bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Initial Refueling Rate at Stopover Sites: A Methodological Effect?
Authors: Schwilch Regine , Jenni Lukas 
Published: September 2019

Abstract
For various reasons, migrating birds may not refuel and gain mass immediately after they have arrived at a stopover site. That led to the concept of a search-settling time after arrival with a low or negative initial refueling rate, but its existence has not been clearly demonstrated in field studies. Body-mass changes resulting from capture–recapture data can be misleading if used for the estimation of a natural low initial refueling rate because (1) it is usually unknown whether the day of first capture is also the first day of stopover, and (2) handling at first capture may have an adverse effect on subsequent body-mass development. To circumvent those problems we increased probability of catching birds shortly after arrival by inducing landfall by tape-luring, and we estimated body-mass change without previous handling effects from concentration of two metabolites in blood plasma. In the Eurasian Reed-Warbler (Acrocephalus scirpaceus) studied at a stopover site in Switzerland, there was no difference in plasma-metabolite concentrations between a group of mostly newly arrived individuals and a group with few newly arrived birds. Similarly, there was no difference in those parameters between birds that had been handled before and birds at first capture. However, the analysis of capture–recapture data from two other Swiss stopover sites with longer handling times indicated that mean body mass of Eurasian Reed-Warblers and European Robins (Erithacus rubecula) dropped after capture and reached initial values only after one to several days. We concluded that mass loss after capture depended mainly on lost foraging time and that natural low initial refueling rate after arrival at a stopover site is not detectable under the conditions of this study.
Effect of Conspecific Brood Parasitism on Host Fitness for Tufted Duck and Common Pochard
Authors: Dugger Bruce D. , Blums Peter 
Published: September 2019

Abstract
Brood parasitism occurs disproportionately in birds with precocial young and is particularly common in Anseriformes. In part, that pattern may result because precocial hosts, relative to altricial species, incur relatively few costs when caring for precocial eggs. Empirical data do not consistently support that hypothesis, and some parameters have not been adequately compared between parasitized and nonparasitized nests or females. We used a combination of experimentation (egg and duckling additions) and analysis of a larger observational data set to compare reproductive parameters, recruitment, and adult survival between parasitized and nonparasitized female Common Pochard (Aythya ferina) and Tufted Ducks (A. fuligula). Addition of three eggs to nests during the host's laying cycle had no effect on host clutch size, host egg hatch success, or nest success for either species. Nest success was not affected by parasitism intensity for pochards, but we did detect a small drop in nest success for Tufted Duck nests parasitized with &gt;6 eggs. Recruitment probability did not differ between parasitized and nonparasitized nests for either species, and parasitism had no negative effect on adult survival. Between-year nest initiation dates were later for parasitized Tufted Ducks, although the biological consequences of that difference (3.8 days) seem negligible. Moderate levels of parasitism do not negatively affect hosts for these two species.
Territory and Nest-Site Selection of Cerulean Warblers in Eastern Ontario
Authors: Jones Jason , Robertson Raleigh J. 
Published: September 2019

AbstractWe examined habitat selection by breeding Cerulean Warblers (Dendroica cerulea) at three spatial scales in eastern Ontario over three years (1997–1999). Territories were characterized by well-spaced large trees, with high canopies and dense foliage cover at heights between 12–18 m. Nesting habitat additionally was characterized by dense foliage cover above 18 m. The results of our nest-patch (0.04 ha circle around nest) and nest-site (0.01 ha circle) analyses indicate that male Cerulean Warblers may take active roles in nest-site selection when selecting territories. We conclude from our nest-patch and nest-site selection analyses that territories likely contain multiple nest patches and sites and that male Cerulean Warblers may defend areas with multiple nest patches or sites, which may attract females to settle with them. Whether or not Cerulean Warbler females use nest-site availability as a mate- or territory-choice cue remains unknown. We also tested the validity of a commonly made assumption that a random sampling of habitat by researchers is representative of the habitat actually available to birds and found that, in our study area, the assumption was invalid. Taken together, our results point toward the need to maintain sizeable stands of mature, deciduous forest to ensure the persistence of Cerulean Warblers in eastern Ontario. Population characteristics such as lower minimum area requirements and a resilience to habitat disturbance may make that an easier job in eastern Ontario than elsewhere in this species' breeding range.
Within-season Nest-site Fidelity in Eastern Bluebirds: Disentangling Effects of Nest Success and Parasite Avoidance
Authors: Stanback Mark T. , Dervan Anne A. 
Published: September 2019

AbstractWe manipulated nestbox choices in Eastern Bluebirds (Sialia sialis) to assess (1) whether the presence of a previously used (and presumably parasite-ridden) nest cavity increases or decreases the likelihood of within-season nestbox reuse and (2) whether birds prefer previously successful cavities. Initially, birds were presented with two clean identical nestboxes erected 1 m apart. After the first nesting, we removed nest material from half of the successful box pairs and recorded subsequent nesting choices. Given a choice between a used and an unused box, bluebirds chose the unused but parasite-free cavity significantly more often. Presented with a cleaned successful box and an identical unused one, bluebirds opted to reuse the former significantly more often. Those results suggest that (1) bluebirds recognize a cost of within-season nest reuse and are willing to switch nest sites to minimize parasitism, (2) bluebirds prefer successful cavities, but only if they are clean, and (3) in our population, in which cost of nest switching was minimized, the aversion to parasites was stronger than the preference for successful cavities.
Female Hematozoan Infection Reduces Hatching Success but not Fledging Success in Pied Flycatchers Ficedula hypoleuca
Authors: Sanz Juan J. , Arriero Elena , Moreno Juan , Merino Santiago 
Published: September 2019

AbstractWe report association between female blood parasite prevalence (percentage of infected birds) just after egg laying and reproductive success in two successive breeding seasons, in a breeding population of Pied Flycatcher Ficedula hypoleuca in central Spain. Females infected with Trypanosoma spp. had a higher probability of deserting their clutches during the incubation period than noninfected females. Females infected with Haemoproteus balmorali hatched proportionally fewer eggs than noninfected females. Female infected with H. balmorali during the incubation period may have a decreased ability to thermoregulate which may affect their incubation capacity. Fledging success, breeding success, fledgling mass, and tarsus length were not associated with infection of the mother by blood parasites during the incubation period, suggesting that females and their mates may compensate during the nestling period for the negative effect of blood parasites during the incubation period.
Diving Depths of Shearwaters
Authors: Burger Alan E. 
Published: September 2019

AbstractMaximum diving depths were measured for shearwaters breeding on Cousin Island, Seychelles. Eighty-three percent of 23 Wedge-tailed Shearwaters (Puffinus pacificus) dived, and their mean maximum depth was 14 m (SD = 23 m, range 1–66 m, N = 19). All Audubon's Shearwaters (P. lherminieri) dived, and their mean maximum depth was 15 m (SD = 12 m, range 6–35 m, N = 7). These data contradict the hypothesis that tropical shearwaters should not specialize in underwater foraging. They are capable of exploiting deep prey unavailable to most other tropical seabirds. Five Puffinus species (temperate and tropical) attained allometrically scaled maximum depths comparable to those of penguins and alcids.
Visual Signals for Individual Identification: The Silent “Song” of Ruffs
Authors: Lank David B. , Dale James 
Published: September 2019

AbstractBreeding male Ruffs (Philomachus pugnax) appear to communicate individual identity through extreme variation in coloration and pattern of their plumages. If plumage variation evolved to provide sufficient information to signal individual identity, we might expect different plumage components to vary independently. We find that variation in four plumage characteristics is largely independent. Previous studies produced conflicting answers about plumage-component independence, perhaps because they failed to separate two genetically distinct behavioral categories of males, which differ in plumage types, in their analysis. We propose that using plumage variation to signal individual identity, rather than voice (used by most other bird species) was favored by lengthy daytime male display in open habitats in close proximity to receivers. However, signaling associated with the unique dimorphism in this species' male mating behavior might also have influenced the evolution of extraordinary plumage diversity in this species.
Frequency of Egg and Nestling Destruction by Female Brown-headed Cowbirds at Grassland Nests
Authors: Granfors Diane A. , Pietz Pamela J. , Joyal Lisa A. 
Published: September 2019

AbstractResearchers have suggested that Brown-headed Cowbirds (Molothrus ater) destroy nest contents of potential hosts to induce renesting and thus enhance future opportunities for parasitism. Although cowbird destruction of passerine nests has been witnessed and surmised, few data are available on frequency of those events. We used miniature video-cameras at nests of grassland passerines and documented partial or complete destruction of eggs or nestlings by cowbirds at 7 of 132 nests monitored with cameras. At least three of the seven cases appeared to be attempts to totally destroy the nest contents; those cowbirds did not appear to be motivated by food or an intent to parasitize the nest. Three cases probably were associated with parasitism, but two involved egg removal late in incubation and the third was unusually destructive. Cowbirds were responsible for 24% of egg losses and 5% of nestling losses caused by predators. The importance of cowbirds as an agent of egg and nestling loss undoubtedly varies among sites and years, but it should not be overlooked.
Nest Desertion by Field Sparrows and its Possible Influence on the Evolution of Cowbird Behavior
Authors: Strausberger Bill M. , Burhans Dirk E. 
Published: September 2019

AbstractIn this study, Field Sparrows (Spizella pusilla) deserted 46% of nests, parasitized by Brown-headed Cowbirds (Molothrus ater) and only 1% of unparasitized nests suggesting that desertion functions primarily as an antiparasite defense. Sparrows did not desert nests following various clutch manipulations that are often associated with parasitism, indicating that desertion was not in response to the presence of cowbird eggs. Sparrows often deserted nests following encounters with real or mounted cowbirds, suggesting that nest desertion is a response to adult cowbirds. Sparrows deserted nests only in stages most vulnerable to the effects of parasitism. That finding is consistent with the possibility that desertion is a parasite-specific response. Sparrows arrived at nests earlier in the day at our Illinois site, where parasitism was greater, than in Missouri. Our findings confirm that host vigilance can prevent successful parasitism, and we provide the first direct evidence that encounters with cowbirds may cause hosts to desert nests. Our findings may help explain why cowbirds parasitize nests extremely early in the morning and lay rapidly. We suggest that consideration be given to host response following interactions with adult brood parasites because those interactions may have implications for both the ecology and evolution of both the parasite and host.
Regional Variation in Response of Field Sparrows to the Threat of Brown-headed Cowbird Parasitism
Authors: Burhans Dirk E. , Strausberger Bill M. , Carey Michael D. 
Published: September 2019

AbstractWe conducted aggression experiments using model cowbirds on nesting Field Sparrows (Spizella pusilla) in heavily, moderately, and rarely parasitized populations. We also documented Field Sparrow morning nest arrival times during the laying period, because Field Sparrows appear to desert nests in response to encounters with laying female cowbirds. Field Sparrows responded most aggressively to cowbird models and arrived the earliest in Illinois, where they were most heavily parasitized. Field Sparrows responded the least to models in Pennsylvania, where they are almost never parasitized. Our results suggest that those host behaviors result from some aspect of host–cowbird interactions, but the extent to which such behaviors are genetic or learned needs further study.
Standard and Comparative Energetics of a Small Avian Herbivore (Phytotoma rara)
Authors: Rezende Enrico L. , López-Calleja M. Victoria , Bozinovic Francisco 
Published: September 2019

AbstractWe studied the standard and comparative energetics of the Rufous-tailed Plancutter (Phytotoma rara), one of the smallest avian herbivores. The Rufous-tailed Plancutter had basal metabolic rate (BMR) values that so far are the highest mass-independent values observed in avian herbivores. Probably the BMR values attained by P. rara reflect its geographic distribution in temperate environments. Using a comparative analysis, we observed that herbivorous birds from temperate geographic areas tend to have higher BMR than tropical ones.
Intraspecific Variation in Commuting Distance of Marbled Murrelets (Brachyramphus marmoratus): Ecological and Energetic Consequences of Nesting Further Inland
Authors: Hull Cindy L. , Kaiser Gary W. , Lougheed Cecilia , Lougheed Lynn , Boyd Sean , Cooke Fred , Danchin E. 
Published: September 2019

AbstractRadio transmitters were deployed on Marbled Murrelets (Brachyramphus marmoratus) at Desolation Sound, British Columbia, Canada, during the 1998 breeding season to assess individual variation in distance birds nested from foraging areas, and potential energetic and ecological consequences of commuting those distances. Radio-tracking from a helicopter was used to locate nests, and tracking from the air and boats was used to locate murrelets on the water. Twenty-three nests were found, with active incubation at 16, and active chick-rearing at 12. A minimum of 3 nests fledged chicks, 9 were failures, and 11 were unknown. Nests were at an elevation of 806 ± 377 m and a distance of 39.2 ± 23.2 km (range 12–102 km) from locations on the water. Birds spent an estimated 1.2 ± 0.7 h per day commuting to and from nests (range 0.3–3.5 h per day). It was estimated that birds expended 3,883 ± 2,296 kJ (range 1,200–10,144 kJ) over the breeding season when commuting to those nests, which was 5–41% of their estimated field metabolic-rate during the breeding season. There was no relationship between distance to nests and breeding success. Either Marbled Murrelets can accommodate that additional energy expenditure, or reduce commuting costs by modifying their foraging behavior. They may forage closer to nest sites when provisioning chicks, thereby reducing commuting costs with a payload, or alter nest visitation rates in relation to distance they nest from foraging areas. Nests further inland may also confer advantages that compensate for the added commuting, or birds might replenish body reserves at the end of the breeding season.
Timing of Mineral Sequestration in Leg Bones of White-tailed Ptarmigan
Authors: Larison James R. , Crock J. G. , Snow Christine M. , Blem C. 
Published: September 2019

Abstract
Birds are unique among vertebrates in that they protect their eggs with rigid, calcium-rich shells. Thus, for a short period of time during the annual reproductive cycle, birds experience extraordinarily high demands for calcium. Two strategies appear to exist for meeting those temporally high demands. Some birds apparently seek out calcium-rich foods immediately prior to and during egg laying whereas others may store calcium in their skeletons over a much longer period of time, mobilizing those reserves only when they are needed for production of eggshells. In this study, we used dual energy, X-ray absorptiometry and inductively coupled plasma mass spectroscopy to monitor annual shifts in bone mineral content in the legs of White-tailed Ptarmigans (Lagopus leucurus). The study organisms were known to live on calcium-poor soils. Despite an apparent shortage of calcium in their diets, the test subjects stored substantial amounts of calcium in their leg bones in months prior to reproduction. Those stores were subsequently depleted during the egg-laying period. We suggest ability to store calcium in the skeleton may afford this species more flexibility in selecting suitable breeding habitats than would be possible otherwise.
Nest-attenders in the Pied Flycatcher (Ficedula hypoleuca) During Nestling Rearing: A Possible Case of Prospective Resource Exploration
Authors: Ottosson Ulf , Bäckman Johan , Smith Henrik G. , Dickinson J. L. 
Published: September 2019

AbstractVisits to nest holes by birds other than their owners is a familiar phenomenon for students of breeding biology. In this study, we evaluate that behavior using a transponder reading system. Eighty-five males and females were fitted with transponders at the end of the incubation period or just after hatching. Nest boxes were fitted with transponder readers from just after hatching until all nestlings fledged. That system revealed 123 visits by birds to nest boxes other than their own, a visit being defined as at least one visit to a separate nest box on a separate day. Males were more often detected at other nests than females (53% of males vs. 29% of females visited) and males on average made more visits than females did (4.8 vs. 2.5 visits). However, both males and females devoted time to visiting other nests while still feeding nestlings. That behavior is more common than previously suspected and is consistent with birds prospecting for future nest sites or investigating patch reproductive success.
Copulatory Behavior of American Avocets and Black-necked Stilts
Authors: Sordahl Tex A. , Murphy M. 
Published: September 2019

Abstract
I recorded details of 231 copulations of American Avocets (Recurvirostra americana) and 39 copulations of Black-necked Stilts (Himantopus mexicanus) in northern Utah. Those data are presented as quantitative descriptions of the copulatory behavior of each species, complementing and clarifying qualitative descriptions in the literature. I observed no qualitative differences between copulatory behavior of avocets and stilts. Small quantitative differences may be related to differences in morphology and habitat preference. Across the family Recurvirostridae, the distinctive copulatory displays of avocets (Recurvirostra spp.) and stilts (Himantopus spp.) seem relatively uniform, but the behavior of the monotypic Banded Stilt (Cladorhynchus leucocephalus) of Australia appears to differ somewhat from typical recurvirostrid copulatory behavior. Attempted copulation with inanimate objects has been reported for at least 6 of the 10 recurvirostrid species.
Large-Scale Variation in Growth of Black Brant Goslings Related to Food Availability
Authors: Sedinger James S. , Herzog Mark P. , Person Brian T. , Kirk Morgan T. , Obritchkewitch Tim , Martin Philip P. , Stickney Alice A. , Bosque C. 
Published: September 2019

AbstractWe examined variation in growth of Black Brant (Branta bernicla nigricans) goslings among two colonies on the Yukon-Kuskokwim Delta in southwestern Alaska and the Colville River Delta on Alaska's Arctic coast. We simultaneously measured abundance and quality of a key food plant, Carex subspathacea, and grazing pressure on that plant at the three colonies. Our goal was to measure variation in gosling growth in relation to variation in grazing pressure and food abundance because growth of goslings is directly linked to first-year survival, and consequently is the principal mechanism for density-dependent population regulation. Goslings grew substantially faster on the arctic coast and were nearly 30% larger than those on the Yukon-Kuskokwim Delta at four to five weeks old. Faster growth on the arctic coast was associated with 2× greater standing crop of C. subspathacea during brood rearing than on the Yukon-Kuskokwim Delta. Dispersal rates are high enough (Lindberg et al. 1998) to rule out local adaptation and genetic variation as explanations for observed variation in growth. Our results are consistent with lower survival of goslings from the Yukon-Kuskokwim Delta during their first fall migration and stronger density-dependent regulation on the Yukon-Kuskokwim Delta than on the Arctic coast.
Reproductive Success of Forest-Dependent Songbirds Near an Agricultural Corridor in South-Central Indiana
Authors: Ford Thomas B. , Winslow Donald E. , Whitehead Donald R. , Koukol Matthew A. , du Plessis M. 
Published: September 2019

AbstractPotential source populations of forest-breeding Neotropical migrant birds may be threatened by anthropogenic changes that increase brood parasitism by Brown-headed Cowbirds (Molothrus ater) and nest predation in heavily forested breeding areas. In south-central Indiana, corridors of agriculture and rural development, ranging from <50 m to several thousand meters in width, penetrate interior portions of the heavily forested landscape. These corridors provide habitat for cowbirds and nest predators. We monitored breeding success of six species of Neotropical migrants and one resident species near an agricultural corridor and in interior forest. We found that nest survival was lower near the agricultural corridor for most of the species in the nestling stage, but no consistent difference in nest survival was detected during the egg stage. Levels of cowbird parasitism were generally elevated near the agricultural corridor. Estimates of the number of fledglings per nesting attempt indicated that seasonal productivity was lower near the agricultural corridor for six of the seven species. Status of populations of birds in south-central Indiana as sources in the Midwest may be compromised by extensive intrusion of agricultural corridors within the contiguous, heavily forested landscape.