bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of Predators and Offspring Influence Nest Defense by Arctic and Common Terns
Authors: Whittam Rebecca M. , Leonard Marty L. 
Published: September 2019

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

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

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

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

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

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

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

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

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

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

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

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

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

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

AbstractWe studied recruitment and dispersal of White-tailed Ptarmigan (Lagopus leucurus) breeding in naturally fragmented alpine habitats at four study sites in Colorado from 1987–1998. Almost all recruitment for both sexes, particularly females, was of birds produced outside local populations and also external to nearby studied populations. Populations were more dependent on female recruitment than on male recruitment to sustain them, and patterns of recruitment were not correlated with local survival of adults or production of young the previous year, except at one site for females. Over 95% of recruits were yearlings. Breeding dispersal of adults, an infrequent but regular event, was also important to inter-population connectivity. Our data for multiple populations allowed us to describe movement patterns among populations to assess consistency with conditions required for a rescue system. After widespread reproductive failure in one year, we expected all populations the next year would have low recruitment due to a reduced supply of recruits produced in the region. Recruitment was low, but impact varied among populations. We conducted an over-winter study of radio-marked offspring to determine possible influences of winter site location and relatives on recruitment patterns. Contrary to expectation, offspring remained on or near breeding sites in winter, but were not located near their mothers or siblings. Recruitment location was related to winter site location. White-tailed Ptarmigan exhibit a well developed capacity for external recruitment that allows them to persist in small populations with stochastic conditions for breeding and survival. Extensive external recruitment may be a general pattern for birds.
Seasonal Migration and Genetic Population Structure in House Wrens
Authors: Arguedas Nidia , Parker Patricia G. 
Published: September 2019

AbstractNeotropical migrant birds have undergone significant changes in population size, due in part to alterations in the landscape in their breeding range. Some alterations have resulted in the isolation of areas containing optimal habitat for breeding. Isolation between habitat fragments could reduce gene flow between populations, which might result in loss of genetic variation due to genetic drift. To test whether isolation due to distance between populations may affect migratory birds as much as sedentary birds, we used four microsatellite loci as genetic markers to compare gene flow and population structure in migratory and sedentary House Wrens (Troglodytes aedon and T. musculus, respectively). If migratory behavior enhanced gene flow, we expected to find that populations of migratory birds were genetically more similar than populations of sedentary birds, and that gene flow declined more rapidly with distance in sedentary than in migratory populations. Blood samples were collected from 18–25 migratory House Wrens at each of six sites in Ohio separated by distances from 25 to over 300 km, and from 16–20 sedentary House Wrens at each of six sites in Costa Rica, also at distances up to 350 km. We used heterologous microsatellite primers to obtain estimates for RST (population subdivision) and Nm (number of immigrants per generation) in relation to distance between pairs of populations. In the migratory populations, Mantel permutational tests showed no effect of distance on RST or Nm at distances between 25 and 300 km. In the sedentary birds, RST increased and Nm decreased significantly as distance between populations increased from 25 to 300 km. FST values were not different from those obtained using Slatkin's (1995) RST statistics. These results are consistent with our hypothesis that migratory behavior enhances gene flow.
Use of Arboreal Termitaria by Nesting Birds in the Peruvian Amazon
Authors: Brightsmith Donald J. 
Published: September 2019

AbstractI documented the use by nesting birds and availability of arboreal termite nests (termitaria) in the Peruvian Amazon. Birds occupy about 1% of the termitaria annually, suggesting that termitarium availability does not limit reproductive output. Birds choose termitaria that are larger and higher than average, and the three most common termitarium-nesting species differ in their use of termitaria. Two species of Brotogeris parakeets use termitaria with similar characteristics, but Tui Parakeets (B. sanctithomae) nest in young forests and edge habitats whereas Cobalt-winged Parakeets (B. cyanoptera) use mature forests. Termitaria used by Black-tailed Trogons (Trogon melanurus) are larger and lower than those used by the two Brotogeris species. The contention that birds usually nest in termitaria still occupied by termites was upheld, but the presence or absence of termites did not explain a significant proportion of the difference between used and available termitaria after removing the effects of height, volume, and substrate type. Birds choose to nest in termitaria inhabited by both termites and aggressive biting ants (Dolichoderus sp.). These ants may be protecting the birds' nests by attacking predators or by providing a sort of “olfactory camouflage.”