compared to females. Values for winter site and territory fidelity were generally higher than those reported for other species and for Willow Flycatchers on the breeding grounds; between-year survivorship estimates were similar to those reported for breeding flycatchers.
Geographic Variation in the Trade-Off Between Nestling Growth Rate and Body Condition in the Tree Swallow
Authors: Ardia Daniel R. 
Published: September 2019

AbstractNestlings can exhibit considerable variation in developmental patterns both within and among locations due to differences in environmental conditions and parental investment. I investigated trade-offs between nestling growth rate and residual body mass (body condition) at three locations across the range of the Tree Swallow (Tachycineta bicolor). Nestlings at the northern extreme of the range in Alaska had slower growth rates, lower body mass, and higher residual body mass than nestlings in New York and Tennessee. High insect availability was correlated with increased growth rates of nestlings in New York and Tennessee, but not in Alaska. Conversely, nestlings in Alaska showed increased residual body mass with high insect availability, but nestlings in New York and Tennessee did not. The trade-off between growth rate and residual body mass varied among sites, with fast-growing nestlings in Tennessee maintaining a higher residual body mass than those in Alaska. These results suggest that factors affecting offspring growth and condition vary among sites, leading to geographical differences in offspring development trajectories.
Green-Tailed Towhee Response to Prescribed Fire in Montane Shrubland
Authors: Jehle Gretchen , Savidge Julie A. , Kotliar Natasha B. 
Published: September 2019

Abstract
Fire alters the structure and composition of shrublands and affects habitat quality for the associated avifauna. Because shrubland ecosystems have been greatly reduced from their original extent in western North America and fire is increasingly being used to manage these landscapes, a better understanding of how fire affects the associated vegetation and wildlife is imperative. We evaluated the response of Green-tailed Towhees (Pipilo chlorurus) to prescribed fire in the montane shrublands of Rocky Mountain National Park, Colorado during 2002 and 2003. Three to five years following prescribed burning, Green-tailed Towhee density and shrub cover were generally higher in unburned areas. Nests (n  =  179) were located in unburned vegetation; within burned sites, all nests were in remnant patches. Green-tailed Towhee nest survival was 57% (95% CI  =  49%–65%) across the two years of the study. More than half of the nests were in common juniper (Juniperus communis) shrubs, and nest survival was higher for nests in junipers than those in other shrub species. Daily nest survival rates were lower at the site with the highest density of towhees and declined over the breeding season. With regard to shrub cover, opposite trends were observed for nest-site selection and nest survival: nest plots had greater shrub cover than non-nest plots, but nest survival decreased with increasing shrub cover. Because shrub cover affects towhee density and nest survival in conflicting ways, fire management at Rocky Mountain National Park alters both habitat availability and suitability for Green-tailed Towhees.
Relationship Between Aspen Heartwood Rot and the Location of Cavity Excavation by a Primary Cavity-Nester, the Red-Naped Sapsucker
Authors: Losin Neil , Floyd Chris H. , Schweitzer Todd E. , Keller Sarah J. 
Published: September 2019

AbstractWe investigated nest-hole excavation by the Red-naped Sapsucker (Syphrapicus nuchalis) in aspen (Populus tremuloides) woodlands in western Colorado. Sapsuckers excavate nest cavities primarily in aspens infected with a heartwood rot fungus (Phellinus tremulae), which softens the heartwood of infected trees. We assessed the interior condition of fungus-infected aspen trunks by extracting wood samples with an increment corer to determine whether sapsuckers chose nest-hole locations based on the extent of healthy sapwood remaining. Comparing fungus-infected trees with and without cavities, cavity-bearing trees had thinner healthy sapwood. The depth of healthy sapwood also varied with compass direction, being thinnest on the south sides of fungus-infected aspens. Cavity entrance orientations were significantly biased to the south-southeast, corresponding with the directional bias in heartwood rot. These results suggest that the depth of healthy sapwood, and hence excavation effort, may be important in determining nest hole location for the Red-naped Sapsucker.
Sex-Related Natal Dispersal of Pied Flycatchers: How Far Away From Home?
Authors: Chernetsov Nikita , Sokolov Leonid V. , Kosarev Vladislav , Leoke Dmitry , Markovets Mikhail , Tsvey Arseny , Shapoval Anatoly P. 
Published: September 2019

AbstractOver four years, nestling Pied Flycatchers (Ficedula hypoleuca) were banded and recaptured in nest boxes at a 44 km long and 1–1.5 km wide study area along the Courish Spit on the southeast Baltic coast. The return rate for males was nearly twice as high as for females. Males settled significantly closer to their natal sites than predicted by the null model, which assumed that any nest box in the study area was selected at random. For females, the frequency distribution of natal dispersal distances was not significantly different from that predicted by the null model. The difference in average dispersal distance between the sexes was highly significant. Although some individuals settled within tens of kilometers, most male Pied Flycatchers settled within several kilometers of their natal sites. We suggest that even if females settle on average farther from their natal sites than males do, both sexes imprint on a relatively small (several kilometers in diameter) area during postfledging exploration, to which they return each spring.
A Small Suboscine-Like Passeriform Bird from the Early Oligocene of France
Authors: Mayr Gerald , Manegold Albrecht 
Published: September 2019

Abstract
We report the wing bones of a small passeriform bird from the early Oligocene of France, which are among the earliest fossil remains of Passeriformes in Europe. The specimen is clearly distinguished from oscines, to which all extant European passeriforms belong, and closely resembles suboscine passerines in presumably derived features. If future, more complete specimens support its assignment to the suboscines, it would be the earliest fossil record of this passeriform taxon. Together with other fossils from the early Oligocene of Germany, it indicates that nonoscine passerines colonized Europe before the arrival of oscines.
Two New Late Pleistocene Avifaunas From New Mexico
Authors: Brasso Rebecka L. , Emslie Steven D. 
Published: September 2019

Abstract
We report two new late Pleistocene avifaunas from New Mexico, recovered from Sandia Cave during archaeological excavations by F. Hibben in the 1930s and the nearby Marmot Cave excavated in 2000. The fossil assemblage from Sandia Cave consists of at least 30 taxa, including seven extralimital and two extinct species, Coragyps occidentalis (extinct vulture) and Ectopistes migratorius (Passenger Pigeon). The avifauna from Marmot Cave is limited to eight taxa shared with Sandia Cave. Two new records of Gymnogyps californianus (California Condor) are reported from these sites, as well as new records of Lagopus sp. (ptarmigan), Aegolius funereus (Boreal Owl), and Micrathene whitneyi (Elf Owl) from New Mexico. Two new radiocarbon dates on fossil G. californianus from Sandia and Marmot cave are reported at 10 795 ± 50 and 25 090 ± 220 14C years before present (B.P.), respectively. These collections provide further evidence for mixed avian communities in New Mexico during the late Pleistocene and are similar to other cave avifaunas of comparable age from the Great Basin and Rocky Mountain regions. The birds from Sandia Cave that are shared with other fossil avifaunas include species currently found in arctic tundra, boreal, and steppe habitats, as well as open, xeric communities. This collection provides additional evidence for widespread steppe-tundra, shrub, and subalpine forest environments at lower elevations of western North America during the late Pleistocene.
Lifetime Reproductive Success of Bald Eagles in Northern California
Authors: Jenkins J. Mark , Jackman Ronald E. 
Published: September 2019

Abstract
We studied the breeding success of resident Bald Eagles (Haliaeetus leucocephalus) over a 20-year period along the Pit River drainage in northern California. In 258 nesting attempts at 10 intensively studied nesting territories, 0.31 to 1.65 young were produced per year per occupied territory (mean  =  0.97), with average nesting success of 62%. Nineteen individually banded breeding adult Bald Eagles produced from zero to 36 young during their lifetimes, and birds remained on their territories for 1–16 years following capture as adults. We calculated a 90% annual survival rate for breeding adults from our sample of 19 birds, with longevity of one banded eagle at 22 years. Eagles that bred on a territory for a greater number of years did not produce a greater number of young annually on average than other breeding birds. Larger males, as evidenced by body mass at capture, produced significantly more young over their lifetimes than smaller males. This same relationship did not hold for females, however. Seven banded pairs of adults remained together on their territories for 3–15 years. Reproduction decreased significantly following replacement of a breeding adult on a territory, and this effect continued for 2–3 years following replacement.
Eastern Bluebirds Eject Brown-Headed Cowbird Eggs
Authors: Peer Brian D. , Hawkins Lyndon R. , Steinke Edwin P. , Bollinger Patricia Blair , Bollinger Eric K. 
Published: September 2019

AbstractThe relationship between the Brown-headed Cowbird (Molothrus ater) and its cavity-nesting hosts has received little attention because of the assumption that cowbirds rarely parasitize these hosts. We tested the Eastern Bluebird (Sialia sialis), a host that is sometimes heavily parasitized by cowbirds, for egg ejection behavior. Bluebirds ejected 65% of experimentally added cowbird eggs (n  =  20), but ejected no experimentally added conspecific eggs (n  =  66). This suggests that cowbird parasitism, not conspecific brood parasitism, is the selective pressure responsible for egg ejection in this species. This level of rejection may be conservative because bluebirds nest in dark cavities, which may make cowbird eggs difficult to detect by bluebirds.
Sage-Grouse and Indirect Interactions: Potential Implications of Coyote Control on Sage-Grouse Populations
Authors: Mezquida Eduardo T. , Slater Steven J. , Benkman Craig W. 
Published: September 2019

AbstractAbstractCoyotes (Canis latrans) are lethally controlled throughout the range of Greater Sage-Grouse (Centrocercus urophasianus) and it has been suggested that such control may benefit sage-grouse. However, the perceived benefits of control are based on the direct effects of coyotes on sage-grouse and largely ignore potential indirect interactions. Here, we summarize some of the evidence for direct effects in a simplified food web including coyotes and sage-grouse. There is very little evidence to suggest that coyotes have much of a direct negative effect on sage-grouse, but there is considerable evidence supporting direct interactions that would lead to positive indirect effects between coyotes and sage-grouse. The three likely forms of positive indirect effects arise because coyotes reduce the potential negative effects resulting from mesopredator release and apparent and exploitative competition. Mesopredator release would adversely affect sage-grouse if a decrease in coyotes allowed an increase in foxes (especially Vulpes vulpes), badgers (Taxidea taxus), and Common Ravens (Corvus corax), mesopredators that prey on sage-grouse eggs and young. A decrease in coyotes is likely to allow jackrabbits (Lepus spp.) to increase, which would cause sage-grouse to suffer from apparent competition if Golden Eagles (Aquila chrysaetos), which are perhaps the most important predator of adult sage-grouse, then increase in response to the increase in jackrabbits. This increase in jackrabbits may also depress the availability of sagebrush (Artemisia spp.) and forbs, leading to an increase in exploitative competition with sage-grouse. For these reasons, we argue that intense and extended lethal coyote control is likely detrimental to sage-grouse conservation.
Does The Presence of Barred Owls Suppress the Calling Behavior of Spotted Owls?
Authors: Crozier Michelle L. , Seamans Mark E. , GutiÉRrez R. J. , Loschl Peter J. , Horn Robert B. , Sovern Stan G. , Forsman Eric D. 
Published: September 2019

Abstract

Abstract
Barred Owls (Strix varia) have expanded their range throughout the ranges of Northern (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis). Field observations have suggested that Barred Owls may be behaviorally dominant to Spotted Owls. Therefore, we conducted a test of behavioral dominance by assessing responsiveness of Spotted Owls to conspecific calls when they were in the simulated presence (i.e., imitation of Barred Owl vocalizations) of a Barred Owl. We hypothesized that Spotted Owls would be less likely to respond to conspecific calls in areas where Barred Owls were common. We used a binary 2 × 2 crossover experimental design to examine male Spotted Owl responses at 10 territories randomly selected within two study areas that differed in abundance of Barred Owls. We also conducted a quasi experiment at four study areas using response data from any Spotted Owl (male or female) detected following exposure to Barred Owl calls. We inferred from the crossover experiment that the simulated presence of a Barred Owl might negatively affect Spotted Owl responsiveness. Both subspecies of Spotted Owl responded less to Spotted Owl calls after exposure to Barred Owl calls, Northern Spotted Owls responded less frequently in areas having higher numbers of Barred Owls, and California Spotted Owls responded less frequently than Northern Spotted Owls overall.
Climate Change Effects on Neotropical Manakin Diversity Based on Ecological Niche Modeling
Authors: Anciães Marina , Peterson A. Townsend 
Published: September 2019

AbstractAbstractAssessing the nature and magnitude of potentialeffects of climate change on populations isimportant to anticipating effects on speciesdiversity for conservation planning. We usedecological niche modeling to predict present andfuture distributions of 49 species of manakins(Pipridae) and allies. Predictions forpresent-day distributions were highly coincidentwith independent test data, suggesting goodpredictive ability. Assuming no dispersal,projections of potential distributions underfour scenarios of climate change predicted that20% of manakin species would likely goextinct from their current ranges, and thatdistributions would in general be reduced andfragmented, regardless of the area ofpresent-day potential distribution or rarity.Predicted changes in potential distributions,spatial configuration of suitable habitats, andgeographic position of species ranges were moredramatic for species inhabiting flatlands thanfor montane species. These results are anexample of how ecological niche modelingtechniques can anticipate the nature andmagnitude of changes in biodiversity in responseto climate change.
The Role of Food, Nest Predation, and Climate in Timing of Wrentit Reproductive Activities
Authors: Preston Kristine L. , Rotenberry John T. 
Published: September 2019

Abstract

Abstract
Timing of breeding activities by birds hasimportant fitness consequences, as deciding when tonest can affect nest success. For three breedingseasons, we provided supplemental food to Wrentits(Chamaeafasciata) inhabitingsemiarid shrublands. We tested the effects of foodsupplementation on timing of initial egg laying,number of nests attempted, timing of fledging, andlength of the breeding season. We also evaluatedwhether Wrentits timed nest initiation to avoidperiods of greatest predation risk. Our study wasconducted during a period of high interannualvariation in precipitation. Supplemental food didnot advance laying date in Wrentits. During adrought, even Wrentits given supplemental fooddelayed nesting, initiated fewer nesting attempts,fledged young earlier, and reduced the length ofthe breeding season. In a year of average rainfall,supplemental food allowed pairs to continuerenesting late into the summer, after repeated nestlosses from predation. Wrentits did not timenesting to avoid periods of greatest predationrisk. In timing initial breeding, Wrentits appearedto be responding to climatic conditions and toindirect cues that predicted environmentalconditions later in the breeding season rather thanto food availability at the time of egg laying.