bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal Movements and Pelagic Habitat Use of Murres and Puffins Determined by Satellite Telemetry
Authors: Hatch Scott A. , Meyers Paul M. , Mulcahy Danial M. , Douglas David C.
Published: September 2019

We tracked the movements of Common Murres (Uria aalge), Thick-billed Murres (U. lomvia), and Tufted Puffins (Fratercula cirrhata) using surgically implanted satellite transmitters. From 1994–1996, we tagged 53 birds from two colonies in the Gulf of Alaska (Middleton Island and Barren Islands) and two colonies in the Chukchi Sea (Cape Thompson and Cape Lisburne). Murres and puffins ranged 100 km or farther from all colonies in summer, but most instrumented birds had abandoned breeding attempts and their movements likely differed from those of actively breeding birds. However, murres whose movements in the breeding period suggested they still had chicks to feed foraged repeatedly at distances of 50–80 km from the Chukchi colonies in 1995. We detected no differences in the foraging patterns of males and females during the breeding season, nor between Thick-billed and Common Murres from mixed colonies. Upon chick departure from the northern colonies, male murres—some believed to be tending their flightless young—drifted with prevailing currents toward Siberia, whereas most females flew directly south toward the Bering Sea. Murres from Cape Thompson and Cape Lisburne shared a common wintering area in the southeastern Bering Sea in 1995, and birds from Cape Lisburne returned to the same area in the winter of 1996. We conclude that differences in foraging conditions during summer rather than differential mortality rates in winter account for contrasting population trends previously documented in those two colonies.
Survival Rates of Cassin's and Rhinoceros Auklets at Triangle Island, British Columbia
Authors: Bertram Douglas F. , Jones Ian L. , Cooch Evan G. , Knechtel Hugh A. , Cooke Fred
Published: September 2019

We estimated survival of Cassin's Auklet (Ptychoramphus aleuticus) and Rhinoceros Auklet (Cerorhinca monocerata) from recapture rates during 1994–1997. For both species, a two “age”-class model provided the best fit. Estimates of local adult survival were significantly lower for Cassin's Auklet (0.672 ± 0.047) than for Rhinoceros Auklet (0.829 ± 0.095). Our estimate of survival appears lower than that required for the maintenance of a stable population of Cassin's Auklets. The available information indicates that a low survival rate and a declining population at Triangle Island are plausible, particularly given the recent large scale oceanographic changes which have occurred in the North Pacific Ocean. Nevertheless, additional mark-recapture data and indexes of population size are required to rigorously demonstrate population declines at the world's largest Cassin's Auklet colony.
Body Temperature and Resting Behavior of Greater Snow Goose Goslings in the High Arctic
Authors: Fortin Daniel , Gauthier Gilles , Larochelle Jacques
Published: September 2019

We examined the control of body temperature during active and resting behaviors in chicks of a large precocial bird, the Greater Snow Goose (Chen caerulescens atlantica), growing in a cold Arctic environment. Imprinted goslings from 4 to 31 days old maintained their mean (± SD) body core temperature within a narrow range around 40.6 ± 0.2°C (range: 38.7–42.2°C), independently of changes in their thermal environment. Average body temperature increased <0.4°C between 4 and 31 days of age. Hypothermia, potentially an energy-saving mechanism, was not used by active goslings. The potential for heat loss to the environment influenced the length of resting bouts in wild goslings. As environmental temperature increased, wild goslings remained sitting alone for longer periods, whereas when it decreased, brooding behavior was prolonged. The time spent huddling increased with the number of goslings involved. Body temperature during huddling bouts measured in imprinted chicks was significantly lower than during periods of activity, showing a rapid decrease averaging 0.8°C at the onset of huddling, followed by a slow recovery before activity was resumed. Thus, huddling behavior was not used as a rewarming mechanism. Greater Snow Goose goslings appear to prioritize metabolic activity by maintaining a high body temperature, despite the high energy costs that may be involved. Social thermoregulation is used to reduce the energy costs entailed by the strict maintenance of homeothermy.
Taxonomic Affinities of Audubon's Shearwater from Europa Island
Authors: Le Corre Matthieu
Published: September 2019

The western Indian Ocean holds five subspecies of the pantropical Audubon's Shearwater (Puffinus lherminieri), but none was known to breed in the Mozambique Channel. Here, I describe a newly discovered population of Audubon's Shearwaters on Europa Island, southern Mozambique Channel. Comparison of geographic variation of morphometric characters showed that the birds of this population belong to the P. l. bailloni subspecies, previously thought to be endemic to the Mascarenes Islands. They were distinct from the three subspecies of the Comoro, Aldabra, and Seychelles group, suggesting that few successful exchanges of individuals occur between north of the Mozambique Channel and Europa Island. This biogeographic pattern is similar to that of two phylogenetically independent pelagic species from Europa Island. This suggests that a common cause related to geographic isolation and oceanic conditions in the Mozambique Channel may explain the apparent isolation of these three seabird populations from Europa Island.
Difficulties Storing and Preserving Tyrant Flycatcher Blood Samples used for Genetic Analyses
Authors: Conrad Kelvin F. , Robertson R. J. , Boag P. T.
Published: September 2019

We stored blood samples of Eastern Phoebes (Sayornis phoebe) in a lysis buffer (“QLB”) that has been used successfully to preserve blood samples of many other species. We found that although samples from adults were not affected greatly, samples of nestling blood stored for more than a few days did not reliably produce the quantity and quality of DNA useful for multi-locus DNA fingerprinting. We also were unable to extract usable DNA from blood samples collected from Eastern Kingbird (Tyrannus tyrannus) nestlings, but obtained usable DNA from blood of Least Flycatcher (Empidonax minimus) nestlings stored for more than a year. We recommend that anyone planning DNA research with tyrant flycatchers should conduct their DNA extractions as soon as possible after collection. A pilot study to test methods of storage, preservation, and extraction may be necessary before beginning a large-scale project.
Winter Androgen Levels and Wattle Size in Male Common Pheasants
Authors: Papeschi Anna , Briganti Federica , DessÌ-Fulgheri Francesco
Published: September 2019

We report the results of morphological and hormonal measurements of 101 male Common Pheasants (Phasianus colchicus) captured during winter and at the beginning of the breeding season in order to identify correlates of ornament size. Androgen levels in January were bimodally distributed with one group with low hormone levels and a second group with high levels. In February, log transformed androgen levels were normally distributed, with all males showing values similar to the high-level group in January. Wattle size was positively correlated with androgens in January but not in February, suggesting that this male trait can indicate the ability of quality males to start earlier androgen production.
Following of Brown Capuchin Monkeys by White Hawks in French Guiana
Authors: Zhang Shuyi , Wang Lixin
Published: September 2019

One group of brown capuchin monkeys (Cebus apella) was observed for 19 months in French Guiana. White Hawks (Leucopternis albicollis) were seen in association with these monkeys throughout the year. Our study revealed that: (1) hawks mainly followed capuchins in open forest types, and in this vegetation they mainly flew at the height of 10–20 m from the ground where horizontal visibility is better than in other strata of the forest, (2) hawks usually landed preceding the monkey troop spreading into an area, and they followed the capuchin troop when the monkeys were traveling, and (3) no predation of any capuchins by hawks occurred at any time during our study, and seven times it was observed that hawks captured arboreal snakes disturbed by the movement of capuchins. We propose that White Hawks followed brown capuchins in this Amazonian forest primarily for capturing arboreal snakes disturbed by monkey troop movements.
Breeding Biology of Gray-Crowned Tyrannulet in the Monte Desert, Argentina
Authors: Mezquida Eduardo T. , Marone Luis
Published: September 2019

We present information from 75 nests of Gray-crowned Tyrannulet (Serpophaga griseiceps) found in open Prosopis woodlands of the central Monte desert between 1995 and 1997 and compare it with information corresponding to other species of the genus. Breeding occurred from October to January. Nests are small open cups. Both parents participated in nest building, which lasted 4–7 days. In the Prosopis woodland, 98% of the nests were built in chañar (Geoffroea decorticans), which also is commonly used as a nest plant by S. subcristata in east-central Argentina. Mean clutch size did not vary among years nor within the breeding season, and it was similar to that observed in other Serpophaga. Both male and female shared the 13–15 day incubation period. Hatching was asynchronous. Nestling period lasted 13–14 days, during which both parents reared the chicks. Nesting success (26%) appeared to be less than that previously reported for Nearctic open-nesters (50–60%), and Neotropical open-nesters in dry (50%) and wet tropics (35%). Egg and nestling predation were the main cause of nest failure.
Rufous Hummingbird Sucrose Preference: Precision of Selection Varies with Concentration
Authors: Blem Charles R. , Blem Leann B. , Felix Joel , van Gelder Jennifer
Published: September 2019

We tested concentration preferences of Rufous Hummingbirds (Selasphorus rufus) offered sucrose solutions in small feeders in the field. When sucrose solutions differing in increments of 10%, from 10% to 70%, were presented simultaneously, hummingbirds preferred 50% to higher and lower concentrations. They did not show a significant preference in the range from 50% to 70% . When options were offered in pairs of choices differing from 1–25%, hummingbirds demonstrated statistically significant preferences that varied with mean concentration in a curvilinear manner. At concentrations approximating those of hummingbird-pollinated flowers (20%), hummingbirds showed greatest specificity and could distinguish solutions differing by only 1%. At concentrations above and below 20%, greater differences between choices were required to elicit significant preferences.
Endocrine Control of Life-Cycle Stages: A Constraint on Response to the Environment?
Authors: Jacobs Jerry D. , Wingfield John C.
Published: September 2019

Most organisms live in seasonal environments that fluctuate on a predictable schedule and sometimes unpredictably. Individuals must, therefore, adjust so as to maximize their survival and reproductive success over a wide range of environmental conditions. In birds, as in other vertebrates, endocrine secretions regulate morphological, physiological, and behavioral changes in anticipation of future events. The individual thus prepares for predictable fluctuations in its environment by changing life-cycle stages. We have applied finite-state machine theory to define and compare different life-history cycles. The ability of birds to respond to predictable and unpredictable regimes of environmental variation may be constrained by the adaptability of their endocrine control systems. We have applied several theoretical approaches to natural history data of birds to compare the complexity of life cycles, the degree of plasticity of timing of stages within the cycle, and to determine whether endocrine control mechanisms influence the way birds respond to their environments. The interactions of environmental cues on the timing of life-history stages are not uniform in all populations. Taking the reproductive life-history stage as an example, arctic birds that have short breeding seasons in severe environments appear to use one reliable environmental cue to time reproduction and they ignore other factors. Birds having longer breeding seasons exhibit greater plasticity of onset and termination and appear to integrate several environmental cues. Theoretical approaches may allow us to predict how individuals respond to their environment at the proximate level and, conversely, predict how constraints imposed by endocrine control systems may limit the complexity of life cycles.
Vocal Signals of the Village Weaver: A Spectrographic Key and the Communication Code
Authors: Collias Nicholas E.
Published: September 2019

Vocal signals of a species are social signals and guides to its social life. Sound spectrograms were made of 21 of the 26 vocal signals in the extensive vocal repertoire of the African Village Weaver (Ploceus cucullatus). A spectrographic key to vocal signals helps make these signals comparable for different investigators. Short-distance contact calls are given in favorable situations and are generally characterized by low amplitude and great brevity of notes. Alarm cries are longer, louder, and often strident calls with much energy at high frequencies, whereas threat notes, also relatively long and harsh, emphasize lower frequencies. Each male displays his newest nest in a colony with an individually distinctive call to unmated females. The most harmonic calls of the species include a loud call by a male when an unmated female first enters his nest, and also very soft, brief notes given by parent birds to attract a fledgling. Males use somewhat different songs to defend territory, for courtship, and for advertisement. Application of Darwin's (1872) principle of antithesis suggests that vocal signals are composed of basic elements that vary in duration, frequency, loudness, and tonality of notes. These variations can be arranged in pairs of opposite extremes serving to reduce ambiguity in signals, in effect a communication code. At the same time, other selection pressures can enter in according to circumstances to modify the expression of this basic code in evolution.
Local and Regional Effects of Pedestrians on Forest Birds in a Fragmented Landscape
Authors: Fernández-Juricic Esteban
Published: September 2019

I assessed the effects of pedestrians on the distribution of forest bird species in wooded parks in the city of Madrid within and between fragments. Within fragments, increasing levels of pedestrians reduced species richness and overall abundance of individuals within circular plots. The abundance of foraging individuals of four species (Magpies Pica pica, Blackbirds Turdus merula, Starlings Sturnus unicolor, and Woodpigeon Columba palumbus) diminished when pedestrians walked near sampling plots, as well as their breeding densities in relation to increasing disturbance levels. Between fragments, after controlling for fragment size effects, pedestrian rate was negatively related to species richness in two breeding seasons. Species turnover was positively associated to mean pedestrian rate and inter-annual variability in pedestrian rate. At the species level, pedestrian rate negatively affected the probabilities of fragment occupation of 16 species beyond the effects of fragment size and isolation. Locally, the short-term behavioral responses to visitors may reduce the suitability of highly disturbed parks in such a way as to decrease breeding densities and the probabilities of fragment occupation and persistence. The effects of human disturbance in fragmented landscapes should be incorporated into management decisions as another relevant factor that may reduce habitat quality.
Influence of Treefall Gaps on Distributions of Breeding Birds Within Interior Old-Growth Stands in Białowieża Forest, Poland
Authors: Fuller Robert J.
Published: September 2019

Breeding birds were counted using point counts at 50 treefall gaps and 50 closed-canopy sites within one of the largest tracts of old-growth forest in Europe. Numbers of species and individuals were slightly, but significantly, higher at gaps. Overall bird species composition differed substantially at gaps and non-gaps. Dunnock (Prunella modularis), Blackcap (Sylvia atricapilla), and Chiffchaff (Phylloscopus collybita) were significantly more abundant at gaps. Wood Warbler (Phylloscopus sibilatrix) and Red-breasted Flycatcher (Ficedula parva) were significantly more abundant at non-gaps. Warblers (Sylviidae), ground insectivores, ground nesters, and short-distance migrants were significantly more abundant at gaps, but no species groups were more abundant at non-gaps. Eight species breeding in forest edges and young plantations in eastern Poland were not recorded in natural treefall gaps. The proportion of tropical migrant passerines was considerably higher in closed-canopy stands (0.47) than at gaps (0.29), which contrasts with the situation in most managed European forests where the highest proportions of tropical migrants typically occur in young-growth forests.
Sleep-Vigilance Trade-Off in Gadwall During the Winter Period
Authors: Gauthier-Clerc Michel , Tamisier Alain , Cézilly Frank
Published: September 2019

We studied vigilance while sleeping in wintering Gadwalls (Anas strepera) in the Camargue (southern France) during the 1992–1993 and 1994–1995 winters. Vigilance while sleeping was reduced at the beginning and at the end of the winter. During mid-winter, birds in sleeping posture showed the highest level of vigilance, with longer peeks and shorter interpeek intervals. There was no effect of sex on the intensity of vigilant sleep, nor on changes in the pattern of vigilant sleep across the winter period. We discuss the results in relation to the behavioral ecology and energetic constraints of wintering Gadwalls in the Camargue. We suggest that the variation in sleep, measured by eye-closure, and vigilance, measured by eye-opening, in relation to winter period is a result of a trade-off between two opposite requirements: to save energy by sleeping and to monitor the environment by being vigilant.
Correlates of Reproductive Success in Cooperatively Breeding Western American Crows: If Helpers Help, It's Not by Much
Authors: Caffrey Carolee
Published: September 2019

I measured annual reproductive success for a resident population of cooperatively breeding Western American Crows (Corvus brachyrhynchos hesperis) over 6 years, and examined the relationship between it and several ecological and social variables. Most nests (57%) failed to fledge any young, due largely to predation. Success in fledging young was associated with three interrelated variables: (1) the presence of helpers, (2) early nesting, and (3) consistent differences between pairs. Assisted pairs began incubation earlier, some pairs consistently nested early, and the proportion of years that pairs were successful was related to the proportion of years in which they had help. Although both help and incubation date were related to nesting success independent of each other, the effect of help became nonsignificant after controlling for differences between pairs. The slight increase in fledging success possibly attributable to helpers may have been the result of consistently successful pairs succeeding, with help, in otherwise poor years. Postfledging survival was related in part to the size of individuals; larger nestlings tended to have a greater chance of fledging, and once fledged, to have a greater chance of surviving the following 2-week period. Larger nestlings survived to one year of age significantly more often than smaller nestlings.
Badge Size and Extra-Pair Fertilizations in the House Sparrow
Authors: Whitekiller R. R. , Westneat David F. , Schwagmeyer P. L. , Mock Douglas W.
Published: September 2019

For House Sparrows, Passer domesticus, it has been proposed that the size of a male's throat badge correlates with his success in avoiding cuckoldry as well as obtaining extra-pair copulations (EPCs), and that females gain indirect (genetic) benefits from EPCs with large-badged males. Alternatively, female House Sparrows may engage in EPCs as a guard against their social mate's infertility. We used multi-locus DNA fingerprinting to examine paternity and found that among 41 broods and 136 offspring, 20% of the offspring were attributable to extra-pair fertilizations (EPFs). Forty-one percent of the 34 males were cuckolded; however, large-badged males were as likely to be cuckolded as small-badged males. Moreover, we found no evidence that large-badged males were inherently superior to small-badged males in terms of survivorship. We compared the prevalence of unhatched eggs in broods with and without extra-pair offspring to determine whether EPFs are associated with hatching failure. Although we detected no association between hatch failure and EPFs, enhanced fertility remains a plausible EPC benefit to females, but experimental approaches may be required to evaluate its significance.
Copulation Behavior in the Osprey in Relation to Breeding Density
Authors: WidÉn Per , Richardson Malena
Published: September 2019

We studied Osprey (Pandion haliaetus) copulation behavior in two geographically separated subpopulations with different breeding densities. In the low density area, the nearest neighbor distance between nests was 7 km, and in the high density area 1.4 km. The frequency of successful copulations was significantly higher in the high density area, 0.65 hr−1 as compared to 0.30 hr−1. Extra-pair copulations were recorded only in the high density area, and extra-pair visits by intruding Ospreys also were more frequent there. There was no relation between copulations and delivery of food or nest material. Our results support the idea that copulation behavior is related to breeding density, but whether or not this is a result of sperm competition or some other social factor remains undetermined.
Survival and Song-Type Sharing in a Sedentary Subspecies of the Song Sparrow
Authors: Wilson Pamela L. , Towner Mary C. , Vehrencamp Sandra L.
Published: September 2019

The extent and spatial pattern of song-type sharing among neighboring males in one subspecies of Song Sparrow, Melospiza melodia cooperi, were examined in two San Diego County populations. Repertoire size averaged 9.6 song types per male (range 7 to 14). Song-type sharing was greatest between neighbors and declined with distance between territories. Adjacent neighbors shared an average of 22% of their song types. Variation in the amount of sharing between adjacent territory owners was high, ranging from 0% to 86% repertoire overlap. Results are consistent with the expected pattern produced by age-restricted learners that attempt to establish territories near tutors. The probability of a male surviving and remaining on his territory through the breeding and nonbreeding season increased as the fraction of song types shared with adjacent neighbors increased. The amount of song-type sharing may therefore be an indicator of a male's competitive ability to obtain a preferred territory near his tutors, or it may determine a male's effectiveness in using shared and unshared song types to communicate aggressive intentions.
Nest Site Selection and Productivity of Suburban Red-Shouldered Hawks in Southern Ohio
Authors: Dykstra Cheryl R. , Hays Jeffrey L. , Daniel F. Bernard , Simon Melinda M.
Published: September 2019

We measured nest site selection and productivity of suburban-nesting Red-shouldered Hawks (Buteo lineatus) in southwestern Ohio and rural-nesting Red-shouldered Hawks in south-central Ohio. At both the suburban and the rural locations, nest sites had greater canopy height and overall tree basal area than paired random plots, and were located closer to water than were paired random plots. Nest trees also had greater diameter and height than random plot-center trees. Reproductive rates at suburban and rural sites were similar, averaging 2.6–3.1 nestlings per successful nest. Results indicated that suburban-nesting Red-shouldered Hawks were very similar to rural-nesting hawks in both nest site selection and productivity, suggesting that Red-shouldered Hawks were habituated to their suburban environs.
The Rufous Cacholote (Furnariidae: Pseudoseisura) is Two Species
Authors: Zimmer Kevin J. , Whittaker Andrew
Published: September 2019

New information on the vocalizations and behavior of populations of the Rufous Cacholote (Pseudoseisura cristata), combined with a morphometric analysis of museum specimens, reveal that it actually consists of two biological species: a form that is restricted to the arid caatinga region of northeastern Brazil (P. cristata), and a wider-ranging form (P. unirufa) that occupies seasonally flooded savannas and deciduous woodlands in northern and eastern Bolivia, northern Paraguay, and southwestern Brazil. Long considered a subspecies of P. cristata, P. unirufa is shown to be morphologically, vocally, and ecologically distinct from allopatrically distributed populations of P. cristata. Reciprocal playback experiments of tape-recorded vocalizations indicate that neither form responds to the other's vocalizations. The two species may also differ in their breeding systems and social structures. P. cristata is shown to be a cooperative breeder, with nonbreeding helpers assisting in territorial defense, nest-building, and care of nestlings. No evidence of cooperative breeding was found in P. unirufa.
Responses of Egg-Laying Pied Flycatchers to Experimental Changes in Clutch Size: A Re-Examination
Authors: Kern M. D. , Cowie R. J. , Slater F. M.
Published: September 2019

Previous studies with small numbers of clutches suggested that Pied Flycatchers (Ficedula hypoleuca) were determinate egg-layers whose clutch size was fixed before laying began. We found that females lay additional eggs of normal size if clutch size is experimentally reduced, but do not lay fewer eggs when clutch size is increased. In the terms of Kennedy and Power (1990), Pied Flycatchers are removal-indeterminate and addition-determinate.
Egg Recognition in Yellow-Billed and Black-Billed Magpies in the Absence of Interspecific Parasitism: Implications for Parasite-Host Coevolution
Authors: Bolen Ginger M. , Rothstein Stephen I. , Trost Charles H.
Published: September 2019

Yellow-billed Magpies (Pica nuttalli) ejected 100% of nonmimetic eggs placed in their nests despite such behavior having no detectable present day benefits. They are not currently parasitized, nor is there any evidence of a recently extinct brood parasite. Furthermore, there was no molecular evidence of conspecific parasitism, and Yellow-billed Magpies accepted eight of nine conspecific eggs transferred between nests, so recognition would rarely be of benefit if conspecific parasitism occurred. Thus, we suggest that egg recognition in Yellow-billed Magpies is a plesiomorphic trait, a primitive character inherited from a remote ancestor, its nearest relative, the Black-billed Magpie (Pica pica). The latter suffers from parasitism by Great Spotted Cuckoos (Clamator glandarius) in Eurasia and displays rejection behavior throughout Europe in populations that are allopatric and sympatric with this cuckoo. As would be expected if Yellow-billed Magpies inherited rejection behavior from the Black-billed Magpie, or the common ancestor of both species, we found that North American Black-billed Magpies also have well developed egg recognition despite being unaffected by interspecific parasitism. The long-term retention of host defenses as is indicated by magpies has major implications for the coevolutionary interactions between brood parasites and their hosts.
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

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

We 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

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

We 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

We 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

We 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

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

We 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

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

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

Rufous 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

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

I 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

Some 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.