bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship Between Mayfield Nest-Survival Estimates and Seasonal Fecundity: A Cautionary Note
Authors: Jones Jason , Doran Patrick J. , Nagy Laura R. , Holmes Richard T.
Published: September 2019

Estimates of nest survival are commonly used as indices of reproductive productivity in a wide range of studies, including examinations of population dynamics, habitat fragmentation, and wildlife management. However, the strength of the relationship between estimates of nest survival and of seasonal fecundity has rarely been tested. To examine that relationship, we used 16 years of demographic data from an intensively studied population of individually marked Black-throated Blue Warblers (Dendroica caerulescens). We found a positive relationship between Mayfield nest-survival estimates and seasonal fecundity (i.e. number of fledglings produced per female). However, seasonal-fecundity predictions based on nestsurvival values underestimated observed seasonal fecundity by an average of 33% and population growth rate by 20%. Our results suggest that, though nest-survival estimates may be useful as indices of pressures on a population (e.g. nest predation), care is needed in using them as the basis of conservation or management strategies or to make inferences about population-level processes.

Relación entre las Estimaciones de Supervivencia de Nidos de Mayfield y la Fecundidad Estacional: una Nota de Cautela
Is Nest Predation by Steller's Jays (Cyanocitta Stelleri) Incidental or the Result of a Specialized Search Strategy?
Authors: Vigallon Stacey M. , Marzluff John M.
Published: September 2019

Decreased nest success and elevated levels of nest predation have been linked to changes in landscape configuration and increased edge. However, our current understanding of the mechanics of nest predation is limited. Using radiotelemetry and artificial nest experiments, we studied the ranging and nest-predation behavior of the Steller's Jay (Cyanocitta stelleri) in the managed forests of western Washington. Steller's Jays used a variety of forest seral stages, 95% of foraging observations occurred within 50 m of edges, and home range did not appear to be influenced by breeding success. Predation on artificial nests was elevated in high-use areas of home ranges, which suggests that Steller's Jays find nests incidentally while foraging for primary prey (insects). Steller's Jays did not appear to use a specialized search strategy to find nests, though they had a search image for nests and were capable of performing area-restricted searching for other food items (peanuts). To assess the risk of nest predation by Steller's Jays, it may be useful for managers to survey areas of concern for Steller's Jays and their foods. By equating relative abundance of Steller's Jays with nest predation risk, managers can then map predation risk onto the landscape of concern at the scale of the management unit.

¿Es la Depredación de Nidos por Cyanocitta stelleri Incidental o es el Resultado de una Estrategia de Búsqueda Especializada?
Protogyny in Autumn Migration: Do Male Birds ”Play Chicken”?
Authors: Mills Alexander M.
Published: September 2019

Protandry, the earlier arrival of males than of females on breeding areas, occurs in many taxa, including many migratory birds. Numerous hypotheses have been generated to explain protandry. Using bird-banding records, I show that protogyny, the earlier migration of females, frequently occurs in the autumn, though it is less universal and less dramatic than spring protandry. In one species, it occurs in both hatch-year and adult birds. When (1) spring and autumn, (2) departures and arrivals, and (3) breeding and wintering ground conditions are considered, hypotheses generated only to explain spring protandry can be more thoroughly evaluated. Using that approach, the most parsimonious explanation of differential migration between the sexes explains earlier male arrival in spring and later male departure in autumn through either (1) indirect selection operating on intrasexual male competition for territories or (2) direct selection operating on intersexual relations requiring males to be present on breeding territories when females are present. In autumn-protogynous species, males may ”play chicken,” balancing the benefits of remaining longer than females and protecting territories for subsequent years against the costs of remaining in the north under deteriorating conditions and delaying the acquisition of a good winter territory.

Protogynie et migration automnale: Est-ce que les mâles ”jouent les dégonflés”?
Mitochondrial Variation in Bolivian Populations of the Variable Antshrike (Thamnophilus Caerulescens)
Authors: Brumfield Robb T.
Published: September 2019

The Variable Antshrike (Thamnophilus caerulescens) is arguably the most polytypic thamnophilid, with males ranging from almost entirely jet black to nearly white. The four subspecies that occur in Bolivia are strikingly divergent in male plumage: T. c. aspersiventer (black with white-barred belly), T. c. connectens (black back and bib with white belly), T. c. dinellii (gray throat and back with rufous belly), and T. c. paraguayensis (light gray with white belly). To assess the genetic structure of those taxa in Bolivia, sequence variation at the mitochondrial cytochrome-b gene was screened in 126 individuals collected across transects spanning the plumage and vocal variation in the four forms. A 95-km-wide cline in haplotype frequencies from T. c. aspersiventer to T. c. dinellii was centered in the Serrania Cochabamba across an ecotone from humid to dry Andean foothill habitats. Thamnophilus caerulescens connectens is not a valid taxon, instead representing an introgressed population near the dinellii tail of the T. c. aspersiventer-T. c. dinellii hybrid zone. Although direct contact between T. c. dinellii and T. c. paraguayensis remains undocumented, the mitochondrial data were consistent with introgression along a broad cline extending across most of southern Bolivia. Overall, the transitions in mitochondrial frequencies were remarkably concordant with clinal changes in vocalizations among those same populations (Isler et al. 2005). Both studies highlight the need for increased sampling, in both the geographic extent and number of individuals per population, to address adequately the potential for clinal variation between populations that are not isolated geographically. A more restricted sampling design in the present study might have led to the erroneous conclusion that T. c. aspersiventer, T. c. dinellii, and T. c. paraguayensis have reciprocally monphyletic mitochondrial lineages, making them full species according to some species concepts.
Burrowing Owl (Athene Cunicularia) Population Genetics: A Comparison of North American Forms and Migratory Habits
Authors: Korfanta Nicole M. , McDonald David B. , Glenn Travis C.
Published: September 2019

We assessed the effects of range disjunction, migratory habit, coloniality, and habitat structure on the genetic differentiation of North American Burrowing Owl (Athene cunicularia) populations. Burrowing Owls in North America comprise two forms or subspecies: A. c. floridana in Florida, separated by ∼1,500 km from the western form, A. c. hypugaea, which ranges from Texas to California and north to southern Canada. Burrowing Owls tend to be loosely colonial, and both the Florida populations and southerly populations of A. c. hypugaea from California to Texas are nonmigratory. To assess genetic structure, we examined 201 individuals from nine western and six Florida populations at seven highly variable microsatellite DNA loci. Mean gene diversity (Hexp) was higher in the west than in Florida (0.539 and 0.341, respectively; P < 0.05). Populations within subspecies were essentially panmictic (A. c. floridana: θ = 0.038, ρ = 0.014; A. c. hypugaea: θ = 0.014, ρ = 0.009) and even genetic differentiation across subspecies was modest (θ = 0.051, ρ = 0.014). Nevertheless, the western and Florida forms were easily distinguished by any of several criteria, such as allelic absences in Florida, assignment tests, and well-supported branches on the inferred phylogenetic tree. Genetic differentiation was at least twice as great in resident Florida (θ = 0.038) and California (θ = 0.021) populations as in migratory western populations (θ = 0.012), though 95% confidence intervals of theta estimates overlapped. We found no evidence of a genetic bottleneck that would result in evolutionary disequilibrium within subspecies. In the west, high observed heterozygosity values and evidence of gene flow suggest that population declines and patchy habitat, which currently imperil this species throughout much of its range, have not led to inbreeding or biologically meaningful genetic differentiation among the sampled populations.
Survival of Young Greater Snow Geese (Chen Caerulescens Atlantica) During Fall Migration
Authors: Menu Stéphane , Gauthier Gilles , Reed Austin
Published: September 2019

The many hazards that await birds along their migratory routes may negatively affect their survival, especially among newly fledged young. We estimated survival of young Greater Snow Geese (Chen caerulescens atlantica) during fall migration from the High Arctic to temperate areas and examined factors affecting their survival over a five-year period, using two approaches. First, each year (1993–1997), we banded fledglings and adults in mid-August, just before their departure from Bylot Island in the High Arctic (Nunavut, Canada), and again at an important staging area 3,000 km to the south at the Cap Tourmente National Wildlife Area (Québec, Canada) in October; recovery data from those two banding periods allowed estimation of survival during fall migration. Second, we visually determined brood size of neck-banded females before and after the main portion of the migratory flight, to estimate survival of young. The two approaches yielded similar survival estimates and showed the same interannual variation, thus suggesting that estimates were reliable. Mortality of young shortly after fledging and during the fall migration was high, compared with that of adults (monthly survival 0.662 in young vs. 0.989 in adults). However, mortality of young after migration was similar to that of adults (monthly survival 0.969 in young vs. 0.972 in adults). Migration survival of young varied considerably among annual cohorts (range of 0.119–0.707 over five years), and most of the mortality appeared to be natural. Survival was especially low in years when (1) temperatures at time of fledging and start of migration were low (i.e. near or below freezing), (2) mean body mass of goslings near fledging was low, or (3) mean fledging date was late. Our results suggest that migration survival of young is affected by a combination of several factors (climatic conditions, body mass, and fledging date) and that survival is reduced when one of those factors intervenes.
Effects of Environmental Conditions and Parental Quality on Inter- and Intraclutch Egg-Size Variation in the Collared Flycatcher (Ficedula Albicollis)
Authors: Hargitai Rita , Török János , Tóth László , Hegyi Gergely , Rosivall Balázs , Szigeti Beáta , Szöllősi Eszter
Published: September 2019

Egg size is a particularly important life-history trait mediating maternal influences on offspring phenotype. Females can vary their egg-size investment in relation to environmental circumstances, their own breeding condition, and the quality of their mate. Here we analyzed inter- and intraclutch variation in egg size in the Collared Flycatcher (Ficedula albicollis) on the basis of eight years of data. According to our results, mean egg size increased with female condition, but did not differ among young, middle-aged, and old females. The male’s age, body size, and forehead patch size did not influence egg size; thus, we found no evidence for differential investment in egg size in relation to male quality. We found no effect of laying date on egg size when controlling for ambient temperature during the egg formation period, yet temperature had a significant effect on egg size. That result indicates proximate constraints on egg formation. Furthermore, we report on annual differences in intraclutch egg-size variation. Egg size increased within clutches in years with a warm prelaying period; whereas in years when the weather during that period was cold, there was no significant intraclutch trend. Proximate considerations seem to explain the observed patterns of intraclutch egg-size variation; however, we cannot reject the adaptive explanation. Mean egg size and intraclutch egg-size variation were unrelated to clutch size. Therefore, we found no evidence for a trade-off between size and number of eggs within a clutch.
Effects of Water Salinity on Growth and Survival of Common Eider (Somateria Mollissima) Ducklings
Authors: DeVink Jean-Michel A. , Gilchrist H. Grant , Diamond Antony W.
Published: September 2019

The need for fresh water may affect growth and survival of young waterfowl, including ducklings of sea ducks that are routinely raised in coastal marine habitats. We studied the influence of water salinity on growth and survival of Common Eider (Somateria mollissima) ducklings collected from nests on Southampton Island, Nunavut, Canada, in July 2001 and 2002. In 2001, 50 ducklings were partitioned into five groups (n = 10) and assigned a water salinity treatment for 6.5 days. Treatments included fresh water (<1 ppt NaCl), brackish water (11 ppt or 21 ppt), seawater (33 ppt), and a mixed regime (<1 ppt for 12 h, followed by 33 ppt for six days). In 2002, the experiment was replicated twice with different ducklings. Overall, growth rates were negatively correlated, and mortality rates positively correlated, with water salinity: 3%, 17%, and 60% of ducklings died in the <1-ppt, 11-ppt, and 21-ppt treatment groups, respectively; and 100% died in the 33-ppt and mixed-regime groups. The results confirm that fresh water is required for growth and survival of Common Eider ducklings immediately after hatch, which suggests that sources of fresh water in brood-rearing areas are an important requirement for successful reproduction.
Host Recognition of Brood Parasites: Implications for Methodology in Studies of Enemy Recognition
Authors: Grim Tomáš
Published: September 2019

Various studies have shown that experiments on nest defense and enemy recognition (e.g. recognition of adult brood parasites) can be confounded by many factors. However, no study has described a confounding effect of control dummy type. Here, I show experimentally that the choice of control dummy may influence the results of an experiment and lead to erroneous conclusions. I tested recognition abilities of the Blackcap (Sylvia atricapilla), currently a host rarely used by the Common Cuckoo (Cuculus canorus). Blackcaps responded very differently to two kinds of control dummies: they ignored the Eurasian Blackbird (Turdus merula) dummy, but attacked the Rock Pigeon (Columba livia) dummy as frequently as they attacked the Common Cuckoo. The differing results may be explained by the fact that the Rock Pigeon is more similar to the Common Cuckoo than the Eurasian Blackbird is, and consequently elicited more aggressive behavior than the latter. Thus, absence of discrimination in enemy-recognition studies may reflect a methodological artifact resulting from varying abilities of particular hosts to discriminate along a continuum of recognition cues. This result has serious methodological implications for further research on enemy recognition and aggression in general: a control dummy should not be too similar to the dummy brood parasite; otherwise, the chance of detecting existing recognition abilities is low. Further, I argue that coevolution only increases pre-existing aggression in the particular host species. Therefore, increment analysis (assessing changes in host antiparasitic responses during the nesting cycle while controlling for background aggression to control dummies) provides a more accurate picture of hosts' recognition abilities than the traditional approach (when the total level of antiparasitic response is analyzed).
Fat-Deposition Strategies Among High-Latitude Passerine Migrants
Authors: Benson Anna-Marie , Winker Kevin
Published: September 2019

We studied fat stores in passerine migrants at a high-latitude site in Fairbanks, Alaska (64°50'N, 147°50'W). We examined fat-deposition strategies during the final (spring) and initial (autumn) stages of long-distance migration, 1992–1998, to (1) improve understanding of geographic fat-deposition patterns by adding a high-latitude perspective; (2) determine whether there are age-related differences in fat-deposition strategies in autumn; and (3) test the “spring fatter” hypothesis of seasonal fat-deposition, which suggests that migrants should carry more fat in spring when they near their breeding areas than in autumn when they depart. Our analyses examined factors affecting daily fat scores during migration and compared between-season differences in fat stores among a total of 18,685 individuals of 16 migrant species. In autumn, adults had higher visible subcutaneous fat scores than immatures in 11 of 16 species. However, in all but two species, those differences were attributable to the effects of overnight low temperature, day length, and time of day, rather than age, probably because of later departures by adults. Fat scores were higher in autumn than in spring in 6 of 16 species, and body-condition indices were higher in autumn in 5 of 16 species. Only one species showed higher fat scores in spring, but that difference was not reflected in a seasonal comparison of body- condition indices. No species arrived with high fat loads in spring, and generally low fat levels in autumn suggest that high-latitude passerine migrants in North America are paying most of the energetic costs of long-distance migration with resources obtained en route to their wintering grounds. Among passerine migrants near these high-latitude breeding grounds, seasonal fat-deposition strategies appear to be responding to energetic needs at the level of daily maintenance, rather than to hypothesized insurance needs in spring or to the forthcoming needs of a long- distance migration in autumn.
Male Reproductive Success is Correlated With Blood Parasite Levels and Body Condition in the Promiscuous Aquatic Warbler (Acrocephalus Paludicola)
Authors: Dyrcz Andrzej , Wink Michael , Kruszewicz Andrzej , Leisler Bernd
Published: September 2019

The Aquatic Warbler (Acrocephalus paludicola) has a unique mating system. Males are free of any parental duties and can fertilize many females during a single breeding season. Females also usually copulate with more than one male, and nestlings in a single nest may be sired by as many as five males. Paternal success of 33 Aquatic Warbler males in a Polish population was determined by microsatellite polymerase-chain-reaction analysis. Males infected by blood parasites (trypanosomes) sired fewer offspring, weighed less, and probably arrived later to breeding grounds than uninfected males. Number of nestlings sired by a male correlated positively with its fat deposits and wing length. These findings indicate that male body condition directly influences paternal success. Number of sired nestlings per individual male ranged from one to eight. Reproductive success among males was uneven, with six males (18%) fathering 44% of nestlings in the study area. Males with high reproductive success arrived at the breeding grounds earlier in spring than males with low reproductive success.
Song Structure and Microgeographic Song Variation in Wedge-Tailed Sabrewings (Campylopterus Curvipennis) in Veracruz, Mexico
Authors: González Clementina , Ornelas Juan Francisco
Published: September 2019

We studied the songs of Wedge-tailed Sabrewings (Campylopterus curvipennis) in six localities from central Veracruz, Mexico, to document structure and variation within and between singing groups in the same geographic region. Wedgetailed Sabrewing songs were acoustically, structurally, and behaviorally complex, rivaling those of other taxa with complex signals. Songs of individual birds were composed of >45 well-differentiated and structurally complex syllables. We found 239 different syllable types across eight recorded singing groups of Wedge-tailed Sabrewings (∼20 syllable types per singing group), with the greatest versatility recorded in hummingbirds to date. The acoustic variation (15 variables) was summarized in three principal components (58% of acoustic variation), in which intragroup variability accounted for most of the observed variation. We found significant differences between and within groups in terms of syllable sharing (Jaccard’s similarity coefficient). Individuals generally shared >50% of syllable types within groups, whereas syllable sharing was <10% between individuals from different groups. The same microgeographic pattern was supported in a UPGMA (unweighted pair-group method with arithmetic mean) analysis where individual songs from each singing group clustered separately. However, songs recorded at the same location differed between seasons, which suggests that this species does not exhibit geographically distinct dialects that are consistent across time. The interplay among this species’ social system, distribution of its floral resources, and microgeographic and temporal variation of its song requires further research.
Phylogenetic Relationships of Antpitta Genera (Passeriformes: Formicariidae)
Authors: Rice Nathan H.
Published: September 2019

Phylogenetic relationships among the antpitta genera were studied using DNA sequence data from the mitochondrial genome. The clade representing the traditional “antpitta” genera (Grallaria, Grallaricula, Hylopezus, Myrmothera, and Pittasoma) was found to be paraphyletic, owing to the sister relationship of Pittasoma and Conopophaga. In a previously unreported relationship, Pittasoma was strongly supported as the sister genus to Conopophaga (Conopophagidae). The remaining antpitta genera form a fully resolved and well-supported monophyletic lineage with two major subclades. The first clade consists of the genus Grallaria and supports the subgenera identified by Lowery and O'Neill (1969). The second antpitta clade has Hylopezus as the sister genus to Myrmothera, with Grallaricula as their sister genus. The results here allow for a new interpretation of the morphological characters used in previous studies.
Additional Data on Mitochondrial DNA of North American Large Gull Taxa
Authors: Gay Laurène , Bell Douglas A. , Crochet Pierre-André
Published: September 2019

After publication of the Larus phylogeny in Crochet et al. (2002), the taxonomic status of the “Larus thayeri“ and the “L. occidentalis“ specimens that were used in that study came into question. For each of those species, we sequenced the same mitochondrial DNA regions in new specimens of known identity. In addition, specimens of L. glaucescens were included. Results from using those specimens confirm that L. occidentalis was the first to diverge from the large white-headed gulls. Larus glaucescens, on the contrary, is part of the Arctic species clade, which also includes L. hyperboreus, L. glaucoides, L. thayeri, and L. schistisagus. The three new L. thayeri specimens differ substantially in mitochondrial DNA from the previously used sample of L. thayeri and share the same haplotype with L. glaucescens. The significance of this finding is unclear, because relationships within the “Arctic species“ clade are still unresolved; that is attributable to the unusually high incidence of lineage sharing and extremely low divergence of haplotypes in the group.
The Birds of Hispaniola
Authors: Arendt Wayne J.
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.
Curassows and Related Birds
Authors: Brooks Daniel M.
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.
Insect and Bird Interactions
Authors: Cooper Robert J.
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.
Gulls of North America, Europe, and Asia
Authors: Jehl J. R.
Published: September 2019

The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists' Union.
Ultraviolet Degradation in Carotenoid Patches: Live Versus Museum Specimens of Wood Warblers (Parulidae)
Authors: McNett Gabriel D. , Marchetti Karen
Published: September 2019

Accurate assessment of color is essential in testing the adaptive significance of color variation in avian plumage. Over the past decade, use of objective methods for assessing color has increased, with particular emphasis on ultraviolet (UV) wavelengths. Researchers have used various source materials, most notably museum specimens, to extend or represent color measurements of individuals in natural populations. Here, we address whether the colors seen in museum specimens accurately represent the colors seen in natural populations. We focus on UV wavelengths and carotenoid-derived colors across 10 species of wood-warblers (Parulidae). Our results indicate an uneven decrease in brightness across the color spectrum, with greater relative decrease in shorter wavelengths in museum specimens. That decrease leads to differences in both hue and chroma between living and museum specimens. The difference from live specimens appears to increase with the museum specimen's age. Our results suggest that caution is needed when using data from museum specimens to test hypotheses on plumage coloration, particularly those involving communication.

Degradación Ultravioleta en Parches de Carotenoides: Especímenes Vivos versus Especímenes de Museo de Especies de la Familia Parulidae
Hippocampal Volume Does not Correlate With Food-Hoarding Rates in The Black-Capped Chickadee (Poecile Atricapillus) and Willow Tit (Parus Montanus)
Authors: Brodin Anders
Published: September 2019

Food-hoarding birds use memory to relocate caches, and species that store thousands of scattered food items must have an extraordinary memory capacity to be able to relocate them. Because the hippocampus is important in the functioning of spatial memory, it is logical to assume that the amount of food stored should correlate with hippocampal volume. Previously, food-hoarding capacity has been used as the predictor variable for hippocampal volume. Using the opposite approach, I tested whether hippocampal volume can be used to predict the amount of food stored. The atricapilla complex, a superspecies in the Paridae, has a wide Holarctic distribution, with the Black-capped Chickadee (Poecile atricapillus) in America and the Willow Tit (Parus montanus) in Eurasia. Although they live in similar ecological conditions, the Willow Tit possesses a hippocampus almost twice the size of the Black-capped Chickadee's. I sampled hoarding intensities in Black-capped Chickadees in British Columbia with the same methods I used previously in Willow Tits in Sweden. Contrary to expectation, Black-capped Chickadees stored at the same high rates as Willow Tits, which suggests that both species are large-scale hoarders. I discuss possible explanations for why the difference in hippocampal volume did not translate into differences in food-hoarding rates.

Le Volume de l'Hippocampe n'est pas Corrélé avec le Taux de Stockage de Nourriture Chez Poecile atricapillus et Parus montanus
Seasonal Decline in Leukocyte Concentrations and Reproductive Output in Female Great Tits (Parus Major)
Authors: Dubiec Anna , Witek Magdalena , Cichoń Mariusz
Published: September 2019

We studied the relationship between breeding parameters and leukocyte counts (number of cells in 1 mm3 of blood) in Great Tit (Parus major) females. To exclude potential effects on leukocyte concentration of high reproductive effort related to nestling provisioning, we collected blood samples from females at the end of their incubation period. Early-breeding females had greater blood counts of total leukocytes, lymphocytes, and heterophils than birds starting their clutches late in the season. Reproductive success, measured as the number of successfully fledged young, declined over the breeding season and showed no association with total leukocyte concentration. Number of leukocytes was not related to female condition measured as residuals from the regression of body weight on tarsus length. Moreover, the concentration of leukocytes did not predict the probability that a female would survive to the following breeding season.

Disminución Estacional en las Concentraciones de Leucocitos y en el Rendimiento Reproductivo en Parus major
Division of Labor: Incubation and Biparental Care in House Sparrows (Passer Domesticus)
Authors: Bartlett Terri L. , Mock Douglas W. , Schwagmeyer P. L.
Published: September 2019

In the great majority of animal taxa, males do not participate in parental care, but substantial paternal care is common across avian species. We examined male and female incubation contributions in House Sparrows (Passer domesticus), quantifying the incubation behavior of free-living, individually color-banded parents during 47 nesting cycles. We also measured the relative warmth of male and female incubation surfaces. Females spent more time incubating than their male partners, and female time incubating served as the best single predictor for hatching success. Considered alone, male time incubating correlated negatively with hatching success, but that effect was nullified when female incubation was taken into account. Females had warmer abdomens than males, a difference that may reflect greater development of brood patch and effectiveness of incubation in that sex. Here, male badge size was not demonstrably associated with either male or female incubation patterns or hatching success.

División de Labores: Incubación y Cuidado por Ambos Progenitores en Passer domesticus
Are Artificial Bird Nests Effective Surrogates for Estimating Predation on Real Bird Nests? A Test With Tropical Birds
Authors: Robinson W. Douglas , Styrsky Jennifer Nesbitt , Brawn Jeffrey D.
Published: September 2019

Artificial bird nests are often used in studying birds whose nests are difficult to find, such as those of many tropical species. Yet the underlying assumption that predation on artificial nests accurately estimates predation on real nests may be invalid. We compared rates at which contents of real and artificial nests were lost to predators in a Panamanian rainforest. We attempted to make artificial nests as realistic as possible by moving real, undamaged nests to species-typical nest sites in a study area where the same species were actively breeding. Characteristics of new sites for the moved nests were statistically similar to nest sites chosen by birds. We baited nests with two quail eggs and monitored them for species-specific incubation periods. Predation on real and artificial nests was dissimilar in three of four species, revealing that predation on artificial nests correlated poorly with predation on real nests. In a fourth species, artificial and real nests were lost at similar rates. The latter result may have occurred by chance, because depredated real nests rarely showed any sign of damage; whereas depredated artificial nests were torn, which suggests that real and artificial nests attracted different predators. Our results indicate that artificial nests, even when built by the species themselves and placed in realistic situations, are poor predictors of real nest success and we caution against their use in the tropics.

Son los Nidos Artificiales Sustitutos Efectivos para Estimar la Depredación de Nidos Verdaderos? Una Prueba con Aves Tropicales
To Double-Brood or not? Individual Variation in the Reproductive Effort in Black-Throated Blue Warblers (Dendroica Caerulescens)
Authors: Nagy Laura R. , Holmes Richard T.
Published: September 2019

Individuals within a population vary in important fitness components, such as reproductive success. In general, females can maximize the number of young they produce by altering either the number of young per breeding attempt or the number of breeding attempts per season. In short-lived species, and especially in small passerine birds, number of breeding attempts per season varies markedly among individuals. Here, we evaluated factors influencing whether female Blackthroated Blue Warblers (Dendroica caerulescens) initiated additional nests after a successful breeding attempt (i.e. double-brooded). The percentage of females that laid a second clutch after successfully fledging a first brood ranged from 0 to 87% and averaged 53% (n = 7 years). Multiple logistic regression and AICc model selection indicated that double-brooded females bred in territories with greater food availability and produced heavier nestlings than single-brooded females. Female age, male age, date of first breeding attempt, and number of young in the first clutch were not included in the best-fit model. Older females, however, produced heavier fledglings, and females mated to older males occurred on territories with greater food availability, indicating that age contributed to individual variation in reproductive output. Because the proportion of females that produce multiple broods within a season can have a substantial effect on the annual fecundity of a population, variation among females and among the territories they occupy (i.e. habitat quality) are key factors influencing population dynamics in this and other multibrooded, shortlived species.

Poner Nidadas Dobles o No? Variación Individual en el Esfuerzo Reproductivo en Dendroica caerulescens
A Tiny Barbet-Like Bird From the Lower Oligocene of Germany: The Smallest Species and Earliest Substantial Fossil Record of The Pici (Woodpeckers and Allies)
Authors: Mayr Gerald
Published: September 2019

Rupelramphastoides knopfi, a new genus and species of the Pici (barbets, woodpeckers, and allies), is described from Frauenweiler, a Lower Oligocene (30–34 mya) fossil site in Germany. The disarticulated skeleton of the new species constitutes the first associated remains of a fossil member of the Pici and is the smallest known species and earliest substantial fossil record of this taxon. Despite an overall resemblance to modern Ramphastidae, R. knopfi appears to be distinguished from crown group Pici by several plesiomorphic characteristics. It is classified “family incertae sedis,” pending discovery of additional, better-preserved specimens. The fossil record and geographic occurrence of the basal lineages within the crown group are in concordance with an Old World origin of the Pici. The reasons that led to extinction of tiny Pici in Europe remain uncertain, but food competition with passeriform birds during periods of limited food availability may have played a major role.

Ein winziger bartvogelähnlicher Vogel aus dem Unter-Oligozän Deutschlands: die kleinste Art und der älteste substantielle Fossilnachweis der Pici (Spechte und Verwandte)
Extrapair Fertilization in the Black-Browed Reed Warbler (Acrocephalus Bistrigiceps): Effects on Mating Status and Nesting Cycle of Cuckolded and Cuckolder Males
Authors: Hamao Shoji , Saito Daichi S.
Published: September 2019

We studied the relationship between the occurrence of extrapair fertilizations (EPFs) and mating status and nesting cycle of mates, respectively, in a population of Black-browed Reed Warblers (Acrocephalus bistrigiceps). Overall, 6.4% (9 of 140) of the chicks were sired by extrapair males, and 13.5% (5 of 37) of the broods contained at least one extrapair chick. Socially polygynous males were cuckolded more frequently than socially monogamous males (40.0% and 3.7%, respectively). In three of four cases where cuckolded males were polygynous, the fertile periods of their mates overlapped. Except for two floating males that obtained EPFs, five out of seven cuckolder males were paired. Males succeeded in EPFs when the fertile period of the extrapair females largely overlapped the incubation period of their own mates. These findings are consistent with the hypothesis that there are trade-offs between extrapair copulation activity and both mate guarding and rearing of nestlings.

Fertilisation Extraconjugale chez Acrocephalus bistrigiceps: Effets des Mâles Infidèles et Cocus sur le Statut de Couple et le Cycle de Nidification
Food Allocation in Collared Flycatcher (Ficedula Albicollis) Broods: Do Rules Change With The Age of Nestlings?
Authors: Rosivall Balázs , Török János , Szöllősi Eszter
Published: September 2019

Food allocation among nestlings has a strong influence on parental fitness. Maximizing fledging success in a favorable environment requires food distribution based on offspring need signals. However, food limitation, differences among individual nestlings in their quality, or variation in the costs of rearing different young may result in preferential allocation of food by parents. If signals of nestling quality or need change in meaning with age, parents are expected to adjust their feeding rules to those changes. We examined food allocation in broods of Collared Flycatchers (Ficedula albicollis), a sexually size-monomorphic passerine. In a multivariate analysis, we investigated the role of sex, size, condition, position, and begging intensity in two nestling ages. Size, condition, and sex of nestlings did not affect parental decisions. Begging intensity and nestling position, however, had a role in food allocation in both age categories. Both parents preferred the more intensely begging nestlings. Males did not show clear position preference in the “young” age category, but had preferred positions with older nestlings. Female position preference was observed in both age categories. Preferred positions of male and female parents differed; still, we observed overall position preference.

Asignación de Alimentos en Nidadas de Ficedula albicollis: ¿Cambian las Reglas con la Edad de los Pichones?
Long-Term Trends in Spring Arrival Dates of Migrant Birds at Delta Marsh, Manitoba, in Relation to Climate Change
Authors: Murphy-Klassen Heather M. , Underwood Todd J. , Sealy Spencer G. , Czyrnyj Ashleigh A.
Published: September 2019

We examined a 63-year data set of dates of first spring sightings for 96 species of migrant birds at Delta Marsh, Manitoba, and considered the influence of local climate change on those arrival dates. Mean monthly spring temperatures increased (0.6–3.8°C) for all four months considered; however, trends for February and March were stronger than those for April and May. Over the 63-year period, 27 species significantly altered their arrival dates. Most of those species arrived significantly earlier; whereas only two species, Greater Yellowlegs (Tringa melanoleuca) and Lesser Yellowlegs (T. flavipes), arrived significantly later over time. About half of the migrants showed significant relationships between arrival dates and mean temperature for their month of arrival. Fifteen species showed significantly earlier arrivals over time and a significant relationship between arrival date and temperature. We also characterized migrants by taxon, breeding status, and wintering location to determine whether there were any trends for altered arrivals within certain groups. Waterfowl, species that breed at Delta Marsh, and short-distance migrants showed slightly higher incidences of advancing arrival dates compared with other groups. Our results provide evidence that climate warming has influenced spring migration arrival dates of several species in Manitoba.

Tendances à Long-terme des Dates d'Arrivée Printanières des Oiseaux Migrateurs dans le Delta Marsh, Manitoba, en Relation avec les Changements Climatiques
Nest Building is an Indicator of Parental Quality in the Monogamous Neotropical Buff-Breasted Wren (Thryothorus Leucotis)
Authors: Gill Sharon A. , Stutchbury Bridget J. M.
Published: September 2019

In species with long-term partnerships, optimal mate preferences may differ from actual mate choice, and pair displays that advertise individual quality may be expected. We examined the relationship between nest-building and nestling-provisioning effort in Neotropical Buff-breasted Wrens (Thryothorus leucotis) to determine whether male or female expenditure during nest construction was used as an indicator of subsequent parental ability. Buff-breasted Wrens build two nest types: breeding nests used for raising offspring, and “dormitory“ nests built year-round and used by pairs for roosting overnight. The building effort of males was greater than that of their mates for dormitory nests, whereas male and female effort were similar during breeding-nest construction and nestling provisioning. Despite large within-sex variation in building and provisioning efforts, male and female effort within pairs were significantly positively correlated for construction of both nest types and for nestling feeding. Effort expended by males during dormitory-nest construction was positively correlated with nestling-provisioning effort, whereas female building effort was not. No relationship existed between effort in breeding-nest construction and nestling provisioning in either sex. These results suggest that effort in dormitory-nest construction was an indicator of male Buff- breasted Wren parental ability. Females that survived to the year following observation built dormitory nests at a lower rate than those that disappeared, which suggests that nest building may be costly and that by building more than females, males may increase the survival prospects of their partners. Dormitory-nest building by males may play dual roles throughout the year, indicating parental ability and investment in the partnership.

La Construcción de Nidos es un Indicador de la Calidad de los Padres en la Especie Neotropical Monógama Thryothorus leucotis
Effects of Food Abundance, Weather, and Female Condition on Reproduction in Tree Swallows (Tachycineta Bicolor)
Authors: Nooker Jacqueline K. , Dunn Peter O. , Whittingham Linda A.
Published: September 2019

Food abundance, weather, and female body condition are believed to influence the timing of breeding and reproductive performance of birds. We simultaneously studied the effects of weather and food abundance on reproduction in Tree Swallows (Tachycineta bicolor) while experimentally reducing female condition and foraging efficiency by clipping some flight feathers prior to egg laying. Control females laid larger clutches earlier in the season, had longer incubation periods, and raised heavier nestlings than experimental females. Fledging success did not differ after controlling for laying date and brood size. Greater insect abundance was associated with laying earlier in the season, heavier eggs, and shorter incubation periods. Most likely, feather-clipping affected clutch size through reduced foraging efficiency, which delayed the date of laying, rather than through loss of body condition. This outcome is consistent with the idea that Tree Swallows are “income” breeders that base their timing of reproduction on short-term rates of food intake near the time of breeding. Contrary to studies of other species, Tree Swallows do not appear to time their laying so that hatching will coincide with seasonal peaks in food supply. Rather, they appear to breed when temperature and food abundance are sufficient to allow females of a given body condition to initiate egg laying.

Efectos de la Abundancia de Alimento, del Clima y de la Condición de las Hembras sobre la Reproducción en Tachycineta bicolor
Diurnal Studies do not Predict Nocturnal Habitat Choice and Site Selection of European Golden-Plovers (Pluvialis Apricaria and Northern Lapwings (Vanellus Vanellus)
Authors: Gillings Simon , Fuller Robert J. , Sutherland William J.
Published: September 2019

Many species, including shorebirds, feed during both day and night, yet little is known about how this affects behavior and habitat preferences. European Golden-Plovers (Pluvialis apricaria) and Northern Lapwings (Vanellus vanellus) feeding on arable farmland were more widely dispersed at night: nocturnal flocks were smaller, typically monospecific, and occurred in many more fields than diurnal mixed-species flocks. Diurnal numbers of European Golden-Plovers could not be used to predict nocturnal numbers; this indicates that ranging behavior differed between day and night. For both species, nocturnal feeding was recorded on almost all nights, irrespective of moon phase. Northern Lapwing nocturnal feeding activity decreased with increasing cloud cover and decreasing ground temperature, but no clear relationships were detected between European Golden-Plovers’ nocturnal feeding activity and environmental variables. Habitat selection differed between day and night, and between species at night. Diurnal studies of habitat choice and site selection may misrepresent the full requirements of such species.

Los Estudios Diurnos no Predicen la Preferencia Nocturna de Hábitat ni la Selección Nocturna de Sitio en Pluvialis apricaria y Vanellus vanellus
Habitat and Sex Differences in Physiological Condition of Breeding Southwestern Willow Flycatchers (Empidonax Trailliiextimus)
Authors: Owen Jennifer C. , Sogge Mark K. , Kern Michael D.
Published: September 2019

The Southwestern Willow Flycatcher (Empidonax traillii extimus; here- after “flycatcher”) is a federally listed endangered species that breeds in densely vegetated riparian habitats dominated by native and exotic plants, including introduced monotypic saltcedar (Tamarix ramosissima). Some workers have theorized that saltcedar is unsuitable habitat for the flycatcher, primarily because it generally supports a smaller and less diverse invertebrate community (the flycatcher's food base) than native habitats (e.g. Salix spp.). However, differences in insect communities between native and saltcedar habitats are not proof that saltcedar habitats are inferior. The only way to evaluate whether the habitats differ in dietary or energetic quality is to document actual food limitation or its manifestations. Measurements of an individual's body condition and metabolic state can serve as indicators of environmental stressors, such as food limitation and environmental extremes. We captured 130 flycatchers breeding in native and saltcedar habitats in Arizona and New Mexico and measured 12 variables of physiological condition. These variables included body mass, fat level, body condition index, hematocrit, plasma triglycerides, plasma free fatty acids and glycerol, plasma glucose and beta-hydroxybutyrate, plasma uric acid, total leukocyte count, and heterophil-to-lymphocyte ratio. We found substantial sex-based differences in the condition of male and female flycatchers. Ten of the 12 measures of physiological condition differed significantly between the sexes. In all cases where male and female condition differed (except mass), the differences suggest that males were in poorer condition than females. We found few habitat-based differences in flycatcher condition. Only 3 of the 12 physiological condition indices differed significantly between habitats. Our data show that, at least in some parts of the flycatcher's range, there is no evidence that flycatchers breeding in saltcedar habitats exhibit poorer nutritional condition or are suffering negative physiological affects.

Diferencias entre Hábitats y Sexos en la Condición Fisiológica de Individuos Reproductivos en Empidonax traillii extimus