bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lilac-Crowned Parrot Diet and Food Resource Availability: Resource Tracking by a Parrot Seed Predator
Authors: Renton Katherine 
Published: September 2019

AbstractThe pattern of food resource availability and use by Lilac-crowned Parrots (Amazona finschi) was evaluated in tropical dry forest of the Reserva de la Biosfera Chamela-Cuixmala, western Mexico. Monthly fruiting phenology transects were conducted throughout the year in deciduous and semi-deciduous forest to determine temporal and spatial variability in resource abundance. Resource use by parrots was evaluated through observations of diet and habitat use. There was significant temporal and spatial variability in food resource abundance, with semi-deciduous forest providing greater food resources for parrots during the dry season, whereas food resource abundance increased in deciduous forest during the rainy season. The critical period of food resource scarcity occurred during May–June at the end of the long dry season. Lilac-crowned Parrots were pre-dispersal seed predators, and exhibited high flexibility in diet, incorporating dietary switching, as well as niche-breadth contraction and expansion, which corresponded with temporal variations in food resource availability. There was low overlap in parrot diets between seasons, with parrots exhibiting a narrow food niche-breadth during the late dry season when resource availability declined. Parrots also demonstrated spatial variation in habitat use, corresponding to fluctuations in the availability of food resources in different habitats. This flexibility in foraging enables parrots to closely track and exploit seed resources which exhibit high temporal and spatial variability in abundance.
Diet and Hunting Behavior of the Crane Hawk in Tikal National Park, Guatemala
Authors: Sutter Jason , Martínez A. Walter E. , Oliva T Francisco , Oswaldo J Nery , Whitacre David F. 
Published: September 2019

AbstractWe studied the breeding diet and hunting behavior of Crane Hawks (Geranospiza caerulescens) in Tikal National Park, Petén, Guatemala in 1994 and 1995. We observed 227 prey items while conducting observations at six nesting attempts, and during opportunistic sightings in the breeding season. Among 181 identified prey items, rodents comprised 47.5%, lizards 19.9%, frogs 16.0%, bats 6.6%, birds 6.1%, and snakes 2.8%; a juvenile skunk also was represented. Rodents accounted for 77% of estimated biomass, including at least eight species representing terrestrial, cursorial, and arboreal habits. More than half of all prey items weighed <20 g, but 40% weighed >50 g; many were nocturnal species presumably taken from daytime hiding places. We observed hunting attempts in all strata of the forest and in several forest types. Hunting behavior included still-hunting from a perch and probing with head or feet in holes, bromeliads and other epiphytes, palm leaf axils, crotches of branches, behind bark in living and dead trees, and in puddles. Compared to other raptors studied at Tikal, the Crane Hawk had a moderately broad food niche that overlapped most with other raptors deemed dietary generalists. However, the Crane Hawk's unique anatomical features and hunting behavior enabled it to capture diurnally reclusive prey presumably unavailable to many other raptors, thus facilitating relatively low dietary overlap.
A New Specimen of the Tiny Middle Eocene Bird Gracilitarsus Mirabilis (New Family: Gracilitarsidae)
Authors: Mayr Gerald 
Published: September 2019

Abstract
A new, second specimen of the tiny Middle Eocene bird Gracilitarsus mirabilisMayr 1998 shows several previously unknown osteological features. The species represents a bauplan unknown among recent birds in that it combines swallow-like length proportions of the major wing bones with a long and slender tarsometatarsus. The feet of Gracilitarsus mirabilis are highly unusual in that the three anterior toes are very short and of nearly equal length, and in that the claws are of great dorso-ventral depth. Gracilitarsus mirabilis is classified within a new family in this study. The species shares some derived characters of the tarsometatarsus with the Paleocene South American species Eutreptodactylus itaboraiensisBaird and Vickers-Rich 1997.
Does Risk of Nest Failure or Adult Predation Influence Hatching Patterns of the Green-Rumped Parrotlet?
Authors: Stoleson Scott H. , Beissinger Steven R. 
Published: September 2019

Abstract
Parent birds may adjust the onset of incubation to minimize periods of high risk of nest failure due to predation (the Nest Failure Hypothesis) or of mortality to adult birds (the Adult Predation Hypothesis). We examine temporal patterns of risk of nest failure and predation on adult females in a population of Green-rumped Parrotlets (Forpus passerinus) to determine whether those patterns explain observed patterns of incubation. Over one-third of nests (38.6%) failed completely, and an additional 2.2% failed after fledging one or more young. Most nests failed due to predation and infanticide. Because parrotlets begin incubation on the first egg, we examined a range of hypothetical failure rates for the period prior to the onset of incubation. Daily survival probabilities for nests were higher during the nestling stage than during incubation or fledging. Survival of adult females varied little through the nesting cycle, but was highest while attending nestlings. Model predictions were highly dependent on assumptions made about survival rates during the pre-incubation period. When empirically based values were used for this period, maximum productivity was achieved with first-egg incubation, consistent with observed patterns. Models were most sensitive to those parameters most difficult to estimate. This study represents the first test of the Nest Failure model with a nonpasserine or tropical species, and the first assessment of the Adult Predation model using field data.
Pathogenicity, Serological Responses, and Diagnosis of Experimental and Natural Malarial Infections in Native Hawaiian Thrushes
Authors: Atkinson Carter T. , Lease Julie K. , Drake Beth M. , Shema Nicholas P. 
Published: September 2019

AbstractOmao (Myadestes obscurus) from the Hawaiian Islands typically have very low prevalences of infection with avian malaria (Plasmodium relictum) and it is not clear whether they share the same high susceptibility to this parasite that has been documented in native Hawaiian honeycreepers. We exposed four captive Omao to single infective mosquito bites and measured parasitemia, serological responses, and mortality over time. All four birds experienced transient infections with low parasitemias and were immune when rechallenged with multiple infective mosquito bites. By contrast, three of four honeycreepers (Maui Alauahio, Paroreomyza montana) that were exposed to the same dose and parasite isolate succumbed to infection. All four Omao developed antibodies to a common suite of malarial antigens that were detectable on immunoblots of a crude red blood cell extract of P. relictum. We used this technique to screen plasma samples from wild Omao and endangered Puaiohi (Myadestes palmeri) that were captured at elevations between 900 and 1300 m on the islands of Hawaii and Kauai. We found that the true prevalence of infection at elevations where active malaria transmission occurs is much higher than estimates based on blood smears alone. Hawaiian thrushes appear to have a high tolerance for malaria, with most individuals developing chronic, low-level infections after exposure that cannot be diagnosed accurately by blood smears.
Radar-Based Monitoring of Marbled Murrelets
Authors: Cooper Brian A. , Raphael Martin G. , Mack Diane Evans 
Published: September 2019

Abstract
We used radar to measure daily, monthly, and annual patterns of Marbled Murrelet (Brachyramphus marmoratus) abundance and movements at 12 major river valleys in the Olympic Peninsula of Washington. Landward movements of murrelets peaked from ∼75 min to ∼20 min before sunrise, followed by a seaward exodus from ∼20 min before sunrise to ∼65 min after sunrise. This general pattern of a landward movement followed by a seaward exodus varied little, but the timing of the seaward exodus gradually became later from May to July. Within a morning, numbers of landward radar targets averaged twice the numbers of seaward targets, and morning counts were approximately five times evening counts. Species identification error rates were lower for landward radar counts than for seaward counts. Radar counts varied through the season, with numbers increasing from May to July, then dropping in August. Seaward counts were more variable than landward counts. There was wide overlap among months in the amount of daily variation in both landward and seaward counts. Radar appears to be a powerful, cost-effective, and non-intrusive tool that can establish an index of abundance for murrelets at specific inland breeding areas.
Movements, Habitat Use, and Survival of Nonbreeding Piping Plovers
Authors: Drake Katherine R. , Thompson Jonathan E. , Drake Kiel L. , Zonick Curt 
Published: September 2019

AbstractWe studied movements, habitat use, and survival rates of 49 radio-marked Piping Plovers (Charadrius melodus) overwintering along the southern Laguna Madre of Texas during 1997–1998. Plovers exhibited strong site fidelity to nonbreeding areas throughout fall, winter, and spring. Mean home-range size of plovers (based on 95% of locations) was 12.6 km2 with a mean core area (50% of locations) of 2.9 km2. Seasonal home-range size and core areas differed only between fall and winter; home-range and core areas were smaller in fall than winter. Mean linear distance moved was 3.3 km; fall movements were smaller than those made in winter and spring. Habitat use varied seasonally: plovers used algal flats more during fall and spring than during winter; plovers used exposed sand flats more often during winter than in fall and spring. We recorded no mortality of radio-marked birds. High rates of survival and strong site fidelity throughout the nonbreeding period suggest that this period of the annual cycle may not contribute to the declining population size for Piping Plovers wintering in this region. However, because Piping Plovers spend most of the annual cycle on nonbreeding areas, they are likely to be negatively affected by loss of those sites, emphasizing the importance of conserving nonbreeding areas for this threatened and endangered species.
Habitat Preferences of Pinyon-Juniper Specialists Near the Limit of Their Geographic Range
Authors: Pavlacky David C. , Anderson Stanley H. 
Published: September 2019

Abstract
We investigated habitat preferences for five pinyon-juniper specialists during the 1998 and 1999 breeding seasons in Utah juniper (Juniperus osteosperma) woodlands of southwestern Wyoming. We compared avian use and availability of vegetation features using univariate and multivariate analysis to detect selection for vegetative features of pinyon-juniper specialists near the northeastern range boundary of pinyon-juniper habitat on the Colorado Plateau. Gray Flycatchers (Empidonax wrightii), Juniper Titmice (Baeolophus griseus), and Bewick's Wrens (Thryomanes bewickii) preferred woodlands with high overstory juniper cover. The Juniper Titmouse was associated with senescent trees, Blue-gray Gnatcatcher (Polioptila caerulea) with rock outcrops and shrubs in the family Rosaceae, and Black-throated Gray Warbler (Dendroica nigrescens) with pinyon pine (Pinus edulis). We suggest the geographic distribution of four of five pinyon-juniper specialists is limited by the occurrence of pinyon pine in semiarid woodlands on the northeastern Colorado Plateau. The geographic limit for Blue-gray Gnatcatchers in this region may correspond to the presence of mountain mahogany in the woodland understory. The conservation of pinyon-juniper specialists in southwestern Wyoming will benefit from the maintenance of successional processes, particularly those that perpetuate mature woodlands with a pinyon pine component.
Transect Surveys of Columbid Nests on Puerto Rico, Vieques, and Culebra Islands
Authors: Rivera-Milán Frank F. 
Published: September 2019

Abstract
I conducted transect surveys of pigeon and dove (Columbidae) nests on Puerto Rico, Vieques, and Culebra islands. Nest detection probability and density differed between study areas in January–August 1991 and 1992. Nest detection probability and density did not differ between years or among species, so I used transect data from a larger study (1986–1999) to assess the relationships between nest density and rainfall, food abundance, food diversity, and predator abundance along transects. Food abundance was the most important predictor of annual changes in nest density on the surveyed transects in mesic and xeric habitats during May–June 1986–1999. Positive correlations of annual nest density estimates suggested parallel responses among columbid species to similar or covarying resources in mesic and xeric habitats.
Movement Patterns of Adult Male Ovenbirds During the Post-Fledging Period in Fragmented and Forested Boreal Landscapes
Authors: Bayne Erin M. , Hobson Keith A. 
Published: September 2019

Abstract
Movement of forest songbirds among isolated forest patches following breeding represents an important but poorly understood component of landscape ecology and metapopulation theory. Using radio-telemetry, we followed 44 male Ovenbirds (Seiurus aurocapillus) during the post-fledging period to determine if movement patterns differed in landscapes dominated by agriculture versus those dominated by forest. No differences in home-range size, mean distance moved per day, or maximum distance moved were observed for males captured in a forested landscape vs. those captured in forest fragments in an agriculturally dominated landscape. Male Ovenbirds observed with young moved less than males without young and rarely crossed open gaps. Individuals that failed to breed moved more extensively than successful breeders, possibly in an effort to find new territories for use in future breeding seasons.
Sex Ratios of Dunlin Wintering at Two Latitudes on the Pacific Coast
Authors: Shepherd Philippa C. F. , Lank David B. , Smith Barry D. , Warnock Nils , Kaiser Gary W. , Williams Tony D. 
Published: September 2019

AbstractLatitudinal clines in sex ratio during the nonbreeding season occur in some shorebirds of the Scolopacidae. We compared populations of nonbreeding Dunlin (Calidris alpina pacifica) from two latitudes along the Pacific flyway: the Fraser River Delta, British Columbia, and Bolinas Lagoon, California, to determine whether, and to what degree, they exhibited sex ratios consistent with a latitudinal cline. Dunlin are plumage monomorphic, so we used a maximum likelihood model to estimate overall and monthly sex ratios for each population based on culmen length distributions. Sex ratios in the Fraser River Delta were corrected for sex differences in habitat use. Monthly sex ratios were similar at the two sites but varied throughout the winter, likely reflecting differences in seasonal movement patterns between the sexes. Both populations showed an overall bias toward males (Fraser = 61% males, Bolinas = 65% males). Since there is no evidence to support the possibility of a skew toward males in C. a. pacifica as a whole, our data are consistent with some form of latitudinal cline in the sex ratio of C. a. pacifica. However, additional data from the Oregon coast, southern California, and Mexico are required to resolve this question. We also tested the hypothesis that mean body size within each sex is larger at the higher-latitude site (Fraser River Delta), but this did not appear to be the case.
Factors Influencing Pair Territoriality in the Juniper Titmouse
Authors: Christman Beth J. 
Published: September 2019

Abstract
Pair territoriality outside of the breeding season is a relatively uncommon pattern of social organization in the Paridae (tits, titmice, and chickadees). Within the territorial parids, pair territoriality appears to be the derived state. Because of this, it is possible to address the question: What favors the evolution of this social system? I assessed factors that may be responsible for inducing pair territoriality in Juniper Titmice (Baeolophus ridgwayi), focusing largely on foraging behavior and predation risk. I found that the diet of Juniper Titmice is distinctive as compared to other tits, with large seeds (juniper and pinyon pine) and acorns making up most of the winter diet instead of arthropods. Time budgets reflected that a large proportion of time is spent handling food. Space use was strongly skewed toward locations that should be relatively safe from predators, both because food is located in such sites and because titmice transport seeds to sheltered sites for processing. Seeds decreased significantly in abundance through the course of the winter. Comparisons with group-living tit species that forage largely on arthropods show differences in time and space use. I conclude that the suite of behaviors associated with foraging on large seeds has shifted the cost-to-benefit ratio of group living for Juniper Titmice relative to other tits.
Effect of Group Size on Field Metabolic Rate of Arabian Babblers Provisioning Nestlings
Authors: Anava Avner , Kam Michael , Shkolnik Amiram , Degen A. Allan 
Published: September 2019

Abstract
Arabian Babblers (Turdoides squamiceps; adult body mass 65–75 g) are territorial, cooperatively breeding passerines that inhabit hot, dry deserts. Groups include breeding adults and helpers and generally consist of 3 to 5 individuals (range 2 to 22). All group members provision nestlings at similar rates, and individual visitation rates decline with increasing group size. Consequently, we predicted that the field metabolic rate (FMR) of individuals provisioning nestlings would decrease with increasing group size. To test this prediction, we determined FMR of primary female, primary male, female helper and male helper babblers in different sized groups provisioning nestlings. Field metabolic rate of primary females, but not other classes, decreased linearly with group size. This energy savings could allow primary females in larger groups to start a new nest more quickly. FMR for all babblers was 61% to 66% of the value predicted for a passerine of its body mass provisioning nestlings and was 3.11 × BMR, similar to the mean value of 3.13 × BMR reported for a number of terrestrial species.
Effects of Anthropogenic Food Sources on Movements, Survivorship, and Sociality of Common Ravens in the Arctic
Authors: Restani Marco , Marzluff John M. , Yates Richard E. 
Published: September 2019

AbstractWe investigated survivorship, movements, and sociality of Common Ravens (Corvus corax) exploiting concentrated food resources at a landfill in Greenland. From 1992–1995 we banded 383 ravens: 365 were captured at the landfill and 18 were banded in nearby nests. Thirty-nine ravens were recovered, most by shooting (87%). Mean number of days survived post-banding (494 ± 97) did not differ among age groups, but a higher proportion of juveniles was recovered. Ravens migrated west and south to the coast during winter. No difference existed among age groups in mean distance between locations of banding and recovery (151 ± 31 km). Number of ravens congregating at the landfill declined during the study, coinciding with a decrease in the local human population. Harsh winter climate, limited ice-free land, and abundant human refuse influenced raven use of the wilderness landscape by facilitating the formation of large, nomadic foraging groups.
Species and Sex-Biased Predation on Hatchling Green Turtles by Frigatebirds on Europa Island, Western Indian Ocean
Authors: Lagarde Frédéric , Corre Matthieu Le , Lormeé Hervé 
Published: September 2019

Abstract
Europa Island is a major breeding place for green turtles (Chelonia mydas; 0.7 to 2.4 million juvenile turtles hatch there annually), Great Frigatebirds (Fregata minor; 700 to 1100 breeding pairs), and Lesser Frigatebirds (Fregata ariel; 1000 to 1200 pairs). By visual observation, we quantified the proportions of males, females, and juveniles of both frigatebird species prospecting over the hatching sites and preying on hatchling turtles. Of 1828 juveniles observed hatching at daytime (35 separate turtle emergences), 1632 were immediately eaten by male Great Frigatebirds. Only 10 hatchlings were preyed upon by female Great Frigatebirds; the remaining 186 were captured by juvenile Great Frigatebirds. Such feeding behavior was not observed in Lesser Frigatebirds. We suggest that the sexual and species differences in hatchling turtle predation are due to size differences between the two species and between male and female Great Frigatebirds.
Is Spizella Taverneri a Species or a Subspecies?
Authors: Mayr Ernst , Johnson Ned K. 
Published: September 2019

AbstractBased on distributional, ecologic, morphologic, and vocal data, Klicka et al. (1999) argued in favor of species status for the form taverneri, long regarded as a subspecies of the Brewer's Sparrow (Spizella breweri). For several reasons we disagree with their conclusion: lack of evidence for the reproductive isolation of taverneri from breweri, loss of information on the close relationship and allopatric distribution of the two taxa that would accompany their elevation to species, and violation of the principle of taxonomic balance. Until the demonstration of vocal or display differences relevant to pair formation and maintenance, taverneri and breweri are best regarded as reproductively compatible subspecies.