bluuebunny/crossref_metadata_2025_split huggingface dataset:
Responses of Male Tropical Mockingbirds (Mimus Gilvus) to Variation in Within-Song and Between-Song Versatility
Authors: Botero Carlos A. , Vehrencamp Sandra L. 
Published: September 2019

AbstractDespite their large vocal repertoires and otherwise highly versatile singing style, male mockingbirds (Mimus spp.) sometimes sing in a highly repetitive fashion. We conducted a playback experiment to determine the possible signal value of different syllable-presentation patterns during simulated male intrusions in the Tropical Mockingbird (Mimus gilvus), testing the hypothesis that more repetitive singing represents a stronger threat and generates a stronger aggressive response. Responses were measured in terms of approach and singing behavior and were analyzed using McGregor’s (1992) multivariate method. We also introduce the use of survival analysis for analyzing response variables for which subjects do not perform the behavior in question in at least one of the replicates (known as “right-censored variables” in the statistical literature). As predicted by theory, experimental subjects responded more aggressively to songs composed of a single note than to variable ones. However, versatility at the between-song level had an opposite effect: high song-switching rates generated stronger responses than low ones. Given the lack of a statistical interaction between within-song versatility and switching rate, we conclude that these two parameters may serve independent purposes and possibly transmit different information. We discuss the possibility that the signal value of variation in vocal versatility lies in the mediation of territorial conflicts, the attraction of female partners, the mediation of conflicts over access to reproductive females, or some combination of these functions.Respuestas de Machos de Mimus gilvus a Variación en Versatilidad Vocal Dentro- y Entre-cantos
Arthropod Resource Partitioning Among Omnivorous Tanagers (Tangara SPP.) in Western Ecuador
Authors: Naoki Kazuya 
Published: September 2019

AbstractThe distribution and abundance of food are primary factors affecting resource-use patterns in birds. Many bird species eat several food types, which may differ in their distribution and overall abundance. I studied foraging ecology of seven sympatric species of Tangara at Mindo, Ecuador, to determine whether the patterns of resource use differed between two food types: arthropods and fruits. Interspecific differences in arthropod-foraging were manifested in the fine segregation of microhabitat preference combined with different habitat use. By contrast, interspecific differences in fruit-foraging were manifested in preferences for different plant genera, often associated with different habitats. No evidence was found for spatial partitioning of the same fruit species. Interspecific overlap in fruit-for- aging was 3× higher than that in arthropod-foraging, and species of Tangara that frequently joined the same mixed-species flocks differed largely in arthropod-foraging but overlapped greatly in fruit-foraging. The differences in patterns between arthropod and fruit-foraging may be explained by the different characteristics of arthropods and fruits as food resources. High sympatry of species of Tangara and other omnivorous tanagers, in general, appears to be maintained not because fruits are abundant, resulting in little competition for them, but because these tanagers specialize on different microhabitats for foraging arthropods.Segregación de Artrópodos como Recurso Alimenticio de Tangaras Omnívoras (Tangara spp.) en el Oeste de Ecuador
Reassessing the Cowbird Threat
Authors: Zanette Liana , Haydon Daniel T. , Smith James N. M. , Taitt Mary J. , Clinchy Michael 
Published: September 2019

AbstractThe demographic significance of parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds”) has been debated for years, because manipulative studies are few and mathematical models of cowbird-host systems have not led to tests of their predictions. We combine results from a cowbird- removal experiment (Smith et al. 2002, 2003) with a stochastic simulation model that we developed, to reassess the effect of cowbirds on the annual reproductive success (ARS) and nesting success in Song Sparrows (Melospiza melodia). Our model followed the breeding success of individual Song Sparrow nests and extrapolated to output variables including ARS, nest survival, and parasitism rates. We parameterized the model with field data from cowbird control sites (i.e., cowbirds not manipulated) and found that output variables matched those observed. We used the reduced parasitism rates observed on cowbird-removal sites, reran the model, and compared output with observed values. On removal sites, ARS was greater than predicted by the model, which indicates that the model failed to account for some biological phenomenon that occurred when cowbirds were in the system. To assess what this phenomenon might be, we conducted further analyses that indicated that cowbirds may facilitate nest predation by “conventional” predators. Using elasticity analyses, we show that cowbirds have their largest effect on ARS through egg removal and that conventional predators are more important than cowbirds in directly affecting nest survival rates. We report that to assess the effect of cowbirds on nest survival, researchers must avoid using the common technique of comparing survival rates of parasitized and unparasitized nests within populations.Réévaluation de la Menace du Vacher
Vigilance Behavior in the Harlequin Duck (Histrionicus Histrionicus) During the Preincubation Period in Labrador: Are Males Vigilant for Self or Social Partner?
Authors: Squires Kelly A. , Martin Kathy , Goudie R. Ian 
Published: September 2019

AbstractMales of several avian species are more vigilant than their female partners, particularly during the preincubation period. Male vigilance may function as a deterrent of extrapair copulation attempts (EPCs) or to ensure male survival, because males of sexually dimorphic species may be more conspicuous to predators than females. However, vigilant males may act as antipredator sentinels to enhance female survivorship, which may also allow females to feed and rest more efficiently, thereby enhancing their ability to form clutches. We attempted to distinguish between the “male benefits” and “female benefits” hypotheses by studying the behavior of unpaired males and paired Harlequin Ducks (Histrionicus histrionicus) during the preincubation period. Paired males were, on average, four times more vigilant than unpaired males and their mates, which suggests that elevated levels of vigilance by paired males does not function primarily for self-protection against predators. Males were not more vigilant during the female’s fertile period, contrary to the “paternity assurance” hypothesis. Male vigilance during feeding bouts was highest when pairs fed alone near shore—a condition in which feeding was likely more “risky.” Male vigilance was positively correlated with female feeding when females fed near shore, but not at other times. During resting bouts, males were vigilant 14 ± 0.01% of the time in all conditions. We suggest that male vigilance may be important to enhance female survival, especially when females feed under risky conditions.Comportement de Vigilance chez Histrionicus histrionicus durant la Période de Pré- incubation au Labrador: Les Mâles Sont-ils Vigilants pour Eux-mêmes ou pour leur Partenaire Social?
Return Rate, Fidelity, and Dispersal in a Breeding Population of Flammulated Owls (Otus Flammeolus)
Authors: Linkhart Brian D. , Reynolds Richard T. 
Published: September 2019

AbstractWe estimated annual return rate, fidelity, and breeding dispersal in a migratory population of Flammulated Owls (Otus flammeolus) in central Colorado. Return rates, based on capture-recapture histories of 39 males and 52 females from 1981 to 2003, were higher for males (84%) than for females (45%). Annual recapture probability was higher for females, because breeders are easier to capture than nonbreeders and females always attempted to nest, whereas some males were unpaired (did not nest) for up to four years. Territory fidelity was male biased (92%, vs. 56% for females, adjusted for undetected emigration), and mean tenure on territories was more than twice as long for males as for females. Females, but not males, had lower return rates to territories in the year following nesting failure compared with females whose nests were successful. Most males appeared to occupy one territory their entire reproductive lives, countering predictions of habitat-selection models that individuals should move to higher-quality habitats when they become available. We estimated that 74% of pairs retained the same mate in consecutive nesting attempts, but mates that bred together for multiple years had no reproductive advantages over mates that bred together for the first time. In most cases, females dispersed from territories if their mates did not return. When females dispersed, they went to territories where total productivity over the study and lifetime reproductive success of new mates were higher than on original territories, which supports the hypothesis that dispersal by females increases individual fitness.Tasa de Retorno, Fidelidad y Dispersión en una Población Reproductiva de Otus flammeolus
Annual Variation in the Benefits of a Nesting Association Between Red Phalaropes (Phalaropus Fulicarius) and Sabine's Gulls (Xema Sabini)
Authors: Smith Paul A. , Gilchrist H. Grant , Smith James N. M. , Nol Erica 
Published: September 2019

AbstractBy nesting near aggressive birds, timid species can reap the benefits of aggressive nest defense while avoiding the costs. Red Phalaropes (Phalaropus fulicarius; hereafter “phalaropes”) typically nest in grass-sedge marshes, but nests have also been noted in rocky coastal habitats. We studied the reproductive ecology of phalaropes at East Bay, Southampton Island, Nunavut, to determine whether their use of coastal nest areas reflected a protective nesting association with an aggressive larid, the Sabine's Gull (Xema sabini; hereafter “gull”). From 2000 to 2002, we found and monitored 29 phalarope nests with gull nests nearby (≤150 m away) and 26 without gulls nearby. Coastal phalarope nests were nearer to gull nests than expected by chance. No habitat differences were detected between coastal areas with and without gull nests, but only three phalarope nests were found in coastal areas without gull nests. Thermistor probes inserted in phalarope nests revealed that incubators with gulls nearby behaved less cryptically, taking more frequent and longer incubation recesses. In human-approach experiments, phalaropes with gulls nearby flushed earlier than those without gulls. In 2000 and 2001, hatch success was 17–20% higher for phalaropes with gulls nearby, but these nests had lower success rates than those without nearby gulls in 2002. These gulls are able to defend their nests from avian predators only; in 2002, arctic foxes (Alopex lagopus) were abundant, and their primary prey, collared lemmings (Dicrostonyx torquatus), were scarce. We suggest that phalaropes select coastal areas near gulls, but that this association is beneficial to phalaropes only in years when egg predation by arctic foxes is low.Variation Annuelle des Bénéfices d'une Association pour Nicher entre Phalaropus fulicarius et Xema sabini
Plumage Development and Molt in Long-Tailed Manakins (Chiroxiphia Linearis): Variation According to Sex and Age
Authors: Doucet Stéphanie M. , McDonald David B. , Foster Mercedes S. , Clay Rob P. 
Published: September 2019

AbstractLek-mating Long-tailed Manakins (Chiroxiphia linearis) exhibit an unusual pattern of delayed plumage maturation. Each year, males progress through a series of predefinitive plumages before attaining definitive plumage in their fifth calendar year. Females also exhibit variation in plumage coloration, with some females displaying male-like plumage characteristics. Using data from mist-net captures in northwest Costa Rica (n = 1,315) and museum specimens from throughout the range of Long-tailed Manakins (n = 585), we documented the plumage sequence progression of males, explored variation in female plumage, and described the timing of molt in this species. Males progressed through a series of age-specific predefinitive plumages, which enabled the accurate aging of predefinitive-plumaged males in the field; this predefinitive plumage sequence is the basis for age-related status-signaling in these males. Females tended to acquire red coloration in the crown as they aged. However, colorful plumage in females may be a byproduct of selection on bright male plumage. Females exhibited an early peak of molt activity from February to April, little molt from May through July, and a second, more pronounced peak of molt activity in October. By contrast, males in older predefinitive-plumage stages and males in definitive plumage exhibited comparable unimodal distributions in molt activity beginning in June and peaking between July and October. Our data are consistent with selective pressure to avoid the costs of molt-breeding overlap in females and older males. Our findings have important implications for social organization and signaling in Long- tailed Manakins, and for the evolution of delayed plumage maturation in birds.Desarrollo del Plumaje y Muda en Chiroxiphia linearis: Variación de Acuerdo al Sexo y la Edad
Density, Territory Size, and Long-Term Spatial Dynamics of a Guild of Terrestrial Insectivorous Birds Near Manaus, Brazil
Authors: Stouffer Philip C. 
Published: September 2019

Abstract
From 1994 to 2003, I annually surveyed terrestrial insectivorous birds in a 100-ha plot within continuous rainforest near Manaus, Brazil. I used spot-map registrations and radiotagged birds to estimate territory size and density on the plot for 13 species. As in the few previous studies of Amazonian birds, territory sizes were large (mean = 13.0 ha) and densities were low (mean = 3.4 pairs per 100 ha). The most common species, Formicarius colma, was the only species with >10 pairs per 100 ha, and one of four species (with Myrmeciza ferruginea, Conopophaga aurita, and Corythopis torquatus) to have territories of <7.0 ha. On average, each species occupied 34% of the plot, with only four species (F. colma, Grallaria varia, F. analis, and M. ferruginea) ever occupying >50% in any year. Territories appeared and disappeared between surveys; ∼71% of territories detected in a given survey were present in the next survey. The two rarest species, Myrmothera campanisona and Hylopezus macularius, were absent from the plot in some years. Across species, territory stability was positively correlated with abundance; more common species had more stable density among years than rare species. Although past research has shown territory stability for the most common species of Neotropical rainforest birds, my results suggest that rarer species, which constitute the bulk of the avifauna, may show greater fluctuation in abundance.
I compared my results to similar data from lowland rainforests in Panama, French Guiana, Ecuador, and Peru. Species richness was lowest in Panama, but comparable among the Amazonian sites. Panama also had the highest biomass and smallest territory sizes. Interestingly, relative abundances of species shared among sites were not necessarily similar. With the exception of Conopophaga spp., all species or replacement species shared among sites were at least twice as abundant at one site as at another. Relative abundance within genera also differed among sites for Sclerurus and Formicarius. The sparse data available so far suggest that individual species show considerable spatial variation in abundance across Amazonia, though the mechanisms and the texture of the patterns remain unknown.
Densidade, Tamanho do Território, e Dinamismo Espacial ao Longo Prazo das Aves Insetívoras Terrestres perto de Manaus, Brasil
Egg Size, Eggshell Porosity, and Incubation Period in the Marine Bird Family Alcidae
Authors: Zimmermann Karen , Hipfner J. Mark 
Published: September 2019

AbstractAlthough the ultimate factors that influence the duration of avian incubation periods are well known, we know much less about the proximate mechanisms by which birds adjust incubation period in response to selection. We tested the hypothesis that an adjustment in eggshell porosity is one such proximate mechanism (i.e., that avian species with higher ratios of incubation period to egg size lay eggs with less porous shells). Eggshell porosity affects the rate of gaseous exchange between the developing embryo and the external environment; thus, to the extent that embryonic metabolism is diffusion-limited, eggshell porosity could directly determine incubation period. To test that hypothesis, we collected eggs from seven species of Alcidae, a family of marine birds that exhibits an unusual degree of interspecific variation in incubation period, and measured egg mass and eggshell porosity (determined by the number and size of pores and the thickness of the shell). Incubation periods were obtained from the literature. Egg mass and eggshell porosity combined explained 87% of the variation in incubation period among the seven species, which included at least one member of each of the six main alcid lineages. As predicted, eggshell porosity and incubation period were negatively related, after controlling for egg mass. Our results are consistent with the hypothesis that evolutionary changes in avian incubation period may be attributed, at least in part, to adjustments in eggshell porosity.Taille de l’Œuf, Porosité de la Coquille et Période d’Incubation chez les Oiseaux Marins de la Famille des Alcidés
Ecological Role of a Tree (Gmelina Arborea) Plantation in Guatemala: An Assessment of an Alternative Land use for Tropical Avian Conservation
Authors: Rotenberg James A. 
Published: September 2019

AbstractEstablished parks and nature reserves may be inadequate to preserve long-term biotic diversity, especially in tropical regions of Latin America where anthropogenic disturbance and land-conversion is an ongoing problem. Demand for economically productive land uses, such as cattle pastures or monoculture plantations, is one of the greatest threats to habitat and wildlife preservation. As a result, conservation biologists have turned to examining attributes of nonprotected lands to determine which land uses both support wildlife and make economic sense. I examined bird use of a plantation of Gmelina arborea (“white teak” or “melina” trees; hereafter “plantation”) in Guatemala to assess its suitability as bird habitat. Gmelina arborea is grown mainly for wood and paper pulp. Several compositionally different habitats were identified, based on the amount of natural vegetation grown within and among the plantation trees, forming a heterogeneous landscape. I detected 195 bird species from 45 families within this plantation-dominated landscape, and 144 species in plantation habitats combined. I observed a positive association between increased vegetative complexity and bird species richness; moreover, bird species richness attained levels statistically indistinguishable from those found in nearby forest fragments. Mixed plantation habitat containing 19–31% natural vegetative coverage supported bird communities that equaled or surpassed levels of species richness found by other researchers in shaded coffee (Coffea spp.) plantations. However, pure stands of G. arborea supported richness levels equal to those of grazed pasture; diversity levels associated with both these land uses were close to those reported for sun coffee plantations. Clearly, native vegetation played a significant role in enhancing bird species richness in the plantation habitat, and amounts of relative cover similar to or exceeding those in the plantation I studied should be considered in any management plan for G. arborea in Central America.Rol Ecológico de Plantaciones de Árboles de Gmelina arborea en Guatemala: Una Evaluación de un Uso Alternativo del Suelo para la Conservación de las Aves Tropicales
Testosterone in Northern Cardinals (Cardinalis Cardinalis): Possible Influence of Prolonged Territorial Behavior
Authors: Jawor Jodie M. 
Published: September 2019

Abstract
Two attributes of many temperate passerine species are short-term territoriality and strongly fluctuating annual testosterone (T) profiles. Circulating T of temperate passerines can vary from undetectable levels in the nonbreeding season to higher, but fluctuating, levels during the breeding season. Males of many temperate species respond to territorial instability during the breeding season with transitory increases in T. In females, the hormonal response to aggression is more complex. Most temperate-zone passerine species that have been studied exhibit territoriality for less than three months. Here, I describe the year-round T profile of male and female Northern Cardinals (Cardinalis cardinalis), a temperate-zone species with prolonged territorial behavior (7+ months). Circulating levels of T in female Northern Cardinals is relatively stable. Males show variation in T levels over the year and they may respond to territorial intrusions with increases in T. Of particular interest are the relatively high levels of T observed in female Northern Cardinals throughout the year, and measurable amounts of T in both sexes in the winter.
Testosterona en Cardinalis cardinalis: Posible Influencia del Comportamiento Territorial Prolongado
High Level of Song Sharing in an Eastern Population of Song Sparrow (Melospiza Melodia)
Authors: Foote Jennifer R. , Barber Colleen A. 
Published: September 2019

Abstract
Using shared songs is believed to be an integral part of neighbor communication and territory establishment strategies among many avian species with repertoires. Previous studies of two western subspecies of Song Sparrows (Melospiza melodia) reported a high level of song sharing among neighboring males, whereas studies of an eastern subspecies have reported a very low level. The purpose of our study was to investigate another population of the eastern subspecies to determine whether higher song-sharing levels existed within its range. Every song in the repertoire of 29 males was compared with the songs of all other males to assess the number of shared songs. For each male, we calculated the mean song-sharing level with neighbors and non-neighbors. Males shared, on average, 33% of their repertoire with neighbors, significantly more than they shared with non-neighbors (27% of their repertoire). Two first-year males learned whole song types from several individuals and preferentially learned the song types shared among those individuals. Our results suggest that the eastern and western subspecies may not differ genetically in the way they learn songs, because song-sharing levels and song learning in our population were more similar to those of the western subspecies than to those of other populations within its own subspecies. Song-sharing differences among eastern populations may be explained instead by factors acting at the level of individual populations.
Niveau Élevé de Chants Partagés chez une Population de l'Est de Melospiza melodia