bluuebunny/crossref_metadata_2025_split huggingface dataset:
Philopatry to Stopover Site and Body Condition of Transient Reed Warblers During Autumn Migration Through Israel
Authors: Merom Kobi , Yom-Tov Yoram , McClery Robin 
Published: September 2019

Abstract
Philopatry to stopover site and changes in body condition of migrating Reed Warblers Acrocephalus scirpaceus were studied in Bet Shean Valley, Israel, where warblers were netted throughout the year. Although the majority of birds were seen only once, the proportion of transients seen twice or more in different years is comparable to the figure for summer residents returning between years, indicating a high degree of philopatry among transients. Transients get heavier with longer duration of stay, up to about 15 days, after which body mass increase appears to level off at about 3 g. Change in body condition, taken to be body mass divided by wing length, also was noted, albeit of less significance. The mean date of arrival in the autumn of birds in their first year was about 20 days later than that of older birds. Reed Warblers use their time effectively to replenish their body mass and improve their condition before starting the dangerous crossing of the Sahara Desert.
Effects of Electromagnetic Fields on the Growth of Nestling American Kestrels
Authors: Fernie Kimberly J. , Bird David M. 
Published: September 2019

AbstractWe studied nestling American Kestrels (Falco sparverius) in a laboratory setting to determine whether exposure to electromagnetic fields (EMFs) affected their growth. Captive nestlings were raised by their parents under control or EMF conditions similar to those occurring near transmission lines in the wild. Nestlings also were exposed to EMFs as embryos when incubated by their parents. Measurements of body mass, and lengths of tarsi, antebrachia, and feathers were taken every three days after hatching. EMF exposure affected the growth of female and male nestlings. EMF nestlings and fledglings were heavier and had longer tarsi. The periods of maximal weight gain and antebrachial growth were delayed in EMF males compared to controls, although EMF males were heavier and had similarly long antebrachia to controls by 21 days of age. Growth of ninth primaries and central rectrices of nestlings were unaffected by EMF exposure. Growth patterns of male and female kestrel nestlings were similar to those previously reported for this species, although the periods of maximal weight gain and bone growth did not occur earlier in EMF males than females as it did in controls.
The Role of Gastrolites on Feeding Behavior and Digestive Efficiency in the Rufous-Collared Sparrow
Authors: Victoria LÓpez-Calleja M. , Soto-Gamboa Mauricio , Rezende Enrico L. 
Published: September 2019

Abstract
We examined grit consumption in the facultative granivorous Rufous-collared Sparrow (Zonotrichia capensis). Grit consumption fluctuated seasonally and was significantly correlated with morphological changes in the digestive tract, and with seed size. The highest values of grit consumption and digestive tract mass were observed during winter. Laboratory experiments suggested that grit consumption was a voluntary behavior rather than the result of accidental ingestion, and favored digestibility. Grit consumption varied considerably when Z. capensis fed on different types of food, but remained constant when food availability varied. We suggest that grit consumption together with morphological changes in the digestive tract allow Z. capensis to increase energy acquisition in response to higher energy demands during wintertime.
Does Beak Size Affect Acoustic Frequencies in Woodcreepers?
Authors: Palacios Maria G. , Tubaro Pablo L. 
Published: September 2019

AbstractWe assessed the effect of beak morphology on the acoustic structure of woodcreeper (subfamily Dendrocolaptinae) songs using a comparative analysis of independent contrasts. For the song of each species, we measured the maximum and minimum frequencies, the bandwidth, and the emphasized frequency. Residuals of variation in beak length and acoustic frequencies after controlling for body size and phylogeny were calculated for each species and compared. We found a negative relationship between the residuals of acoustic frequencies and the residuals of beak length. This relationship was significant for emphasized frequency when we excluded two open-habitat species, Scimitar-billed Woodcreeper (Drymornis bridgesii) and Narrow-billed Woodcreeper (Lepidocolaptes angustirostris). This result is consistent with the hypothesis that the suprasyringeal vocal tract has resonating properties that affect the frequency spectrum of the song.
Numerical and Functional Responses of Migrant Bald Eagles Exploiting a Seasonally Concentrated Food Source
Authors: Restani Marco , Harmata Alan R. , Madden Elizabeth M. 
Published: September 2019

AbstractWe determined the numerical and functional responses of migrant Bald Eagles (Haliaeetus leucocephalus) feeding on spawning kokanee salmon (Oncorhynchus nerka) at Hauser Reservoir, Montana from 1991–1995. Number of Bald Eagles was positively correlated with the fluctuating number of salmon carcasses during four of five years. Immigration and emigration rates were similar across years and were facilitated by several behavioral and physical characteristics of eagles: group foraging, communal roosting, and keen eyesight. Number of subadult eagles showed closer synchrony with density of salmon carcasses than did adult eagles. Eagles scavenging for salmon exhibited a Type II functional response. Handling times of scavenging eagles remained constant across the range of salmon carcass densities, whereas daily attack rates increased. Functional responses of scavenging eagles differed between age groups; adults exhibited a Type I response, whereas that of subadults could not be characterized. Handling times of scavenging adults were constant, but those of subadults increased with salmon density. Attack rates of scavenging adults increased with salmon carcass density. Consumption rates differed between age groups and among eagles using foraging modes of scavenging, stooping, and pirating, which suggests that eagles viewed live and dead salmon as alternative prey types. Bald Eagle scavenging of kokanee salmon was inversely density dependent.
Water Balance During Real and Simulated Long-Distance Migratory Flight in the Bar-Tailed Godwit
Authors: Landys Mėta M. , Piersma Theunis , Visser G. Henk , Jukema Joop , Wijker Arnold 
Published: September 2019

AbstractWe examined Bar-tailed Godwits (Limosa lapponica), a long-distance migratory shorebird, for evidence of dehydration toward the end of their 4,300-km migratory flight from West Africa to the Dutch Wadden Sea. Bar-tailed Godwits are ideal subjects for research on flight range constraints because they can readily be caught in migratory flight. Because godwits are capable of long nonstop travel, we hypothesized that they are physiologically adapted to minimize en route water loss, and therefore, do not experience water imbalance under standard migratory conditions. To test this hypothesis, we compared the hydration state of flying Bar-tailed Godwits at the end of a long bout of migratory flight to that of recently-landed godwits. Flying godwits were hydrated to the same degree as birds with free access to water, suggesting that godwits maintain water balance during migratory flight. To corroborate these empirical results, we ran a theoretical simulation of flight-incurred loss of water and energy in a male Bar-tailed Godwit based on the published model by Klaassen et al. (1999). When a low body drag is assumed, model output suggests that Bar-tailed Godwits flying at altitudes ranging from sea level to 3,000 m will avoid dehydration, and that flight at about 3,000 m will result in the longest possible flight range.
Comparative Seasonal Fecundity of Four Neotropical Migrants in Middle Appalachia
Authors: Dececco Jennifer A. , Marshall Matthew R. , Williams Alan B. , Gale George A. , Cooper Robert J. 
Published: September 2019

Abstract
We estimated daily rates of nest predation and Brown-headed Cowbird (Molothrus ater) parasitism as well as nesting success for the Red-eyed Vireo (Vireo olivaceus), Blue-headed Vireo (V. solitarius alticola), Wood Thrush (Hylocichla mustelina), and Worm-eating Warbler (Helmitheros vermivorus) at two study sites in the middle Appalachian mountains from 1995–1998. These daily rates were then used in combination with species-specific life history parameters to estimate seasonal fecundity. Although daily predation rates were similar across species and sites, parasitism rates and nesting success differed within species between sites and among species within a site. The vireos generally experienced the highest rates of parasitism and subsequently the lowest estimates of seasonal fecundity. However, differences in parasitism and nesting success were not always an accurate predictor of seasonal fecundity. Despite significantly different estimates of nesting success, the Red-eyed Vireo and Blue-headed Vireo had similar estimates of seasonal fecundity. In contrast, estimates of nesting success for the Worm-eating Warbler and Wood Thrush were similar yet there were differences in seasonal fecundity. Life history attributes such as season length, ability to produce additional broods, and ability to raise a host young with a cowbird young were important in determining seasonal fecundity among species. We show the importance of including multiple species within a study framework and illustrate how predation and parasitism differentially affect these species with respect to seasonal fecundity.
Winter Flocking of Insectivorous Birds in Montane Pine-Oak Forests in Middle America
Authors: King David I. , Rappole John H. 
Published: September 2019

AbstractWe studied mixed-species insectivorous bird flocks in pine-oak forests in Middle America during three winter seasons to determine whether patterns of flock structure and dynamics were similar to those reported from other tropical sites. We also analyzed patterns of association among bird species, as well as their foraging behavior and the vegetation characteristics associated with birds in flocks. We encountered 333 flocks containing 144 species, of which 26 species had adequate sample sizes for analyses. The size and rate of movement of the flocks were similar to those reported from other Neotropical sites, however, the species richness of our flocks was lower than reported in most other studies, perhaps due to simpler vegetation structure or higher latitude. Only 3 of 50 significant correlations between species pairs were negative, indicating that species generally were not restricted in their participation in mixed-species flocks by other species. In only one instance did we observe correspondence between the association of species-pairs in flocks and their foraging behavior. For most species there was no relationship between association between species-pairs in flocks and vegetation parameters with which they were associated. Thus, additional factors besides foraging facilitation and mutual association with particular vegetation characteristics must be responsible for many of the positive correlations among species pairs. We suggest that non-random association among species within flocks may result in part from enhanced vigilance for predator detection afforded by flock members using similar parts of the environment at the same time.
Effects of Ectoparasites on Nestling Body Mass in the House Sparrow
Authors: Weddle Carie B. 
Published: September 2019

Abstract
House Sparrow (Passer domesticus) nestlings were screened for ectoparasites; the most common ectoparasite was Pellonyssus reedi, a haematophagous mite. Parasite load was used to determine whether: ectoparasites have an effect on chick body mass prior to fledging, relative chick body mass is a within-brood predictor of relative parasite load, and parasite load per brood correlates with brood size. There was a negative correlation between parasite load and chick body mass, indicating that ectoparasites can reduce the quality of host offspring. Within broods, a chick's body mass was not related to its parasite load relative to its siblings' loads, suggesting that these ectoparasites do not preferentially target particular nestlings based on size. No relationship was found between brood size and total parasite load; thus, there was no evidence that within-nests, mite population size is limited by brood size.
RAPD-PCR Amplification of DNA Extracted from Avian Blood Infected With Haemoproteus Fails to Produce False Positive Markers
Authors: Zwartjes Patrick W. , Hnida John A. 
Published: September 2019

Abstract
We tested whether contamination of avian blood by the parasite Haemoproteus could cause the amplification of false positive genetic markers generated by random amplified polymorphic DNA (RAPD). DNA was extracted from blood taken from five Rock Doves (Columba livia) infected with Haemoproteus, and one uninfected control individual. A drug treatment was administered to clear the infection, and a second DNA sample extracted. The parasitized and unparasitized DNA samples were used in RAPD reactions with 20 different 10-nucleotide primers, which produced 178 well-resolved markers. In no case were any of the reaction products specific to the parasitized samples, and in almost all cases the products were found consistently across all replications of infected and non-infected samples. The high ratio of avian to parasite DNA and the greater genome complexity of the host probably prevents the amplification of markers unique to parasite species such as Haemoproteus.
Relationship Between Tail Color Pattern and Reproductive Success, Mate Acquisition and Nest Predation in Rufous Bush Chats
Authors: Alvarez Fernando 
Published: September 2019

AbstractRufous Bush Chats (Cercotrichas galactotes) show a conspicuous tail color pattern consisting of terminal white and subterminal black patches which are shown in tail display during nest defense, aggression, and courtship. Multiple linear regression of visual tail features of males showed that in the two years of study, birds with higher bilateral symmetry in the black patches attained higher seasonal reproductive success, mated earlier in the season, and their nests were less likely to be depredated. In one year, birds with greater white terminal patches also attained higher reproductive success and their nests were less likely to be depredated, and in the other year birds with longer tails paired earlier. I suggest that these tail features have an effect on reproductive success by facilitating early pairing and/or by diminishing nest predation.
Nine Years After the Exxon Valdez Oil Spill: Effects on Marine Bird Populations in Prince William Sound, Alaska
Authors: Irons David B. , Kendall Steven J. , Erickson Wallace P. , McDonald Lyman L. , Lance Brian K. 
Published: September 2019

Abstract
We compared post Exxon Valdez oil-spill densities of marine birds in Prince William Sound from 1989–1991, 1993, 1996, and 1998 to pre-spill densities from 1984–1985. Post-spill densities of several species of marine birds were lower than expected in the oiled area of Prince William Sound when compared to densities in the unoiled area. These negative effects continued through 1998 for five taxa: cormorants, goldeneyes, mergansers, Pigeon Guillemot (Cepphus columba), and murres. Black Oystercatchers (Haematopus bachmani) and Harlequin Ducks (Histrionicus histrionicus) exhibited negative effects in 1990 and 1991. Loons showed a weak negative effect in 1993. Black-legged Kittiwakes (Rissa tridactyla) showed relative decreases in 1989, 1996, and 1998 which may have been caused by shifts in foraging distribution rather than declines in populations. Glaucous-winged Gulls (Larus glaucescens) showed positive effects in most post-spill years. Murrelets and terns showed relative increases in 1993, 1996, and 1998. Generally, taxa that dive for their food were negatively affected, whereas taxa that feed at the surface were not. Effects for some taxa were dependent upon the spatial scale at which they were analyzed. Movements of birds and the mosaic pattern of oiling reduced our ability to detect oil-spill effects, therefore our results may be conservative. Several marine bird species were negatively affected at the population level and have not recovered to pre-spill levels nine years after the oil spill. The reason for lack of recovery may be related to persistent oil remaining in the environment and reduced forage fish abundance.
Allozymic Genetic Structure and Natural Habitat Fragmentation: Data for Five Species of Amazonian Forest Birds
Authors: Bates John M. 
Published: September 2019

AbstractI studied allozymic variation in five species of Amazonian birds at two geographic scales. At a local scale (all sites within 200 km of one another), I included samples from six sites, three within continuous forest and three in natural forest fragments thought to be several thousand years old. I examined both genetic variation and differentiation to determine whether there were genetic effects related to forest fragmentation. At this local scale, I found little evidence in the allozymic data that clearly suggested genetic structure had been affected in any uniform pattern among species. However, there was genetic differentiation at this level and estimated gene flow (Nmest from private alleles) was low relative to what is reported in other avian studies. At the regional level, I compared samples from sites that were 500–1,500 km from one another from two Amazonian areas of endemism (Inambari and Rondônia). Four of the five species exhibited substantial differentiation between samples from the two areas of endemism, consistent with other studies of genetic differentiation in Neotropical forest understory birds.
Antbird Guilds in the Lowland Caribbean Rainforest of Southeast Nicaragua
Authors: Cody Martin L. 
Published: September 2019

AbstractSome 20 species of antbirds occur in lowland Caribbean rainforest in southeast Nicaragua where they form five distinct guilds on the basis of habitat preferences, foraging ecology, and foraging behavior. Three guilds are habitat-based, in Edge, Forest, and Gaps within forest; two are behaviorally distinct, with species of army ant followers and those foraging within mixed-species flocks. The guilds each contain 3–6 antbird species. Within guilds, species are segregated by body size differences between member species, and in several guilds are evenly spaced on a logarithmic scale of body mass. Among guilds, the factors by which adjacent body sizes differ vary between 1.25 and 1.75. Body size differences may be related to differences in preferred prey sizes, but are influenced also by the density of the vegetation in which each species customarily forages.Resumen. Unas 20 especies de aves hormigueras viven en el bosque tropical perennifolio, sureste de Nicaragua, donde se forman cinquo gremios distinctos estribando en preferencias de habitat, ecologia y comportamiento de las costumbres de alimentacion. Las diferencias entre las varias especies son cuantificadas por caractaristicas del ambiente vegetal y por la ecologia y comportamiento de la alimentación, y usados para definir cinco grupos o gremios (“guilds”). Tres gremios se designan por las relaciones de habitat: edge (margen), forest (selva), y gaps (aberturas adentro la selva); dos mas por comportamiento, partidarios de army ants (hormigas armadas) y mixed-species flocks (forrejando en bandadas de especies mexcladas). Estos gremios contenien 3–6 especies hormiguera. Dentro de grupos hay diferencias regulares en peso de cuerpo entre las especies; diferencias que igualmente existen entre los gremios diferentes, con razónes medios de 1.25 a 1.75 en peso de cuerpo. Las diferencias en el tamaño de especies individuales probablemente estan relaciónadas con las diferencias entre los tamaños de las presas preferidas, pero quizas son influenciadas por la densidad de la vegetacion en donde se alimentan.
Characteristics of Foraging Habitats and Chick Food Provisioning by Tropical Roseate Terns
Authors: Ramos Jaime A. 
Published: September 2019

Abstract
I studied tropical Roseate Terns (Sterna dougallii) on Aride Island, Seychelles, between 1997–1999. Productivity in 1998 was 0.58 fledglings/breeding pair, and in 1999 no young fledged. Roseate Terns on Aride concentrated their foraging along the coastline exposed to prevailing winds, with flock size over this area being significantly correlated with amount of food offered to chicks. In 1998, Lesser Noddies (Anous tenuirostris) were present in 91% of the Roseate Tern flocks, but in 1999 occurred in only 32%. During the 1998 successful breeding season, Roseate Terns were associated with dense flocks of Lesser Noddies over predatory fish, whereas during the 1999 failure season most Roseate Tern flocks were either monospecific or mixed with Fairy Terns (Gygis alba), and without predatory fish. The mean flock size of Roseate Terns (82 vs. 6 birds) and the rate of foraging attempts (8.3 vs. 2.8 attempts min−1) were significantly greater in association with predatory fish. Mullidae (Parupeneus or Mulloidichthys) were the primary prey taken by Roseate Terns, and alternative sources of food were apparently scarce. The high daily variations in the amount of food brought to chicks, intermediate periods of low food delivery, and an apparent seasonal decline in the amount of food brought to the colony suggest that food is unpredictable on a daily and seasonal basis. Absence of predatory fish may explain complete breeding failures and periods of low food delivery, but the importance of other factors is unknown. Information on the ecology and movement patterns of predatory fish around Aride Island is needed to assist the conservation of the Roseate Terns.
Contrasting Strategies of Provisioning and Chick Growth in two Sympatrically Breeding Albatrosses at Campbell Island, New Zealand
Authors: Waugh Susan M. , Weimerskirch Henri , Cherel Yyes , Prince Peter A. 
Published: September 2019

AbstractThe provisioning strategies of two closely related species of albatross breeding sympatrically were studied at Campbell Island, New Zealand. Black-browed Albatrosses (Diomedea melanophrys) had a higher provisioning rate of chicks than Grey-headed Albatrosses (D. chrysostoma) as a result of a higher feeding frequency. Provisioning and satellite-tracking data suggest that Black-browed Albatrosses forage over neritic waters in trips of up to 5 days, in combination with longer trips over oceanic waters. In contrast, it was not possible to separate clearly short and long trips in Grey-headed Albatrosses, but they probably forage mostly over oceanic waters, combined with rafting or feeding near the colony during stays of short duration at sea. No inter-annual differences in foraging trip duration were apparent between years for either species. Chicks were fed larger meals at older ages and when in poorer condition, probably due to a limitation on the rate of assimilation of food. For both species, chick condition after feeding did not influence the duration of foraging trips. Black-browed Albatrosses from Campbell Island feed locally in neritic waters and up to 2,000 km from the colony, in contrast to conspecifics from other sites which feed principally over neritic waters. Grey-headed Albatrosses were largely dependent on oceanic resources as for conspecifics studied elsewhere. This study shows that foraging and provisioning strategies are flexible within species, allowing them to exploit more or less distant resources.