bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproductive Strategies of Northern Geese: Why Wait?
Authors: Ely Craig R. , Bollinger Karen S. , Densmore Roseann V. , Rothe Thomas C. , Petrula Michael J. , Takekawa John Y. , Orthmeyer Dennis L.
Published: September 2019

Migration and reproductive strategies in waterbirds are tightly linked, with timing of arrival and onset of nesting having important consequences for reproductive success. Whether migratory waterbirds are capital or income breeders is predicated by their spring migration schedule, how long they are on breeding areas before nesting, and how adapted they are to exploiting early spring foods at northern breeding areas. However, for most species, we know little about individual migration schedules, arrival times, and duration of residence on breeding areas before nesting. To document these relationships in a northern nesting goose, we radiotracked winter-marked Tule Greater White-fronted Geese (Anser albifrons elgasi; hereafter “Tule Geese”; n = 116) from the time of their arrival in Alaska through nesting. Tule Geese arrived on coastal feeding areas in mid-April and moved to nesting locations a week later. They initiated nests 15 days (range: 6–24 days) after arrival, a period roughly equivalent to the duration of rapid follicle growth. Tule Geese that arrived the earliest were more likely to nest than geese that arrived later; early arrivals also spent more time on the breeding grounds and nested earlier than geese that arrived later. The length of the prenesting period was comparable to that of other populations of this species, but longer than for goose species that initiate rapid follicle growth before arrival on the breeding grounds. We suggest that Tule Geese nesting in more temperate climates are more likely to delay breeding to exploit local food resources than Arctic-nesting species that may be constrained by short growing seasons.

Estrategias Reproductivas de los Gansos del Norte: ¿Por Qué Esperar?
Evolution of Coloniality in Birds: A Test of Hypotheses With the Red-Necked Grebe (Podiceps Grisegena)
Authors: Sachs Joel L. , Hughes Colin R. , Nuechterlein Gary L. , Buitron Deborah
Published: September 2019

Group breeding is perplexing, because individuals incur density-dependent fitness costs to breed in groups, yet no universal benefit appears to explain its evolution. Coloniality in birds, defined as dense nesting within limited territories, is a striking example of group breeding. Adaptive explanations for coloniality are diverse, and several research approaches have emerged. Here, we test models for the evolution of coloniality with a population of Red-necked Grebes (Podiceps grisegena). We distinguish habitat models from conspecific models for explaining the adaptive evolution of coloniality. Habitat models propose that the fitness benefits of colonial breeding are gained through the characteristics or location of the colony site, whereas conspecific models posit that the benefits of colonial breeding are gained solely from nesting near conspecifics. Red-necked Grebes are waterbirds that typically nest in a dispersed fashion, only rarely nesting in colonies. Both dispersed and colonial nesting co-occurred in the study population, and aquatic nests were found in three distinct habitat types. We gathered detailed demographic data and used analyses of covariance to test whether variation in habitat type or conspecific aggregation best explained differences in breeding success across the population. We further used fitness, genetic, and spatial data to test whether kin selection, sexual selection, or conspecific reproductive-success cueing may drive colony formation. The data provided strong support for a habitat-based model and inconsistently supported conspecific models. Our results suggest that colonial individuals of this population gain selfish benefits from relatively rare, high-quality habitat rather than from proximity of conspecifics.

Evolución de la Colonialidad en las Aves: Una Evaluación de las Hipótesis en Podiceps grisegena
Seasonal Egg-Mass Variation and Laying Sequence in a Bird With Facultative Brood Reduction
Authors: D'Alba Liliana , Torres Roxana
Published: September 2019

Females may maximize their lifetime reproductive output by adjusting their investment in each breeding event to the perceived likelihood of success. The Blue-footed Booby (Sula nebouxii) is a long-lived seabird with facultative siblicide. We examined whether there is differential resource allocation to eggs with laying order and whether greater egg mass increases hatching probability, chick survival, hatching interval, and mass and size at hatching. We found that the relative investment in first and second eggs decreased as the season advanced: second eggs were slightly (1.5%) heavier than first eggs in early clutches; by contrast, first eggs were 2% heavier than second eggs in late clutches. Accordingly, hatching probability increased with laying date for first eggs and decreased for second eggs. The mass of the egg increased hatching probability, and no effect on chick survival was detected. Laying interval increased after a heavier egg was laid, and heavier eggs produced heavier hatchlings. Hatching intervals were positively related to laying intervals, but egg mass was unrelated to the length of the incubation period and the hatching interval. Our results suggest that egg mass influences embryo survival and that Blue-footed Booby females may adaptively allocate resources to eggs of different laying order according to breeding conditions.

Variación del Peso de los Huevos y Secuencia de Postura en un Ave con Reducción Facultativa de la Nidada
Time-of-Detection Method for Estimating Abundance From Point-Count Surveys
Authors: Alldredge Mathew W. , Pollock Kenneth H. , Simons Theodore R. , Collazo Jaime A. , Shriner Susan A.
Published: September 2019

Point-count surveys are often used to collect data on the abundance and distribution of birds, generally as an index of relative abundance. Valid comparison of these indices assumes that the detection process is comparable over space and time. These restrictive assumptions can be eliminated by estimating detection probabilities directly. We generalize a recently proposed removal model for estimating detection probabilities using a time-of-detection approach, which can account for more sources of variation in point-count data. This method is specifically designed to account for variation in detection probabilities associated with singing rates of birds. Our model accounts for both availability bias and detection bias by modeling the combined probability that a bird sings during the count, and the probability that it is detected given that it sings. The model requires dividing the count into several intervals and recording detections of individual birds in each interval. We develop maximum-likelihood estimators for this approach and provide a full suite of models based on capture-recapture models, including covariate models. We present two examples of this method: one for four species of songbirds surveyed in Great Smoky Mountains National Park using three unequal intervals, and one for the Pearly-eyed Thrasher (Margarops fuscatus) surveyed in Puerto Rico using four equal intervals. Models incorporating individual heterogeneity were selected for all data sets using information-theoretic model-selection techniques. Detection probabilities varied among count-time intervals, which suggests that birds may be responding to observers. We recommend applying this method to surveys with four or more equal intervals to reduce assumptions and to take full advantage of standard capture-recapture software. The time-of-detection approach provides a better understanding of the detection process, especially when singing rates of individual birds affect detection probabilities.

Estimación de la Abundancia en Puntos de Conteo Mediante el Método del Tiempo de Detección
Diurnal and Nocturnal Roost Site Fidelity of Dunlin (Calidris Alpina Pacifica) at Humboldt Bay, California
Authors: Conklin Jesse R. , Colwell Mark A.
Published: September 2019

Shorebird roosts are often considered traditional, on the basis of predictable occupancy by large numbers of birds over long periods. However, fidelity of individuals to roosts at fine spatial and temporal scales, particularly at night, has rarely been described. We compared diurnal and nocturnal use of high-tide roosts by radiotagged Dunlin (Calidris alpina pacifica) wintering (November-March) at Humboldt Bay, California. Despite high fidelity to the study area, fidelity to particular roosts was relatively low and highly variable. At night, Dunlin used fewer roosts, were more faithful to primary roosts, and moved shorter distances between successive roosts than during the day. Day and night roosts differed in location, habitat, and distance from tidal flats. At night, Dunlin made greater use of pasture, and less use of islands and manmade structures. Day and night strategies of high-tide space use by Dunlin may be related to differences in food availability or predation danger. Our results illustrate that notions of tradition and site fidelity are scale-dependent and that knowledge of space use across the full range of environmental conditions is necessary for appropriate management of shorebird habitat.

Fidelidad a los Sitios de Descanso Diurnos y Nocturnos en Calidris alpina pacifica en la Bahía de Humboldt, California
High Connectivity and Minimal Genetic Structure Among North American Boreal Owl (Aegolius Funereus) Populations, Regardless of Habitat Matrix
Authors: Koopman Marni E. , Hayward Gregory D. , McDonald David B.
Published: September 2019

Habitat connectivity and corridors are often assumed to be critical for the persistence of patchily distributed populations, but empirical evidence for this assumption is scarce. We assessed the importance of connectivity among habitat patches for dispersal by a mature-forest obligate, the Boreal Owl (Aegolius funereus). Boreal Owls demonstrated a lack of genetic structure (θ = 0.004 ± 0.002 [SE]) among subpopulations, regardless of matrix type and extent, which indicates that unforested matrix does not act as a barrier to dispersal for this vagile species. We found only slightly higher genetic distances (Cavalli-Sforza chord distances ranged from 0.015 to 0.025) among patchily distributed Rocky Mountain subpopulations as compared with largely contiguous boreal-forest subpopulations (0.013 to 0.019) and no evidence of a genetic split across the expansive high plains of Wyoming. Even the most isolated subalpine patches are connected via gene flow. As northern boreal forests continue to experience intensive harvest of mature stands, geographic dispersion of Boreal Owl habitat may begin to more closely resemble that found in the Rocky Mountains. We suggest that decreased connectivity poses much less of a threat to continued abundance of this mature-forest obligate than overall loss of nesting and foraging habitat. Assessment of the importance of corridors and connectivity should be conducted on a species-by-species basis, given the variation in response of species to discontinuity of habitat, even among closely related taxa or guilds.

Alta Conectividad y Estructura Genética Mínima entre Poblaciones Norteamericanas de Aegolius funereus, Independientemente de la Matriz del Hábitat
Algemene en Schaarse Vogels van Nederland [Common and Scarce Birds of The Netherlands]
Authors: van der Linde Kim
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.
Goudplevieren en Wilsterflappers: Eeuwenoude Fascinatie voor Trekvogels [Golden Plovers and Wilsternetters: A Century-old Fascination for Migratory Birds]
Authors: van der Linde Kim
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.
Variation in the Wing Morphology of Western Sandpipers (Calidris Mauri) in Relation to Sex, Age Class, and Annual Cycle
Authors: Fernández Guillermo , Lank David B.
Published: September 2019

We analyzed differences in wing morphology between sexes and among age classes of Western Sandpipers (Calidris mauri) to assess possible relationships with differential migration, acrobatic aerial displays, and potential vulnerability to predation, using size-constrained component analysis. Data on wing morphology of all four sex and age classes were available from birds spending the nonbreeding season in northwestern Mexico, and data on females were available from throughout the annual cycle. During the nonbreeding season, females had longer and more pointed wings than males. Within each sex, adults had longer and more pointed wings than immature birds. Throughout the annual cycle, adult females tended to have longer and more pointed wings than immature females. The longer and more pointed wings of females are consistent with selection on flight efficiency for longer migration distances. The shorter and rounder wings of males are consistent with stronger selection for agility in flight during acrobatic aerial displays, but also with weaker selection for flight efficiency because of shorter migration distances. The rounder wings of immature birds are most consistent with stronger selection for take-off performance as an antipredator adaptation, at a cost of lower flight efficiency during long-distance migratory flight. Considering intraspecific sex and age class differences in wing morphology of species with differential migration complements interspecific comparisons assessing the relative importance of selective agents acting on this character.

Variación en la Morfología del ala de Calidris mauri con Relación al Sexo, la Edad y el Ciclo Anual
A Test of Cues Affecting Habitat Selection by Wading Birds
Authors: Gawlik Dale E. , Crozier Gaea E.
Published: September 2019

We examined foraging-habitat selection by free-ranging wading birds presented with different social and environmental cues by conducting two experiments in eight replicate ponds adjacent to the northern border of the Florida Everglades. The first experiment examined the relative influence of a social (presence of a flock of decoys) and environmental (water depth) cue on the selection of ponds. The second experiment examined the influence of two environmental cues (water depth and fluctuating water level) on the selection of ponds. In the first experiment, wading birds were most attracted to ponds with both the presence of a flock of decoys and shallow water. The social and environmental cues both had the same attractive potential to wading birds. In the second experiment, birds were again attracted to ponds with shallow water; however, fluctuating water level had no significant influence on foraging-habitat selection. If birds do not perceive fluctuating water levels as a cue to habitat quality, then the well-documented relationship between nesting success and fluctuating water levels likely stems from birds responding to factors that covary with water-level changes.

Una Prueba de las Señales que Afectan la Selección de Hábitat por Aves Vadeadoras
Bird Coloration.
Authors: Brush Alan H.
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.
Roberts Birds of Southern Africa, 7th ed
Authors: Urban Emil K.
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.
The Antitrochanter of Birds: Form and Function in Balance
Authors: Hertel Fritz , Campbell Kenneth E.
Published: September 2019

The antitrochanter is a uniquely avian osteological feature of the pelvis that is located lateral to the postero-dorsal rim of the acetabulum. This feature makes the avian hip joint unique among all vertebrates, living and fossil, in that a significant portion of the femoral-pelvic articulation is located outside of the acetabulum. This additional acetabular articulation occurs between the neck of the femur and the antitrochanter, and operates as a hinge joint or ginglymus. It is complementary to the articulation of the head of the femur with the acetabulum, which is a pivot joint or trochoides. The size, location, and spatial orientation of the antitrochanter were determined for 77 species of birds representing a variety of hindlimb functions (e.g., highly cursorial, vertical clinging, foot-propelled diving) and spanning a wide range of body sizes (swifts to rheas). The area of the antitrochanter is a good predictor of body mass in birds; its position and orientation are reasonably consistent within hindlimb morphofunctional groups, but not among all birds. The antitrochanter serves as a brace to prevent abduction of the hindlimb and to absorb stresses that would otherwise be placed on the head of the femur during bipedal locomotion. The drum-in-trough-like form of the antitrochanter-femur articulation tends to assist in the transfer of long-axis rotational movements of the femur to the pelvis. The avian antitrochanter is a derived feature of birds that evolved as an aid in maintaining balance during bipedal terrestrial locomotion.

El Antitrocánter en las Aves: Forma y Función en el Equilibrio
Rates Versus Counts: Fall Molts of Lucy's Warblers (Vermivora Luciae)
Authors: Rohwer Sievert , Navarro Adolfo G. , Voelker Gary
Published: September 2019

New specimens from Sinaloa, Mexico, as well as two older specimens, show that both adult and recently fledged Lucy's Warblers (Vermivora luciae) often move far south of their breeding grounds to molt in the tropical deciduous forests of northwestern Mexico. Remarkably, the first preformative (= first prebasic) molt is complete in Lucy's Warblers, including the replacement of flight feathers, primary coverts, and rectrices; thus, previous aging criteria based on the wear and appearance of these feathers are invalid. We suggest that the recent conclusion that Lucy's Warblers molt on their breeding grounds (Voelker and McFarland 2002) is an artifact of more collecting in the southwestern United States than in western Mexico during late summer. An index of relative collecting in Mexico and the United States, as well as data from constant-effort mist netting, suggest that most Lucy's Warblers move south to molt.

Tasas versus Conteos: Mudas de Otoño de Vermivora luciae
Mark-Recapture-Recovery Modeling and Age-Related Survival in Little Penguins (Eudyptula Minor)
Authors: Sidhu Leesa A. , Catchpole Edward A. , Dann Peter
Published: September 2019

We analyzed yearly mark-recapture-recovery information collected over a 36-year period for the Little Penguins (Eudyptula minor) of Phillip Island in southeastern Australia. We show that it is feasible to model age-dependence for the survival, recapture, and recovery probabilities simultaneously, and that such a modeling scheme yields biologically realistic age structures for the model parameters. We provide illustrations of potentially erroneous results that may arise when researchers fail (1) to consider simultaneous age-dependence or (2) to detect annual variations that may mask age-dependence. From 1968 to 2004, 23,686 chicks were flipper-banded; 2,979 birds were encountered after fledging, and 1,347 were ultimately recovered dead. We found low survival of 17% in the first year of life, increasing to 71% in the second year of life, 78% in the third year, and 83% thereafter, and declining gradually after nine years of age. A population model allowing for immigration of birds from areas surrounding the study sites fits the observed stable population in the study sites.

Modelado de Marca-Recaptura-Recuperación y Supervivencia Relacionada con la Edad en Eudyptula minor
Effects of Size and Migratory Behavior on the Evolution of Wing Molt in Terns (Sternae): A Phylogenetic-Comparative Study
Authors: Bridge Eli S. , Voelker Gary , Thompson Christopher W. , Jones Andrew W. , Baker Allan J.
Published: September 2019

Approximately 60% of the 45 species of terns (Sternae) have an unusual form of wing molt in which a variable number of inner primaries and outer secondaries are replaced two or three times in a single year—a process that has been called “repeated molt.” Although several hypotheses have been proposed for the maintenance of repeated molt, few data exist regarding potential selective forces that may have favored the evolution of this molt strategy, and there are no explanations for the high degree of interspecific variation in the extent of repeated molt. Preliminary investigations indicated that large terns tended to have less repeated molt than small terns and that the presence of repeated molt appeared to be associated with migratory behavior. We examined these initial findings by combining data from the literature, from examinations of museum specimens, and from a recent molecular phylogeny of the terns to perform phylogenetic-comparative tests. First, we used independent contrasts to verify that the association between large terns and less repeated molt was significant and not a result of shared ancestry. Second, we used tests for binary character association to evaluate the apparent link between repeated molt and migratory behavior. The results of these tests, along with reconstructions of ancestral states, led to a potential explanation for the origin of repeated molt, in which a tropical, sedentary ancestor gave rise to several lineages that spread to temperate areas and adopted a migratory life history. With this shift to a more seasonal regime came shortened breeding periods and perhaps more time for molt, which could have led to modifications of the ancestral molting strategy and the origin of repeated molt.

Efectos del Tamaño y del Comportamiento Migratorio en la Evolución de la Muda del Ala en los Gaviotines (Sternae): Un Estudio Filogenético Comparativo
Historical Biogeography of the New World Solitaires (Myadestes SPP)
Authors: Miller Matthew J. , Bermingham Eldredge , Ricklefs Robert E.
Published: September 2019

Solitaires (Myadestes spp.) are montane-forest birds that are widely distributed throughout the New World, ranging from Alaska to northern Bolivia and including both Hawaii and the West Indies. To understand the origins of this impressive distribution, we used five mitochondrial gene sequences to reconstruct the historical biogeography of the genus. The resulting phylogeny indicates a rapid initial spread of the genus to occupy most of its contemporary continental range at least as far south as lower Mesoamerica, plus Hawaii and the Greater Antilles. The North American M. townsendi appears to be the sister taxon of the rest of Myadestes. Myadestes obscurus of Hawaii is more closely allied to Mesoamerican lineages than to M. townsendi. The strongly supported sister relationship of the two West Indian taxa, M. elisabeth and M. genibarbis, indicates a single colonization of the West Indies. A more recent node links the Andean M. ralloides to the Mesoamerican M. melanops and M. coloratus. A standard molecular clock calibration of 2% sequence divergence per million years for avian mitochondrial DNA suggests that the initial diversification of Myadestes occurred near the end of the Miocene (between 5 and 7.5 mya). Cooler temperatures and lower sea levels at that time would have increased the extent of montane forests and reduced overwater dispersal distances, possibly favoring range expansion and colonization of the West Indies. The split between South American and southern Mesoamerican lineages dates to ∼3 mya, which suggests that Myadestes expanded its range to South America soon after the Pliocene rise of the Isthmus of Panama. Despite the demonstrated capacity of Myadestes for long-distance dispersal, several species of Myadestes are highly differentiated geographically. Phylogeographic structure was greatest in the West Indian M. genibarbis, which occurs on several islands in the Greater Antilles and Lesser Antilles, and in the Andean M. ralloides. The phylogeographic differentiation within M. ralloides was not anticipated by previous taxonomic treatments and provides a further example of the importance of the Andes in the diversification of Neotropical birds. Overall, the historical biogeography of Myadestes suggests that range expansion and long-distance dispersal are transient population phases followed by persistent phases of population differentiation and limited dispersal.

Biogeografía Histórica de los Zorzales del Género Myadestes
Metabolic Routing of Dietary Nutrients in Birds: Effects of Dietary Lipid Concentration on δ13C of Depot Fat and Its Ecological Implications
Authors: Podlesak David W. , McWilliams Scott R.
Published: September 2019

During migration, many songbirds eat primarily fruit while depositing fat. Given that some fruits contain mostly carbohydrate and others contain mostly lipid, the ability of birds to fatten may depend on the macronutrient composition of the fruit. Stable isotopes of carbon may be useful in determining the source of nutrients used for synthesizing fat, because the enzyme that regulates the transfer of carbon skeletons from carbohydrate into fat synthesis has a higher affinity for 12C than for 13C, whereas dietary lipids can be directly incorporated into animal fat. Thus, fat stores of animals that are synthesized directly from dietary lipid should have isotopic signatures similar to dietary lipid, whereas biosynthesis of fats from dietary carbohydrates should produce changes in isotopic signatures. We tested these predictions by manipulating the concentrations and isotopic signatures of macronutrients in diets fed to Yellow-rumped Warblers (Dendroica coronata). The δ13C of depot fat in birds fed high-lipid diets was similar to that of dietary lipid, whereas δ13C of depot fat in birds fed low-lipid diets indicated that a combination of dietary lipid and carbohydrate were used to synthesize depot fat. Models that incorporated 8% discrimination between dietary carbohydrate and depot fat consistently estimated the proportion of dietary lipid and carbohydrate routed into depot fat. Stable-isotope analysis of macronutrients in the diet of wild birds combined with estimates of the effects of diet composition on the isotopic signature of depot fat in birds offer a method to identify the relative importance of nutritional resources used by songbirds to deposit fat.

Rutas Metabólicas de Nutrientes Dietarios en Aves: Efectos de la Concentración de Lípidos Dietarios sobre δ13C en los Depósitos de Grasa y sus Implicancias Ecológicas
Phenology of Tropical Birds in Peninsular Malaysia: Effects of Selective Logging and Food Resources
Authors: Yap Charlotte A-M. , Sodhi Navjot S. , Peh Kelvin S-H.
Published: September 2019

The increasing prevalence of selective logging in Southeast Asian tropical rainforests compels much-needed studies to examine its effects on the vital life-cycle events of their resident understory birds, which are particularly sensitive to such degradation. Food abundance, which can be an important factor in avian phenology, may be affected by selective logging. Therefore, studies that compare food abundance and breeding and molting occurrence simultaneously at the same sites are important for the ecological monitoring of such logging regimes. Using bimonthly mist netting in two rainforest areas in Peninsular Malaysia, we assessed the breeding and molting occurrence and diets of understory birds and compared the abundance of food resources in unlogged forests and forests that had been selectively logged 30 years before. Our study revealed no differences between forest types in overall understory-resident bird abundance; comparative species richness; feeding-guild composition; breeding and molting occurrence and temporal variation; or arthropod, fruit, and flower abundance. The similarity in food resources could account for the similarity in avian phenological characteristics between forest types. Increased breeding corresponded with increased food abundance at the feeding-guild level, and dietary data supported these findings. Breeding cycles of sensitive indicator groups such as understory resident birds are likely to depend on food abundance and forest structure and, thus, on selective logging. Our observation of undiminished avian breeding and molting occurrence in selectively logged forests is an encouraging indication of their conservation potential. However, we emphasize that differences in selective logging practices could affect the forest structure and avifauna differently. Setting thresholds for extraction and regeneration time and subscribing to minimum-impact methods that reduce collateral damage are essential if selectively logged areas are to maintain most of their initial biodiversity.

Fenología de Aves Tropicales en Malasia Peninsular: Efectos de la Tala Selectiva y los Recursos Alimenticios
Genetic Identification of Eggs Purportedly From the Extinct Labrador Duck (Camptorhynchus Labradorius)
Authors: Chilton Glen , Sorenson Michael D.
Published: September 2019

Material extracted from inside the shells of nine purported Labrador Duck (Camptorhynchus labradorius) eggs was subjected to DNA extraction and polymerase chain reaction (PCR) amplification. For each egg, partial sequences of one to three mitochondrial genes (12S, ND2, and control region) were compared with sequences derived from a Labrador Duck specimen and representatives of several other waterfowl species. Sequences from six eggs were consistent with those of the Red-breasted Merganser (Mergus serrator), whereas the sequences from one egg was most consistent with that of the Common Eider (Somateria mollissima). The remaining two eggs yielded sequences consistent with that of the Mallard (Anas platyrhynchos) or a domestic duck. Regrettably, none of the eggs provided additional information about the breeding grounds of the extinct Labrador Duck. To our knowledge, this is the first report of DNA extraction and amplification from old eggshells of birds.

Identification génétique d'œufs présumés provenir de l'espèce disparue Camptorhynchus labradorius
Distinctiveness, Use, and Value of Midwestern Oak Savannas and Woodlands as Avian Habitats
Authors: Grundel Ralph , Pavlovic Noel B.
Published: September 2019

Oak savannas and woodlands historically covered millions of hectares in the midwestern United States but are rare today. We evaluated the ecological distinctiveness and conservation value of savannas and woodlands by examining bird distributions across a fire-maintained woody-vegetation gradient in northwest Indiana encompassing five habitats—open habitats with low canopy cover, savannas, woodlands, scrublands, and forests—during migration, breeding, and overwintering. Savannas and woodlands were significantly different in overall bird species composition from open and forest habitats but were often intermediate between open and forest in guild densities. Few bird species were consistently and highly concentrated in savannas or woodlands, and the Red-headed Woodpecker (Melanerpes erythrocephalus) was the only species significantly more abundant in savannas and woodlands than in open, scrub, and forest habitats. Fire frequency over a 15-year interval was a significant predictor of bird community composition and was positively related to species diversity, spring transient migrant density, and density of the most threatened species. Each habitat type had characteristics potentially important for avian conservation. Scrub had the highest density of transient migrants, which suggests it plays an important role as migration stopover habitat. More species were significantly concentrated in open or forest habitats than in the other habitats. Lack of species concentration and intermediate community composition suggested that birds experienced savannas and woodlands more as ecotones than as habitats distinct from forests or grasslands. However, this intermediate character can benefit conservation, as evidenced by savannas and woodlands having the highest density of the most threatened species along this woody-vegetation gradient.

Características Únicas, Uso y Valor de las Sabanas y Bosques Abiertos de Roble del Oeste Central como Hábitats para las Aves
Experimental Analysis of The Auditory Detection Process on Avian Point Counts
Authors: Simons Theodore R. , Alldredge Mathew W. , Pollock Kenneth H. , Wettroth John M.
Published: September 2019

We have developed a system for simulating the conditions of avian surveys in which birds are identified by sound. The system uses a laptop computer to control a set of amplified MP3 players placed at known locations around a survey point. The system can realistically simulate a known population of songbirds under a range of factors that affect detection probabilities. The goals of our research are to describe the sources and range of variability affecting point-count estimates and to find applications of sampling theory and methodologies that produce practical improvements in the quality of bird-census data. Initial experiments in an open field showed that, on average, observers tend to undercount birds on unlimited-radius counts, though the proportion of birds counted by individual observers ranged from 81% to 132% of the actual total. In contrast to the unlimited-radius counts, when data were truncated at a 50-m radius around the point, observers overestimated the total population by 17% to 122%. Results also illustrate how detection distances decline and identification errors increase with increasing levels of ambient noise. Overall, the proportion of birds heard by observers decreased by 28 ± 4.7% under breezy conditions, 41 ± 5.2% with the presence of additional background birds, and 42 ± 3.4% with the addition of 10 dB of white noise. These findings illustrate some of the inherent difficulties in interpreting avian abundance estimates based on auditory detections, and why estimates that do not account for variations in detection probability will not withstand critical scrutiny.

Análisis Experimentales del Proceso de Detección Auditiva en Puntos de Conteo de Aves
Breeding Habitat Requirements and Selection by Olrog's Gull (Larus Atlanticus), A Threatened Species
Authors: Borboroglu Pablo García , Yorio Pablo
Published: September 2019

We studied habitat requirements and selection of Olrog's Gulls (Larus atlanticus) breeding at six colonies along 2,500 km of coastline in central Argentina that encompasses its entire distributional range. Colonies were located only on islands that ranged in size between 0.4 and 125.8 ha, and the islands' distance to the mainland varied from 0.12 to 16.7 km. Colonies ranged in size between 12 and 341 nests. In three of the colonies, gulls nested in subcolonies (range: 8–239 nests). They nested at relatively high densities, with a mean inter-nest distance of 0.66 ± 0.25 m. Logistic regression analysis to compare nest and random-site characteristics at each colony showed that Olrog's Gulls selected sites that were close to the high-tide line, at a lower height above sea level, far from available vegetation, and had lower vegetation cover over the nest. Olrog's Gulls showed a significant positive association with Kelp Gulls (L. dominicanus), an expanding generalist species that also nests in similar habitats. Current trends in coastal development, particularly in the Olrog's Gulls' main breeding grounds of southern Buenos Aires, indicate the urgent need for habitat-protection guidelines for this threatened species. Moreover, its breeding association with Kelp Gulls suggests a potential spatial conflict and highlights the need for increased monitoring and management actions.

Selección y Requerimientos de Hábitat Reproductivo en Larus atlanticus, una Especie Amenazada
Small-Prey Profitability: Field Analysis of Shorebirds’ use of Surface Tension of Water to Transport Prey
Authors: Estrella Sora M. , Masero José A. , Pérez-Hurtado Alejandro
Published: September 2019

Previous laboratory studies have shown that Red-necked Phalarope (Phalaropus lobatus), Wilson’s Phalarope (P. tricolor), Western Sandpiper (Calidris mauri), and Least Sandpiper (C. minutilla) use the surface tension of water surrounding a prey item to transport it from bill tip to mouth. Although such experimental work suggests that many species of shorebird may be capable of surface-tension feeding, no field studies have been done that examine this possibility. We studied the occurrence and interspecific variation in the performance of surface-tension transport (STT) in wild shorebirds feeding on identical prey items in shallow water. All shorebirds videotaped—Little Stint (C. minuta), Dunlin (C. alpina), Sanderling (C. alba), Curlew Sandpiper (C. ferruginea), Common Redshank (Tringa totanus), and Black-winged Stilt (Himantopus himantopus)—used STT to feed on small prey items. Individuals employing STT used one or several cycles of jaw spreading to transport the prey contained in a drop of water upward along the bill cavity, an action indicative of STT. Two distinct types of prey transport were observed: (1) use of STT in isolation by calidridine species following the description given in previous studies (i.e., an absence of other feeding mechanisms such as tongue movements, suction, or inertial transport), and (2) STT aided by inertial transport (head jerks) as seen in Common Redshank and Black-winged Stilt. Measured prey-transport variables (number of cycles, total time, and speed of transport) varied among species. The absence of significant relationships between these variables and measures of external morphology (bill length, bill length-to-width ratio, and bill length-to-depth ratio) suggests that some interspecific variations in STT performance may be attributable to differences in internal bill morphology. We show that STT is a common feeding mechanism in small or medium- sized shorebird species that feed on small prey items in shallow water. Birds using STT transported ≤3.6× faster than the theoretical value predicted by a previous model and can achieve high intake rates when foraging on high densities of available small prey items.

Ventajas de las Presas Pequeñas: Análisis de Campo del Uso de la Tensión Superficial del Agua por las Aves Playeras para Transportar las Presas
Malaria Prevalence and White-Blood-Cell Response to Infection in a Tropical and in a Temperate Thrush
Authors: Ricklefs Robert E. , Sheldon Kimberly S.
Published: September 2019

To evaluate the possibilities and limitations of using white-blood-cell (WBC) counts to characterize investment in immune-system function, we compared the prevalence and intensity of malaria infections and concentrations of WBCs in the American Robin (Turdus migratorius) in Michigan and Missouri and in the Clay- colored Robin (T. grayi) in central Panama. We ascertained infection by polymerase chain reaction (PCR) screening and quantified infection intensity and WBC concentrations by visual inspection of blood smears. Because few parasites were observed on smears, we assumed that most cases of malaria represented chronic, rather than acute, infections. Prevalence of haemosporidian infection (Panama 41%, Missouri 57%, Michigan 63%) did not differ significantly between locations. However, most infections in Panama were undetected on blood smears, whereas more than half were apparent on smears in Michigan and Missouri. Among WBCs, lymphocytes were the most abundant type, followed by heterophils; eosinophils and lymphocytes were more common in the North American sample than in Panama, and their numbers in Michigan were significantly higher in infected than in noninfected individuals. Tropical T. grayi apparently maintained infections at lower intensities but appeared to accomplish this in spite of lower abundances of immune-system cells. Furthermore, analyses of blood smears of Turdus spp. from elsewhere in the tropics revealed a wide range of prevalence, which suggests that either the regional presence of haemosporidians or the ability of hosts to control infections cannot be learned from limited samples. Additional species surveyed in Michigan and Panama revealed no consistent pattern in either infection intensity or WBC concentrations. Infection and response appear to be highly idiosyncratic. In agreement with other authors, we caution that blood parameters are difficult both to interpret and to sam- ple adequately in tests of regional or other effects.

Prevalencia de Malaria y Respuesta de Glóbulos Blancos a la Infección en un Zorzal de la Zona Tropical y Uno de la Zona Templada
Nesting Success of Acadian Flycatchers (Empidonax Virescens) in Floodplain Forest Corridors
Authors: Chapa-Vargas Leonardo , Robinson Scott K.
Published: September 2019

Reconnecting forest patches, including those of floodplain forest, often involves the creation of long, narrow corridors that have the potential to act as ecological traps for wildlife. We examined the effect of forest width and habitat composition of the landscapes immediately around nest patches on survival and parasitism of 359 Acadian Flycatcher (Empidonax virescens) nests in the Cache River Bioreserve in southern Illinois. Nests were distributed among 19 floodplain forest corridors along a small river system that is being restored and reconnected along its original floodplain. The corridors spanned a range of widths (80–3,170 m) and varied with the presence or absence of natural water-related habitats (beaver ponds, backwater swamps, and creeks). Although nest success varied slightly between stages of the breeding cycle, confidence intervals overlapped, which suggests constant nest success throughout the breeding cycle. Nest survival was relatively high by regional standards but did not vary significantly with any of the landscape variables measured. Contrary to predictions, probabilities of brood parasitism decreased with increasing proportions of anthropogenic habitats surrounding nests. Probabilities of brood parasitism also decreased, but only slightly, as the breeding season progressed. Finally, Acadian Flycatcher nests were located significantly more often near natural (forest-water interface) edges than expected at random. Narrow corridors such as those along floodplain restoration projects do not necessarily create ecological traps for all forest species. Acadian Flycathcers, however, are one of the only forest-nesting Neotropical migrants that nest in narrow corridors and, therefore, may be less vulnerable to negative effects of fragmentation.

Éxito de Nidificación de Empidonax virescens en Corredores de Bosque de Planicies Inundables
Survival and Breeding Advantages of Larger Black Brant (Branta Bernicla Nigricans) Goslings: Within- and Among-Cohort Variation
Authors: Sedinger James S. , Chelgren Nathan D.
Published: September 2019

We examined the relationship between mass late in the first summer and survival and return to the natal breeding colony for 12 cohorts (1986-1997) of female Black Brant (Branta bernicla nigricans). We used Cormack-Jolly-Seber methods and the program MARK to analyze capture-recapture data. Models included two kinds of residuals from regressions of mass on days after peak of hatch when goslings were measured; one based on the entire sample (12 cohorts) and the other based only on individuals in the same cohort. Some models contained date of peak of hatch (a group covariate related to lateness of nesting in that year) and mean cohort residual mass. Finally, models allowed survival to vary among cohorts. The best model of encounter probability included an effect of residual mass on encounter probability and allowed encounter probability to vary among age classes and across years. All competitive models contained an effect of one of the estimates of residual mass; relatively larger goslings survived their first year at higher rates. Goslings in cohorts from later years in the analysis tended to have lower first-year survival, after controlling for residual mass, which reflected the generally smaller mean masses for these cohorts but was potentially also a result of population-density effects additional to those on growth. Variation among cohorts in mean mass accounted for 56% of variation among cohorts in first-year survival. Encounter probabilities, which were correlated with breeding probability, increased with relative mass, which suggests that larger goslings not only survived at higher rates but also bred at higher rates. Although our findings support the well-established linkage between gosling mass and fitness, they suggest that additional environmental factors also influence first-year survival.

Supervivencia y Ventajas Reproductivas de los Pichones de Mayor Tamaño de Branta bernicla nigricans: Variación entre y dentro de las Cohortes
Modeling Population Growth of The Ovenbird (Seiurus Aurocapilla) in the Southern Appalachians
Authors: Podolsky Andrei L. , Simons Theodore R. , Collazo Jaime A.
Published: September 2019

Studies of source-sink dynamics are often prompted by concerns about negative population trends. Estimates of population trajectories are usually based on assumptions about survival rates and empirical measures of fecundity. Most models ignore the influence of the rates of renesting and multiple brooding. We used the Ovenbird (Seiurus aurocapilla) as a model Neotropical migratory songbird species to investigate the relative effects of annual female survival and components of annual fecundity on population growth rates. We applied productivity data from a three- year field study and data from Hann (1937) to several models of annual fecundity to examine the sensitivity of lambda to variations in annual female survival and the likelihood of renesting and double-brooding. Our simulations illustrate the importance of incorporating estimates of annual survival and rates of additional breeding attempts in songbird population models because population growth rates are quite sensitive to variations in these parameters. Lambda is especially sensitive to survival estimates and changes with them at the same order of magnitude. Whenever feasible, female survival and probabilities of additional breeding attempts should be estimated by direct methods. The indirect methods used in our study (annual female survival estimated from the age ratio of breeding females, and rates of renesting and double- brooding determined from the timing of reproduction) probably underestimated these parameters.

Modelado del Crecimiento Poblacional de Seiurus aurocapilla en el Sur de los Apalaches