bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex, Wingtip Shape, and Wing-Loading Predict Arrival Date at a Stopover Site in the Swainson's Thrush (Catharus Ustulatus)
Authors: Bowlin Melissa S.
Published: September 2019

Pointed wingtips and low wing-loading are believed to reduce the amount of energy used during migratory flight. If this is true, individuals with pointed wingtips or consistently low wing-loading should be able to migrate faster than conspecifics and may arrive on the breeding grounds and at stopover sites earlier. To test this hypothesis, I captured 97 Swainson's Thrushes (Catharus ustulatus; hereafter “thrushes”) during May in three consecutive field seasons, 2003-2005, at a stopover site in central Illinois. I used molecular techniques to sex 47 of these thrushes and created a discriminant function analysis using wing, tarsometatarsus, and tail lengths that predicted sex with 80.9% accuracy (P < 0.001). I applied this function to the remaining 50 thrushes so that I could control for any sexual dimorphism in morphology and arrival timing, and then examined seasonal trends in sex and morphology. Male thrushes arrived earlier at my stopover site than females (P < 0.001). After controlling for sex, thrushes with more pointed wingtips (P = 0.002) and lower wing-loading (P = 0.044) arrived earlier than thrushes with more rounded wingtips and higher wing-loading. The general linear model with sex, wingtip pointedness, and wing-loading explained nearly one-third of the variation in arrival date (P < 0.001, r2 = 0.281, n = 90). Pointed wingtips and lower wing-loading may help migratory birds cover distance more quickly and arrive at the breeding grounds sooner; alternatively, thrushes with more pointed wingtips and lower wing-loading may have departed from the wintering grounds earlier. If wing shape and size affect rate of migration, these variables may be important determinants of individual quality in migratory passerines.

El Sexo, la Forma de las Puntas de las Alas y la Carga Alar Predicen la Fecha de Arribo de Catharus ustulatus a un Sitio de Escala Migratoria
Pelicans, Cormorants, and Their Relatives: The Pelecaniformes
Authors: Schreiber E. A.
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.
Three-dimensional chromosome organization in flowering plants
Authors: Grob Stefan
Published: September 2019

Research on plant three-dimensional (3D) genome architecture made rapid progress over the past 5 years. Numerous Hi-C interaction data sets were generated in a wide range of plant species, allowing for a comprehensive overview on 3D chromosome folding principles in the plant kingdom. Plants lack important genes reported to be vital for chromosome folding in animals. However, similar 3D structures such as topologically associating domains and chromatin loops were identified. Recent studies in Arabidopsis thaliana revealed how chromosomal regions are positioned within the nucleus by determining their association with both, the nuclear periphery and the nucleolus. Additionally, many plant species exhibit high-frequency interactions among KNOT entangled elements, which are associated with safeguarding the genome from invasive DNA elements.

Many of the recently published Hi-C data sets were generated to aid de novo genome assembly and remain to date little explored. These data sets represent a valuable resource for future comparative studies, which may lead to a more profound understanding of the evolution of 3D chromosome organization in plants.
Spectrum: fast density-aware spectral clustering for single and multi-omic data
Authors: John Christopher R , Watson David , Barnes Michael R , Pitzalis Costantino , Lewis Myles J
Published: September 2019

Motivation

Clustering patient omic data is integral to developing precision medicine because it allows the identification of disease subtypes. A current major challenge is the integration multi-omic data to identify a shared structure and reduce noise. Cluster analysis is also increasingly applied on single-omic data, for example, in single cell RNA-seq analysis for clustering the transcriptomes of individual cells. This technology has clinical implications. Our motivation was therefore to develop a flexible and effective spectral clustering tool for both single and multi-omic data.

Results

We present Spectrum, a new spectral clustering method for complex omic data. Spectrum uses a self-tuning density-aware kernel we developed that enhances the similarity between points that share common nearest neighbours. It uses a tensor product graph data integration and diffusion procedure to reduce noise and reveal underlying structures. Spectrum contains a new method for finding the optimal number of clusters (K) involving eigenvector distribution analysis. Spectrum can automatically find K for both Gaussian and non-Gaussian structures. We demonstrate across 21 real expression datasets that Spectrum gives improved runtimes and better clustering results relative to other methods.

Availability and implementation

Spectrum is available as an R software package from CRAN https://cran.r-project.org/web/packages/Spectrum/index.html.

Supplementary information

Supplementary data are available at Bioinformatics online.
Quality by design applied to olanzapine and quetiapine LC-MS/MS bioanalysis
Authors: da Mota Castelo Branco Daniel , Bedor Noely Camila Tavares Cavalcanti , Silva Carolina Santos , Bedor Danilo César Galindo , Pimentel Maria Fernanda , de Santana Davi Pereira
Published: September 2019

One major challenge in quantifying drugs in biological matrices is to manage interfering compounds. A technique such liquid chromatography coupled to mass spectrometry in tandem (LC-MS/MS) is especially suitable for this application due to its high sensitivity and selectivity in detecting low concentrations of analytes in a complex system. Due to the complexity of LC-MS/MS systems, a number of experimental parameters must be optimized to provide an adequate separation and detection of the analyte. In the present work, a design of experiments approach was developed to optimize an LC-MS/MS-based bioanalytical method to extract olanzapine (OLZ) and quetiapine (QTP) from human plasma. Three steps for the optimization process were conducted: central composite face-centered design to optimize chromatographic parameters (Step 1), ionization in mass spectrometry (Step 2) and a full 32 factorial design to optimize analyte extraction conditions (Step 3). After the optimization process, resolutions and QTP and OLZ retention time (2.3 and 4, respectively) were optimum with pH of 4.7 and 85.5% of acetonitrile for the chromatographic step. Mass spectrometry optimization step provided an increase of (±50%) in the average peak area with high signal-to-noise relationship for the analytes studied. The proposed extraction method was 70% more efficient than the initial method for all drugs analyzed.
Partial Migration, and Lek and Nesting Area Fidelity in Female Great Bustards
Authors: Alonso Juan C. , Morales Manuel B. , Alonso Javier A.
Published: September 2019

We examined the seasonal movements of wing-tagged and radio-marked adult female Great Bustards Otis tarda in a population in northwestern Spain. Four different movement patterns were found: females that migrated between breeding and wintering areas (20%), females that only left their year-round home range area to mate (32%), females that migrated from a wintering-mating area to a nesting-summering area (16%), and females that stayed all year round within a relatively small home range area (32%). All females displayed fidelity to their nesting and wintering areas, and most also showed fidelity to their leks. Migration patterns were not affected either in timing or distance by breeding success. The maximum distance between natal and dispersal locations during their first year of life was significantly higher in migratory females than in sedentary ones. These patterns explained the seasonal variations in population numbers observed in the study area. Surveys showed that the number of females increased from 600–700 breeding birds, with 1,000–1,100 birds present from October to March.
Molecular Genetic Status of Aleutian Canada Geese From Buldir and the Semidi Islands, Alaska
Authors: Pierson Barbara J. , Pearce John M. , Talbot Sandra L. , Shields Gerald F. , Scribner Kim T.
Published: September 2019

We conducted genetic analyses of Aleutian Canada Geese (Branta canadensis leucopareia) from Buldir Island in the western Aleutians and the Semidi Islands in the eastern portion of their breeding range. We compared data from seven microsatellite DNA loci and 143 base pairs of the control region of mitochondrial DNA from the two populations of Aleutian Canada Geese and another small-bodied subspecies, the Cackling Canada Goose (B. c. minima) which nests in western Alaska. The widely separated island-nesting Aleutian geese were genetically more closely related to each other than to mainland-nesting small-bodied geese. The populations of Aleutian geese were genetically differentiated from one another in terms of mitochondrial DNA haplotype and microsatellite allele frequencies, suggesting limited contemporary gene flow and/or major shifts in gene frequency through genetic drift. The degree of population genetic differentiation suggests that Aleutian Canada Goose populations could be considered separate management units. There was some evidence of population bottlenecks, although we found no significant genetic evidence of non-random mating or inbreeding.
Short Communications the Breeding System of the Orange-Crowned Manakin
Authors: Alonso José Alvarez
Published: September 2019

I studied the lek organization and courtship displays of the Orange-crowned Manakin (Heterocercus aurantiivertex) in undisturbed, lowland rain forest in northeastern Peru. The majority of leks were in seasonally flooded or swampy forest, and most were situated around the borders of old ox-bow lakes. Males maintain loosely packed courts inside exploded leks or “quasi leks,” which may extend for more than 1 km. Within leks, males vocalize throughout the day and occasionally perform two distinctly different solitary displays. One is a spectacular aerial performance that begins above the canopy. The “log display” is performed just above ground- or water-level and consists of a series of short, ritualized jumps.
Long-Term Pair Bonds in Harlequin Ducks
Authors: Smith Cyndi M. , Cooke Fred , Robertson Gregory J. , Goudie R. Ian , Boyd W. Sean
Published: September 2019

We documented the frequency of pair reunion in Harlequin Ducks (Histrionicus histrionicus) on breeding streams in Alberta, and at a molting/wintering area in southwestern British Columbia. As long as their mate is alive, Harlequin Duck pairs reunite on the wintering area and return to the breeding stream together. Pairs reunite even if the female is unsuccessful at breeding the previous season, which suggests that reuniting with the same mate year after year is important. Some males that have lost their mate and fail to re-pair on the wintering area show fidelity to their former breeding site.
Population Declines of King and Common Eiders of the Beaufort Sea
Authors: Suydam Robert S. , Dickson D. Lynne , Fadely Janey B. , Quakenbush Lori T.
Published: September 2019

King (Somateria spectabilis) and Common Eiders (S. mollissima v-nigra) wintering off western North America migrate past Point Barrow, Alaska and across the Beaufort Sea to nest in northern Alaska and northwestern Canada. Migration counts were conducted by various researchers at Point Barrow during 1953, 1970, 1976, 1987, 1994, and 1996. We examined population trends by standardizing the analysis of the migration counts in all years. Based on this standardized procedure, the King Eider population appeared to remain stable between 1953 and 1976 but declined by 56% (or 3.9% year−1) from approximately 802,556 birds in 1976 to about 350,835 in 1996. The Common Eider population declined by 53% (or 3.6% year−1) from approximately 156,081 birds in 1976 to about 72,606 in 1996. Reasons for the declines are unknown.
Faunal Remains in California Condor Nest Caves
Authors: Collins Paul W. , Snyder Noel F. R. , Emslie Steven D.
Published: September 2019

Studies of faunal remains in California Condor (Gymnogyps californianus) nests in the 1980s yielded bones and hair of a variety of small, medium-sized, and large mammals, and a near absence of avian and reptilian materials. A prevalence of small to medium-sized species may reflect ease of penetration of hides of such carrion and a relative abundance of ingestible bone from such species. Remains also included metal, plastic, and glass artifacts, likely mistaken for bone materials by condors. Size distributions of bone materials and percentage artifacts among hard remains suggest an overall absence of severe calcium-supply problems for condors.
Body Weight and Feather Growth of Male Barrow's Goldeneye During Wing Molt
Authors: van de Wetering Debbie , Cooke Fred
Published: September 2019

We studied the timing, duration, and rate of wing molt of male Barrow's Goldeneye (Bucephala islandica). The mean daily change in primary feather length was 2.6%, which is consistent with rates reported for other waterfowl species. The mean length of the flightless period was 31 days (range: 27–34 days), excluding the pre-shedding interval. Wing molt extended from early July to mid-September. Peak wing molt occurred between 20 July and 23 August. The mean body weight of adult males decreased significantly during wing molt. Heavier birds had greater remigial growth rates and experienced more substantial declines in body weight than lighter birds, suggesting that body reserves may be used to increase the rate of remigial growth.
A Tale of two Strategies: Life-History Aspects of Family Strife
Authors: Forbes Scott , Mock Douglas W.
Published: September 2019

Breeding birds can generally be thought of as having evolved life-history traits that tend to maximize lifetime reproductive success. Within this broad pattern, many variations are possible because all traits are co-evolved with numerous others in complex ways. Clutch-size, for example, has long been understood to be frequently lower than the number of young parents are capable of supporting by working at their top capacity, especially in long-lived species. Nevertheless, studies of species with fatal competition among nestmates have shown that parents routinely create one offspring more than they normally will raise, as if counting on brood-reduction to trim family size after hatching. Three general and mutually compatible parental incentives for initial over-production have been identified, with David Lack's resource-tracking hypothesis having received the most attention. Extra sibs can also assist each other in some circumstances, but a third explanation for over-production that has been around for nearly four decades, the insurance hypothesis, has been surprisingly overlooked and, in some cases, actively challenged. It simply posits that parents create extra offspring as back-ups for members of the core brood that chance to die very early. We propose that the skepticism over the role of insurance is misdirected, that having a back-up is virtually automatic as a contributing incentive to parents and, in some taxa, that it provides a necessary and totally sufficient explanation for over-production. Some empirical approaches to the study of the insurance hypothesis are reviewed, in hopes of encouraging further field study of over-production in general, because that process underlies much of the internal conflict observed in avian families.
Copulation Behavior, Mate Guarding, and Paternity in the Semipalmated Plover
Authors: Zharikov Yuri , Nol Erica
Published: September 2019

We present behavioral observations and multilocus DNA fingerprinting data on Semipalmated Plovers (Charadrius semipalmatus) breeding in the sub-Arctic. We predicted that, where a large time/energy investment by males during incubation and chick-rearing is crucial for successful reproduction, both extra-pair copulation and fertilization rates would be low. Extra-pair copulations were infrequent (7% of total copulations), as were within pair copulations (0.44 hr−1). Copulations occurred, on average 6.2 days prior to clutch initiation. Males spent 64% of their time in visual contact with their mates. Mate guarding during the laying period was significantly more pronounced in coastal neighborhoods of breeding birds than among solitary-nesting pairs. Extra-pair fertilizations occurred in 4% of families resulting in an extra-pair paternity rate of 4.7%.
Lack, Skutch, and Moreau: The Early Development of Life-History Thinking
Authors: Ricklefs Robert E.
Published: September 2019

Papers by Reginald Moreau, David Lack, and Alexander Skutch published during the 1940s set the stage for the development of thinking about life histories over the following decades. Lack was concerned about the fundamental issue of individual vs. group selection and turned life-history evolution into a battleground for this debate. His monolithic focus on nesting success as a measure of fitness and on food availability as the principal determinant of nesting success obscured the rich empirical background brought to the debate by Skutch and the diverse evolutionary forces envisioned by Moreau. Lack's strong convictions, single-mindedness, and eloquence forced biologists to confront several important problems but also held back the full development of life-history theory until the mid-1960s. Retrospective consideration of these early life-history studies shows how science can progress through a balance of conviction and reflection.
The Phylogenetic Approach to Avian Life Histories: An Important Complement to Within-Population Studies
Authors: Winkler David W.
Published: September 2019

In recent years, two approaches have emerged for the analysis of character evolution: the largely statistical “convergence” approach and the mainly cladistic “homology” approach. I discuss the strengths and weaknesses of these approaches as they apply to phylogenetic analyses of life-history variation in birds. Using examples from analyses of character variation in swallows, I suggest that the phylogenetic approach yields distinctive insights into the selective role of the environment and other characters of the organism on the evolution of life-history traits. This view thus has the potential of bringing together micro- and macro-evolutionary views of life-history evolution.
Sound Design for Vocalizations: Quality in the Woods, Consistency in the Fields
Authors: Brown Timothy J. , Handford Paul
Published: September 2019

The acoustic adaptation hypothesis (AAH) predicts that vocalizations intended for unambiguous long range communication should possess amplitude modulation (AM) characteristics such that the temporal patterning of amplitude degrades less than alternative patterns during transmission through native habitat. The specific predictions are that open habitat signals should be structured as rapid AM trills, whereas closed habitat signals should be structured as low-rate AM tonal whistles. To investigate the benefit of trill- and whistle-structured signals in open and closed habitats, respectively, a high and low carrier frequency set of four synthetic signals which ranged from rapid AM trills to low rate AM whistles were transmitted 3 hours after sunrise through five different habitat types ranging from closed mature forest to open grassland. Results indicate that, on average, whistles degrade less than trills in both habitats. Trills benefit in open habitats through their tendency to be received with a more consistent quality than whistles. Such differences in transmission consistency among AM patterns are not found in closed habitats. While not degrading less on average, lower frequency signals are received with a more consistent quality than are higher frequency signals of the same AM structure, in both open and closed habitats.
Density Dependence, Evolutionary Optimization, and the Diversification of Avian Life Histories
Authors: Ricklefs Robert E.
Published: September 2019

Although we have learned much about avian life histories during the 50 years since the seminal publications of David Lack, Alexander Skutch, and Reginald Moreau, we still do not have adequate explanations for some of the basic patterns of variation in life-history traits among birds. In part, this reflects two consequences of the predominance of evolutionary ecology thinking during the past three decades. First, by blurring the distinction between life-history traits and life-table variables, we have tended to divorce life histories from their environmental context, which forms the link between the life history and the life table. Second, by emphasizing constrained evolutionary responses to selective factors, we have set aside alternative explanations for observed correlations among life-history traits and life-table variables. Density-dependent feedback and independent evolutionary response to correlated aspects of the environment also may link traits through different mechanisms. Additionally, in some cases we have failed to evaluate quantitatively ideas that are compelling qualitatively, ignored or explained away relevant empirical data, and neglected logical implications of certain compelling ideas. Comparative analysis of avian life histories shows that species are distributed along a dominant slow-fast axis. Furthermore, among birds, annual reproductive rate and adult mortality are directly proportional to each other, requiring that pre-reproductive survival is approximately constant. This further implies that age at maturity increases dramatically with increasing adult survival rate. The significance of these correlations is obscure, particularly because survival and reproductive rates at each age include the effects of many life-history traits. For example, reproductive rate is determined by clutch size, nesting success, season length, and nest-cycle length, each of which represents the outcome of many different interactions of an individual's life-history traits with its environment. Resolution of the most basic issues raised by patterns of life histories clearly will require innovative empirical, modeling, and experimental approaches. However, the most fundamental change required at this time is a broadening of the evolutionary ecology paradigm to include a variety of alternative mechanisms for generating patterns of life-history variation.
Evidence for Edge Effects on Multiple Levels in Tallgrass Prairie
Authors: Winter Maiken , Johnson Douglas H. , Faaborg John
Published: September 2019

We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeared to be caused mainly by greater exposure of nests to mid-sized carnivores. We argue that, based on edge avoidance behavior, “grassland-interior” species such as the Henslow's Sparrow respond to edge effects mainly by a decrease in density, whereas habitat generalists such as the Dickcissel are affected mainly by a decrease in nesting success.
Activity Patterns of Marbled Murrelets in Douglas-Fir Old-Growth Forests of the Oregon Coast Range
Authors: Jodice Patrick G. R. , Collopy Michael W.
Published: September 2019

We monitored activity patterns of Marbled Murrelets (Brachyramphus marmoratus) on a near-daily basis using audio-visual surveys during three breeding seasons at five forest stands in the Oregon Coast Range. Three measures of activity were recorded: number of daily detections, number of daily vocalizations, and duration of daily activity. Each measure was highly variable within and among stands and years, and we recorded greater variability than has been previously reported for this species. The three measures of activity were strongly correlated within a day at each survey station, but correlative relationships at temporal and spatial scales greater than this were inconsistent. Activity varied greatly from one day to the next during all portions of the breeding season, and we did not identify any month when variability in activity was consistently higher or lower than any other month. Multivariate analyses revealed that weather and date variates explained little of the variability in daily activity. Given the extreme levels of variability in Marbled Murrelet activity and our lack of understanding as to which factors drive that variability, it is critical that conclusions about activity or behavior not be drawn from data sets not specifically designed to answer the questions of interest.
Patterns of Nest Attendance in Female Wood Ducks
Authors: Manlove Chad A. , Hepp Gary R.
Published: September 2019

We examined sources of variation in incubation patterns among female Wood Ducks (Aix sponsa), and investigated the effect of female nest attentiveness on incubation period. Data were collected from 44 females (n = 911 days) using temperature data loggers to monitor nest attendance throughout incubation. Mean (± SE) incubation constancy was 86.9 ± 0.6% and incubation period averaged 30.9 ± 0.2 days. Females took an average of two bimodally-distributed recesses per day. Duration of recesses averaged 98.6 ± 3.4 min, but were shorter in the morning than in mid-day or late afternoon. Body mass of incubating females declined 0.68 ± 0.2 g day−1, but there was no relationship between constancy and early incubation body mass or weight change of females. Incubation constancy was not correlated with length of the incubation period. For most females, incubation constancy and recess frequency did not change as incubation progressed. The fact that incubating females only lost an average of 3% of body mass, and constancy was not related to either body mass or length of the incubation period, suggests that females were not constrained energetically. Finally, we propose that the combination of reduced predation risk and the need of neonates to be more functionally mature at hatching has selected for longer incubation periods in Wood Ducks and other cavity-nesting waterfowl.
The Thermal Regime of Eggs During Laying and Incubation in Greater Snow Geese
Authors: Poussart Catherine , Larochelle Jacques , Gauthier Gilles
Published: September 2019

Dummy eggs were added to naturally incubated clutches of Greater Snow Geese (Chen caerulescens atlantica), an arctic-nesting species, in order to evaluate egg temperature during laying and incubation, and factors influencing egg cooling rate during female recesses. As laying progressed, both nest attentiveness by females and egg temperature progressively increased. Although the time spent at nest after laying the penultimate egg was relatively high (69% vs. 91% during incubation), mean egg temperature was still 5.7°C lower than during the early incubation period. This suggests that little embryonic development began before clutch completion. Thereafter, egg temperature averaged 37.1 ± 0.1°C during periods where females were present, a value that decreased only slightly when incubation recesses are included (36.8°C). This is a high temperature in comparison to other arctic-nesting geese. A modest increase (1.7°C) in mean egg temperature was observed as incubation progressed, but egg temperature was not influenced by clutch size or by the laying date of the first egg. During recesses lasting 24.7 ± 1.3 min on average, egg temperature dropped by 2.8 ± 0.3°C, at an instantaneous rate of 0.23 ± 0.02°C hr−1 °C−1. Cooling rates increased under windy conditions and decreased with high solar radiation, but were little affected by air temperature.
Characteristics of Predators and Offspring Influence Nest Defense by Arctic and Common Terns
Authors: Whittam Rebecca M. , Leonard Marty L.
Published: September 2019

Nest defense is a critical aspect of parental care that entails both costs and benefits. The purpose of this study was to examine patterns of nest defense in a colony of Arctic and Common Terns (Sterna paradisaea and S. hirundo, respectively) using observations of natural predators: Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus). Tern nest-defense scores were higher for hunting gulls than for overflying gulls and for gull flights closer to the ground. Defense scores also were significantly higher during the chick stage than during the egg stage. Within the chick stage, response score initially increased with age, but then declined. The results of this study indicate that terns vary their defense in relation to characteristics of predators and offspring that influence the costs and benefits of defense.
Nesting Success of Forest Birds in Southeast Alaska and Adjacent Canada
Authors: Willson Mary F. , Gende Scott M.
Published: September 2019

Predation caused 78% of nest failures in coastal forests of southeast Alaska and interior forests of adjacent Canada. Nest success tended to be better in coastal than interior forests. Mayfield daily nest survival from predation on open-cup nests was higher in egg than nestling phase for most species. Species building large (thrush-sized) nests had lower Mayfield daily survival from predation than species building smaller (warbler-sized) nests, but there was no difference in daily survival (total and from predation only) among species nesting in different vegetation strata. Nesting success differed little with nest cover or nest site diversity for most species. Total nest success within species was only sometimes higher in commonly used nest sites than in less frequently used sites. Nest survival from predation did not generally decrease with increasing nest density within guilds of species with similar nests or with nest-site similarity. We emphasize the likelihood of varied outcomes of natural selection on nest-site selection in differing circumstances.
Predation on Japanese Quail vs. House Sparrow Eggs in Artificial Nests: Small Eggs Reveal Small Predators
Authors: Maier Thomas J. , DeGraaf Richard M.
Published: September 2019

Nest predation studies frequently use eggs such as Japanese Quail (Coturnix japonica) to identify potential predators of Neotropical migrants' eggs, but such eggs may be too large or thick-shelled to identify the full complement of potential predators. We compared predation events and predators of Japanese Quail and smaller House Sparrow (Passer domesticus) eggs in paired, camera-monitored ground nests within edges and interiors of 40 mixed-hardwood forest stands in central Massachusetts. House Sparrow eggs were depredated significantly more than Japanese Quail eggs at both forest edges and interiors. Eleven potential predator species disturbed nests, six of which were confirmed as predators. Our use of House Sparrow eggs revealed predation by eastern chipmunks (Tamias striatus) and Black-capped Chickadee (Poecile atricapillus), but not by white-footed mice (Peromyscus leucopus), the most abundant small mammal species in all 40 stands. Neither predator species composition (as detected by camera) nor the frequency of nest predation differed between forest edge and interior. We conclude that the egg type used in artificial nest studies affects both the predation rates and the predator species detected.
Costs of Parasitism Incurred by Two Songbird Species and Their Quality as Cowbird Hosts
Authors: Burhans Dirk E. , Thompson Frank R. , Faaborg John
Published: September 2019

We measured the costs of Brown-headed Cowbird (Molothrus ater) parasitism incurred by Field Sparrows (Spizella pusilla) and Indigo Buntings (Passerina cyanea). We predicted that the frequent occurrence of nest desertion as a response to cowbird parasitism in Field Sparrows would be reflected by a higher cost of parasitism for that species. We also compared growth and survival of cowbird nestlings between hosts, predicting that they would do poorly at Field Sparrow nests because the latter appear to be avoided by cowbirds. Both species experienced reduced body mass gain in parasitized broods, but only Indigo Bunting suffered reduced tarsus growth. Both species experienced reductions in clutch size, hatching success, and nestling survival due to parasitism, but these losses did not differ among the two hosts. Multiple parasitism did not affect hatching success or nestling survival more than single parasitism for Indigo Buntings. Once accepted, cowbird offspring fared equally well in nests of both species, but almost half of all cowbird eggs laid in Field Sparrow nests were lost through nest abandonment. As parasitism costs to both species appear to be substantial, the rarity of nest desertion in Indigo Buntings may be due to other factors. Infrequent parasitism of Field Sparrows is consistent with host avoidance by cowbirds but other explanations should be explored.
Demography of Zenaida Doves in Puerto Rico
Authors: Rivera-MilÁn Frank F. , VÁzquez Myrna
Published: September 2019

We conducted a capture-recapture study of Zenaida Doves (Zenaida aurita) in three neighboring dairy farms in eastcentral Puerto Rico during 1984–1997. During 46 sampling periods, mean survival rate per sampling period was 0.77 (range = 0.1–1.0), mean recruitment was 911 individuals (range = 182–5,124), and mean population size was 1,569 individuals (range = 233–7,354). Survival increased during 1984–1991 and decreased during 1992–1997. Recruitment did not show a trend, but population size increased during 1984–1997. Rate of increase was a curvilinear decreasing function of population size. A demographic model with a fixed mortality rate stabilized at 1,350 individuals. When mortality rate was defined as a normal random variable, mean population size was 1,421 individuals, and there was a 0.95 probability of observing population sizes from 467 to 2,375 individuals. The size of the Zenaida Dove population varied widely over time, but periods of high recruitment rapidly offset periods of low survival in the dairy farms.
Stress, Corticosterone, and Heterophil to Lymphocyte Ratios in Free-Living Adélie Penguins
Authors: Vleck Carol M. , Vertalino Nicole , Vleck David , Bucher Theresa L.
Published: September 2019

We measured corticosterone in plasma collected from free-living Adélie Penguins (Pygoscelis adeliae) and made blood smears to count the ratio of heterophils to lymphocytes (H/L). Our objective was to categorize how these two measures of stress vary with potential stressors in the birds' environment. In penguins that were repeatedly sampled from three to eight times, repeated handling did not affect corticosterone levels or H/L, but there were significant differences among individuals. Nesting stage did not affect corticosterone level, but H/L was significantly lower during the chick stage than in the courting or incubation stages. Sex and handling times of less than 5 min had no effect on either corticosterone or H/L. In birds that had fasted up to 40 days during the courtship and early incubation stages, there was no increase in corticosterone or H/L with length of fasting, but in birds that had fasted more than 50 days, corticosterone levels increased. Birds with obvious injuries had significantly higher H/L than birds that had recently engaged in fights or those caring for chicks, but corticosterone levels did not differ in these groups. In free-living birds, H/L ratios provide a measure of stress that may be more useful than a single measure of plasma corticosterone in assessing response to chronic stressors like injury or crowded conditions in the breeding colony.
Marine Bird Attraction to Thermal Fronts in the California Current System
Authors: Hoefer Christopher J.
Published: September 2019

I relate marine bird density to the 55 strongest thermal fronts encountered during a survey of much of the eastern portion of the California Current and the adjacent coastal upwelling region. Elevated densities were recorded for all marine bird taxa except the Leach's Storm-Petrel (Oceanodroma leucorhoa). The variance explained by the regression models ranged from 3% for the Leach's Storm-Petrel to 85% for all marine birds. The response observed is notably stronger than previous analyses with similar data.
An Unusual Type of Sibling Aggression in Black-Crowned Night Herons
Authors: Medeiros Matthew J. , Emond Emily E. , Ploger Bonnie J.
Published: September 2019

Sibling aggression varies with brood size, nestling age disparities, and food characteristics. We observed feeding and fighting within two broods of Black-crowned Night Herons (Nycticorax nycticorax) in Minnesota. In one nest, on two different days, a senior chick swallowed the head of its smallest sibling, immobilizing it until it seemed near death. Occasional fights also occurred in this nest only. Senior chicks in both nests gained more food than juniors. We discuss possible functions of head-swallows, including how this behavior, as well as fighting and other factors, may have enhanced the feeding advantage of seniors.
Flight Costs and Fuel Composition of a Bird Migrating in a Wind Tunnel
Authors: Klaassen Marcel , Kvist Anders , Lindström Åke
Published: September 2019

We studied the energy and protein balance of a Thrush Nightingale Luscinia luscinia, a small long-distance migrant, during repeated 12-hr long flights in a wind tunnel and during subsequent two-day fueling periods. From the energy budgets we estimated the power requirements for migratory flight in this 26 g bird at 1.91 Watts. This is low compared to flight cost estimates in birds of similar mass and with similar wing shape. This suggests that power requirements for migratory flight are lower than the power requirements for nonmigratory flight. From excreta production during flight, and nitrogen and energy balance during subsequent fueling, the dry protein proportion of stores was estimated to be around 10%. A net catabolism of protein during migratory flight along with that of fat may reflect a physiologically inevitable process, a means of providing extra water to counteract dehydration, a production of uric acid for anti-oxidative purposes, and adaptive changes in the size of flight muscles and digestive organs in the exercising animal.
Foraging Distances of Radio-Marked Marbled Murrelets from Inland Areas in Southeast Alaska
Authors: Whitworth Darrell L. , Nelson S. Kim , Newman Scott H. , Van Vliet Gustaaf B. , Smith Winston P.
Published: September 2019

We radiotagged seven female and two male Marbled Murrelets (Brachyramphus marmoratus) of undetermined breeding status and followed their movements through the inner passages of northern southeast Alaska during the breeding season (May–July) in 1998. Six of the nine murrelets were detected inland in the early morning hours from 24 June to 17 July. Inland visits for each individual were consistent to a particular location, but short in duration, which precluded locating nest sites. We recorded 46 locations at sea up to 124 km (x̄ = 78 ± 27 km) from inland sites during the period 19 June to 16 July. We detected murrelets at inland sites and at sea on the same day on 20 occasions with a mean distance between these locations of 75 ± 42 km. The majority of murrelets were located at sea in western Icy Strait, a productive feeding area at the mouth of Glacier Bay, Alaska. This study provides the first direct evidence that Marbled Murrelets in southeast Alaska are consistently traveling considerable distances between potential nesting and foraging areas. These findings have important implications for murrelet conservation and management efforts in southeast Alaska.
Plumage Brightness and Breeding-Season Dominance in the House Finch: A Negatively Correlated Handicap?
Authors: McGraw Kevin J. , Hill Geoffrey E.
Published: September 2019

A variety of observations indicate that the carotenoid-based coloration of male House Finches (Carpodacus mexicanus) is an honest signal of quality. Plumage redness in this species positively reveals male nutritional condition, over-winter survival, and nest attentiveness. As a result, in the breeding season, male House Finches with brighter ornamental plumage are preferred by females as social mates over males with drabber plumage. In the nonbreeding season, however, bright red plumage does not seem to confer an advantage in aggressive interactions, as males with drabber plumage tend to dominate males with brighter plumage. We investigated this apparent paradox by conducting a breeding-season dominance experiment using captive males. We paired unfamiliar males of contrasting plumage brightness in a series of dominance trials during the breeding season and found that drabber males were dominant to brighter males in competition for access to food. Furthermore, in two captive flocks of males, plumage brightness was significantly negatively associated with social dominance. Although we have no conclusive evidence to explain why drab male House Finches are dominant to bright males throughout the year, we believe that motivational asymmetry may contribute to the observed negative correlation between signal intensity and signaler quality (“negatively correlated handicap”). Drab males may be more willing to compete for access to food or to females than are bright males because of the nutritional and/or mating disadvantages from which they suffer.
Measuring Annual Reproductive Success in Birds
Authors: Murray Bertram G.
Published: September 2019

From simulated data on three populations, I calculate different measures of “reproductive success”: clutch size, egg success (the proportion of eggs that produce young), nest success (the proportion of clutches that produce young), and the annual reproductive success per female in terms of both number of broods and number of young reared successfully during a breeding season. These measures of success are not correlated. Differences in egg success or nest success do not necessarily translate into differences in annual reproductive success, and differences in annual reproductive success do not necessarily translate into evolutionary success.
Inbreeding Depression and its Effects on Natal Dispersal in Red-Cockaded Woodpeckers
Authors: Daniels Susan J. , Walters Jeffrey R.
Published: September 2019

Natal dispersal is a key life-history component that may be influenced by the fitness consequences of inbreeding. We studied natal dispersal and inbreeding within a large population of cooperatively breeding, endangered Red-cockaded Woodpeckers (Picoides borealis). We assessed the costs of close inbreeding, the spatial distribution of related males and its relationship to dispersal distance of females, and the change in dispersal behavior of females in the presence of closely related males. Close inbreeding resulted in a significant loss of fitness, through two separate effects: closely related pairs (kinship coefficient ≥ 0.125) exhibited lowered hatching rates and lowered survival and recruitment of fledglings relative to unrelated pairs. Despite a highly predictable spatial clustering of closely related males near the female's natal territory, natal dispersal distance of females was not sufficient to avoid these males as mates. Females changed dispersal behavior in the presence of closely related males on the natal territory: female fledglings were significantly more likely to disperse from natal territories if there were closely related males breeding there in the following year. Females did not change dispersal behavior in the presence of related males that were not on the natal territory. We suggest that dispersal behavior is a trade-off between benefits of short-distance dispersal, e.g., an advantage in competing for scarce breeding vacancies, and the substantial cost of close inbreeding.
Natal Dispersal in the Cooperatively Breeding Acorn Woodpecker
Authors: Koenig Walter D. , Hooge Philip N. , Stanback Mark T. , Haydock Joseph
Published: September 2019

Dispersal data are inevitably biased toward short-distance events, often highly so. We illustrate this problem using our long-term study of Acorn Woodpeckers (Melanerpes formicivorus) in central coastal California. Estimating the proportion of birds disappearing from the study area and correcting for detectability within the maximum observable distance are the first steps toward achieving a realistic estimate of dispersal distributions. Unfortunately, there is generally no objective way to determine the fates of birds not accounted for by these procedures, much less estimating the distances they may have moved. Estimated mean and root-mean-square dispersal distances range from 0.22–2.90 km for males and 0.53–9.57 km for females depending on what assumptions and corrections are made. Three field methods used to help correct for bias beyond the limits of normal study areas include surveying alternative study sites, expanding the study site (super study sites), and radio-tracking dispersers within a population. All of these methods have their limitations or can only be used in special cases. New technologies may help alleviate this problem in the near future. Until then, we urge caution in interpreting observed dispersal data from all but the most isolated of avian populations.
Recruitment, Dispersal, and Demographic Rescue in Spatially-Structured White-Tailed Ptarmigan Populations
Authors: Martin Kathy , Stacey Peter B. , Braun Clait E.
Published: September 2019

We studied recruitment and dispersal of White-tailed Ptarmigan (Lagopus leucurus) breeding in naturally fragmented alpine habitats at four study sites in Colorado from 1987–1998. Almost all recruitment for both sexes, particularly females, was of birds produced outside local populations and also external to nearby studied populations. Populations were more dependent on female recruitment than on male recruitment to sustain them, and patterns of recruitment were not correlated with local survival of adults or production of young the previous year, except at one site for females. Over 95% of recruits were yearlings. Breeding dispersal of adults, an infrequent but regular event, was also important to inter-population connectivity. Our data for multiple populations allowed us to describe movement patterns among populations to assess consistency with conditions required for a rescue system. After widespread reproductive failure in one year, we expected all populations the next year would have low recruitment due to a reduced supply of recruits produced in the region. Recruitment was low, but impact varied among populations. We conducted an over-winter study of radio-marked offspring to determine possible influences of winter site location and relatives on recruitment patterns. Contrary to expectation, offspring remained on or near breeding sites in winter, but were not located near their mothers or siblings. Recruitment location was related to winter site location. White-tailed Ptarmigan exhibit a well developed capacity for external recruitment that allows them to persist in small populations with stochastic conditions for breeding and survival. Extensive external recruitment may be a general pattern for birds.