bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Foraging Habitats and Chick Food Provisioning by Tropical Roseate Terns
Authors: Ramos Jaime A.
Published: September 2019

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

The 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.
Reproductive Success of American Kestrels: The Role of Prey Abundance and Weather
Authors: Dawson Russell D. , Bortolotti Gary R.
Published: September 2019

We investigated how natural variation in abundance and availability of the main prey of American Kestrels (Falco sparverius), small mammals, influenced provisioning rates by parents, and offspring size and survival. Provisioning behavior of kestrels was not constrained by the abundance of food in the environment; however, the availability of food, mediated through variation in weather, appeared to significantly influence parental provisioning behavior. Moreover, variation in weather had clear effects on reproductive success because nestlings exposed to inclement weather were smaller and lighter at fledging, and less likely to survive to fledging, compared to nestlings raised during good weather conditions. Prey abundance was not related to offspring size or survival. Our results suggest American Kestrels are limited by the availability, as opposed to abundance, of food on territories. It is likely that during our study, prey abundance was above some minimum threshold necessary to support successful reproduction, and so variation in weather affected reproduction more than variation in prey abundance.
Nesting Habitat and Reproductive Success of Southwestern Riparian Birds
Authors: Powell Brian F. , Steidl Robert J.
Published: September 2019

Vegetation structure and floristic composition strongly influence the structure of bird communities. To assess the influence of vegetation and other environmental characteristics on songbirds, we quantified nest-site characteristics and reproductive success of a riparian songbird community in Arizona. Although we found interspecific variation in characteristics associated with nest sites, we identified two suites of species that chose sites with similar characteristics. These “nest groups” were explained largely by nest height and characteristics of nest trees. Overall, nest success was low for songbirds in this community, and averaged 23%. The most common cause of nest failure was predation (81%), although brood parasitism by Brown-headed Cowbirds (Molothrus ater) was highest at nests of Bell's Vireos (Vireo bellii) (29%). No vegetation or environmental features were associated with the likelihood of cowbird parasitism for any species; nest success for Bell's Vireos was negatively associated with the amount of netleaf hackberry (Celtis reticulata) in the understory. Arizona sycamore (Platanus wrightii) and netleaf hackberry trees contained 41% and 17% of all nests, respectively, and therefore provide critically important nesting substrates for birds in this rare yet diverse vegetation community.
Patterns of Flock Size, Diet, and Vigilance of Naturalized Monk Parakeets in Hyde Park, Chicago
Authors: South Jason M. , Pruett-Jones Stephen
Published: September 2019

We examined patterns of diet, foraging group size, and vigilance effort of naturalized Monk Parakeets (Myiopsitta monachus) in Hyde Park, a neighborhood of Chicago, Illinois. Parakeets exhibited a highly seasonal and varied diet consisting of fruits, seeds, and buds, and they fed almost exclusively on birdseed provided at backyard feeding stations during the winter months. Birds foraged in groups of 1 to 31 birds, but most flocks were of 10 birds or less. Foraging group size was greatest in the fall and early winter, and smallest at the beginning of the spring when breeding began. Monk Parakeets adjusted their vigilance effort with changes in flock size. Individual vigilance effort declined with increasing flock size through a decrease in time spent scanning as well as the number of times scans were initiated. The number of parakeets exhibiting vigilance in a flock at any given time also decreased with flock size. It is likely that the highly adaptable and varied diet of Monk Parakeets contributes greatly to the persistence and growth of populations in a variety of North American habitats.
Mitochondrial DNA and Morphological Variation of White-Winged Doves in Texas
Authors: Pruett Christin L. , Henke Scott E. , Tanksley Susan M. , Small Michael F. , Hogan Kelly M. , Roberson Jay
Published: September 2019

White-winged Doves (Zenaida asiatica) in Texas are separated into four subspecies primarily based on morphological variation. However, problems differentiating the subspecies by morphological measurements alone and a recent range expansion have led to questions about their systematic status and population structure. We evaluated both morphological characters and a 289 base-pair segment of the mitochondrial control region from 183 White-winged Doves taken from 31 locations in Texas, New Mexico, and Arizona. Twenty-seven variable base changes were observed, which resulted in 44 haplotypes. An analysis of haplotypes yielded little phylogenetic signal; however, analyses of haplotype frequencies indicated geographic heterogeneity between doves collected in the four historic subspecies ranges. Doves from the range expansion areas were intermediate in size and genetically homogenous. Morphological analyses suggested congruency between control region variation and body size. Our data support the recognition of two subspecies of White-winged Doves with a zone of intergradation in the range expansion areas. The dispersal of White-winged Doves into the expansion areas appears to be a congruent process by both subspecies.
Definitive Prebasic Molt of Gray Catbirds at two Sites in New England
Authors: Heise Colleen Dwyer , Rimmer Christopher C.
Published: September 2019

We studied the pattern and timing of prebasic molt in adult Gray Catbirds (Dumetella carolinensis) at two New England sites: Block Island, Rhode Island (BIRI), and the Vermont Institute of Natural Science (VINS) in Woodstock, Vermont. Catbirds at VINS initiated molt earlier and molted at a significantly slower rate than catbirds at BIRI. Mean individual molt durations spanned approximately 54 days at VINS and 44 days at BIRI. The two groups ended molt at about the same time. Catbirds at VINS were more variable in the timing of their molt. At both sites, second-year catbirds began and ended molt significantly earlier than after second-year catbirds. Males and females did not differ significantly in their rate or timing of molt at either site. Behavioral observations at BIRI indicated that catbirds spent less time foraging during the heaviest period of molt, but that increased foraging during late molt stages coincided with increases in fat stores, indicating overlap of molt and hyperphagy. We found no evidence that Gray Catbirds at either site departed for migration prior to completing remigial molt. The later molt schedule of BIRI birds likely resulted from the extended breeding season of some individuals. We believe that molt schedules at the two sites were influenced less by latitude per se than by site-specific differences in vegetation, food abundance, and temperature, resulting from differing elevations and conditions of coastal and inland environments.
Cultural Diversification in the Flight Call of the Ringneck Parrot in Western Australia
Authors: Baker Myron C.
Published: September 2019

I investigated geographic variation in a parrot vocalization to obtain an understanding of cultural population differentiation and exchange between hybridizing taxa. The flight calls of Ringneck Parrots (Barnardius zonarius) were tape recorded in Western Australia within and outside the zone of overlap and hybridization between the Port Lincoln (B. z. zonarius) and Twenty-eight (B. z. semitorquatus) subspecies. Measured variables distinguished the Twenty-eight call from those in the overlap populations. Although birds in typical Twenty-eight plumage were present in the overlap zone, no Twenty-eight flight calls were found, suggesting convergence by immigrants. Populations within the hybrid zone also were acoustically differentiated as dialects associated with roosting areas. Observations on the social behavior of the birds indicated that this call functions in coordination of movements of the mated pair. Roost-specific dialects might aid pairs in finding each other in the event of separation during the day's foraging activity.
Comparison of Coastal Fringe and Interior Forests as Reserves for Marbled Murrelets on Vancouver Island
Authors: Burger Alan E. , Bahn Volker , Tillmanns Angeline R. M.
Published: September 2019

Much of the protected habitat available to the threatened Marbled Murrelet Brachyramphus marmoratus and other old-growth associated species in the Pacific Northwest is in narrow strips along the coast (e.g., parks and scenic fringes). Using data over two years from three watersheds on southwest Vancouver Island, we show that such shoreline strip forests represent suboptimal habitat for murrelets. Murrelet detections, including circling and subcanopy behaviors, were significantly lower at 30 coastal stations (20–250 m from the shoreline edge) than at 30 interior stations (1.5–21.0 km inland). Densities of predators were significantly higher at the coastal stations. The coastal trees were of similar mean height and diameter, but they had lower structural diversity and provided fewer and less suitable (thinner epiphyte cover on large boughs) nesting platforms than trees in the interior. When possible, reserves for Marbled Murrelets should be placed in interior and not shoreline forests.
Correlates of Harlequin Duck Densities During Winter In Prince William Sound, Alaska
Authors: Esler Daniel , Bowman Timothy D. , Dean Thomas A. , O'Clair Charles E. , Jewett Stephen C. , McDonald Lyman L.
Published: September 2019

We evaluated relationships of Harlequin Duck (Histrionicus histrionicus) densities to habitat attributes, history of habitat contamination by the 1989 Exxon Valdez oil spill, and prey biomass density and abundance during winters 1995–1997 in Prince William Sound, Alaska. Habitat features that explained variation in duck densities included distance to streams and reefs, degree of exposure to wind and wave action, and dominant substrate type. After accounting for these effects, densities were lower in oiled than unoiled areas, suggesting that population recovery from the oil spill was not complete, due either to lack of recovery from initial oil spill effects or continuing deleterious effects. Prey biomass density and abundance were not strongly related to duck densities after accounting for habitat and area effects. Traits of Harlequin Ducks that reflect their affiliation with naturally predictable winter habitats, such as strong site fidelity and intolerance of increased energy costs, may make their populations particularly vulnerable to chronic oil spill effects and slow to recover from population reductions, which may explain lower densities than expected on oiled areas nearly a decade following the oil spill.
Influence of Female Age and Body Mass on Brood and Duckling Survival, Number of Surviving Ducklings, and Brood Movements in Redheads
Authors: Yerkes Tina
Published: September 2019

I documented brood and duckling survival, the number of surviving ducklings, and brood movements of Redheads, and examined the association between these variables and female age and body mass. Redhead brood success was 55% and duckling daily survival rates averaged 0.868. Female body mass, but not age, was related to brood and duckling survival and the number of surviving ducklings. Successful females were heavier and produced more ducklings. All brood-movement measures differed between successful and unsuccessful females, however, the distance of the first move between wetlands accounted for the most variability in brood success. Increased body mass, but not age, was associated with longer first brood movements.
Effects of Hatching Date and Egg Size on Growth, Recruitment, and Adult Size of Lesser Scaup
Authors: Dawson Russell D. , Clark Robert G.
Published: September 2019

Evidence suggests that birds breeding early in the season or laying larger eggs are at a selective advantage because quality and survival of their offspring are higher. We tested whether wild Lesser Scaup (Aythya affinis) hatching early in the season or from larger eggs had enhanced growth as ducklings and larger size or higher probability of recruiting to the local breeding population in years after hatching. After correcting for age at capture, body mass, head length, and culmen of ducklings were inversely related to hatching date, but were unrelated to egg volume. As adults, late-hatched birds had shorter wing lengths (second-year birds only) and tended to have smaller head lengths (all after-hatch year birds) than early hatching birds. We suggest that later-hatching birds are smaller due to increased competition for food during brood rearing. Recruitment probability increased as natal egg volume increased and decreased among birds with later natal hatching dates. We speculate these results are due to higher mortality of ducklings hatched from small eggs, and because early-hatched birds have more time to acquire nutrient reserves that would reduce vulnerability to costs of migration.
Effects of Water Conditions on Clutch Size, Egg Volume, and Hatchling Mass of Mallards and Gadwalls in the Prairie Pothole Region
Authors: Pietz Pamela J. , Krapu Gary L. , Buhl Deborah A. , Brandt David A.
Published: September 2019

We examined the relationship between local water conditions (measured as the percent of total area of basins covered by water) and clutch size, egg volume, and hatchling mass of Mallards (Anas platyrhynchos) and Gadwalls (A. strepera) on four study sites in the Prairie Pothole Region of North Dakota and Minnesota, 1988–1994. We also examined the relationship between pond density and clutch size of Mallards and Gadwalls, using data collected at another North Dakota site, 1966–1981. For Mallards, we found no relationships to be significant. For Gadwalls, clutch size increased with percent basin area wet and pond density; hatchling mass marginally increased with percent basin area wet. These species differences may reflect, in part, that Mallards acquire lipid reserves used to produce early clutches before they reach the breeding grounds, whereas Gadwalls acquire lipid reserves locally; thus Gadwall clutches are more likely to be influenced by local food resources.
Reproductive Success and Survival in Relation to Experience During the First Two Years in Canada Geese
Authors: Raveling Dennis G. , Sedinger James S. , Johnson Devin S.
Published: September 2019

We studied the relationship between family associations of immature Canada Geese (Branta canadensis) and their reproductive success as 2-year-olds and survival to three years. A higher proportion of immature Canada Geese associated with family members survived to breeding age and were more successful in reproducing in their first potential year of sexual maturity (age 2) than were geese that were not in family associations. These results illustrate the benefits of prolonged parental care outweighing costs to parents and the probable influence of family association on future successful breeding. Many reproductive failures of vertebrates with complex social organization may be related to experience during maturation.
Impact of Brood Parasitism on Nest Survival Parameters and Seasonal Fecundity of Six Songbird Species in Southeastern Old-Field Habitat
Authors: Whitehead Maria A. , Schweitzer Sara H. , Post William
Published: September 2019

We monitored 259 nests of six Brown-headed Cowbird (Molothrus ater) hosts within old-field habitat on James Island, South Carolina during the 1997 and 1998 breeding seasons to determine the effect of parasitism on three nest-survival parameters (clutch size, hatching rate, and number of fledglings). We determined daily predation and parasitism rates, and probability of nest abandonment after parasitism to derive an estimate of seasonal fecundity. Clutch size of parasitized nests was reduced in four host species. Brood parasitism did not affect hatching rate in any species, and reduced the number of fledglings from only Blue Grosbeak (Guiraca caerulea) nests. Despite brood reduction during the nesting cycle, cowbird parasitism had little impact on seasonal fecundity of these host species because of low parasitism intensity, double-brooding behavior, and hosts' ability to raise their own young with cowbird young.
Sociality and Foraging Behavior of the Cerulean Warbler in Venezuelan Shade-Coffee Plantations
Authors: Jones Jason , Perazzi Paolo Ramoni , Carruthers Erin H. , Robertson Raleigh J.
Published: September 2019

We examined the use of Venezuelan shade-coffee plantations by the Cerulean Warbler (Dendroica cerulea) and other Neotropical migrants. Cerulean Warblers were commonly observed as pairs in mixed-species flocks. Average (± SE) flock size was 13 ± 2 species with 22 ± 3 individuals. Average flock territory size was 2.5 ± 0.2 ha. No differences were detected in foraging behavior (maneuvers, location, or success) among adult males, adult females, and immature birds. Adult males were often observed visiting flowers of canopy trees. The results of this study indicate that shade coffee plantations may provide suitable wintering habitat for Cerulean Warblers although comparisons with other habitats are needed.
Comparative Phylogeography of Some Aridland Bird Species
Authors: Zink Robert M. , Kessen Ann E. , Line Theresa V. , Blackwell-Rago Rachelle C.
Published: September 2019

We compared mitochondrial DNA sequences for six species distributed across the aridlands of North America to document phylogeographic patterns and assess levels of congruence. The Curve-billed Thrasher (Toxostoma curvirostre) and Canyon Towhee (Pipilo fuscus) show genetic divisions between the Sonoran and Chihuahuan Deserts, whereas the Cactus Wren (Campylorhynchus brunneicapillus), Black-tailed Gnatcatcher (Polioptila melanura), and Verdin (Auriparus flaviceps) do not. Most likely, species without phylogeographic structure only recently colonized their entire current range. Therefore, although these species are today part of a widespread avifauna, species' distributions were historically different from today. In Baja California, the Cactus Wren and the Verdin show phylogeographic breaks at 28°–30°N, consistent with a division previously described in the LeConte's Thrasher (Toxostoma lecontei) and in some members of the herpetofauna. These genetic divisions were likely caused by isolation resulting from a mid-peninsular seaway that existed one million years ago. Hence, these species appear to have been broadly sympatric for at least one million years. In contrast, the California Gnatcatcher (Polioptila californica) lacks such a phylogeographic division, and apparently only recently expanded into the northern part of its current range. Thus, not all species in Baja California have had similar histories, although further sampling might reveal a general pattern. Comparative phylogeography therefore provides an indirect method of evaluating the long-term stability of faunas via assessment of levels of phylogeographic congruence, and can show whether particular species are likely to have had a long period of co-association.
Using Hydrogen Isotope Geochemistry to Estimate the Natal Latitudes of Immature Cooper's Hawks Migrating Through the Florida Keys
Authors: Meehan Timothy D. , Lott Casey A. , Sharp Zachary D. , Smith Ruth B. , Rosenfield Robert N. , Stewart Andrew C. , Murphy Robert K.
Published: September 2019

We constructed a regression model for the relationship between stable-hydrogen isotope ratios in immature Cooper's Hawk (Accipiter cooperii) feathers (δDf) and precipitation in areas where feathers were grown (δDp) across much of the latitudinal and longitudinal extent of the species' breeding range. We used our model to estimate δDp values from δDf values of immature Cooper's Hawks captured during migration in the Florida Keys. We compared these estimated δDp values to a published map of δDp values of North American precipitation to learn the latitudinal origins of migrants. We reviewed previous migration banding studies to estimate the longitudinal range of migrants. Our analysis suggested that most of the immature Cooper's Hawks migrating through the Keys originated in natal areas in the Mid-Atlantic and Southeast regions of the continent. We found no difference in the passage date of northern and southern birds or in the latitudinal origins of males and females. This new information will aid in the interpretation of population trends generated from the ongoing migration count in the Keys.
Repertoire, Structure, and Individual Distinctiveness of Thick-Billed Murre Calls
Authors: Lefevre Kara , Gaston Anthony J. , Montgomerie Robert
Published: September 2019

We describe the vocal repertoires of Thick-billed Murre (Uria lomvia) adults and chicks during the breeding season. Using recordings from throughout the chick-rearing period, we identified four distinct calls of chicks and six of adults. We present sonograms and quantitative descriptions of each call and summarize the behavioral context in which they were used. Chick calls are mostly flute-like sounds at approximately the same pitch that tend to develop from a simple peep during hatching through a rapidly frequency-modulated departure call, given shortly before, during, and after they leave the colony at fledging. Departure calls appear to facilitate interactions between the chick and the attending male parent during this risky period for the chick. Adult calls are lower pitched and sound more gruff, with different call types having significantly different pitch, duration, and number of syllables. Among-individual variation in the crow calls of adults accounts for 44% of the measured variation in this call and indicates the potential for individual recognition, such as the recognition of parents' calls by their chicks, which we have previously documented. Temporal features may form the basis of recognition of adult calls in this species, given that they accounted for twice as much variation as frequency features among individual adults.
Do Woodpecker Drums Encode Information for Species Recognition?
Authors: Dodenhoff Danielle J. , Stark Robert D. , Johnson Eric V.
Published: September 2019

We investigated whether woodpecker drums are exchanged interspecifically and attempted to ascertain the drum variables responsible for species recognition. Playback experiments were conducted on four woodpecker species (Nuttall's Picoides nuttallii, White-headed P. albolarvatus, Hairy P. villosus, and Downy P. pubescens Woodpeckers) comparing behavioral responses to sympatric hetero- and conspecific drums. There was a significant difference in behavioral responses to sympatric hetero- versus conspecific drums; individuals responded less intensely to drums of heterospecifics when drum cadences were dissimilar. Allopatric species drums with similar cadences were used to examine whether cadence was a variable that encodes species identity. There was no significant difference between responses to allopatric hetero- versus conspecific drums with a similar cadence, indicating that the drum's cadence encodes information for species recognition. Further playbacks eliminated drum duration and spectral properties as important variables for species recognition. Results suggest that if an individual drums at a similar cadence to a sympatric heterospecific, then their signal may elicit a conspecific response.
Male Badge Size Predicts Dominance Against Females in House Sparrows
Authors: Liker András , Barta Zoltán
Published: September 2019

We investigated dominance relationships and the use of male badge size as a status signal in a mixed-sex flock of House Sparrows (Passer domesticus). Specifically, we tested whether females differ from males in their fighting behavior or dominance status, and whether badge size predicts dominance and fighting success of males in male-female fights. We found that both sexes were involved frequently in aggressive encounters, and the mean dominance rank of males did not differ from the mean rank of females. Badge size was the only significant predictor of the dominance rank of males, and was a good predictor of their aggressiveness measured as the proportion of fights initiated. On the other hand, female dominance rank was correlated with body weight. In male-female fights, both the proportion of female-initiated aggressive interactions and the proportion of fights won by females decreased with increasing size of the opponent's badge. Large-badged males dominated more females in dyadic interactions than smaller-badged males. These correlational results suggest that male badge size may be used as a signal of dominance status between male and female House Sparrows in winter flocks.
Extra-Pair Paternity in the Common Murre
Authors: Birkhead Tim R. , Hatchwell Ben J. , Lindner Robert , Blomqvist Donald , Pellatt E. Jayne , Griffiths Richard , Lifjeld Jan T.
Published: September 2019

Multi-locus DNA fingerprinting was used to estimate the frequency of extra-pair paternity in the Common Murre (Uria aalge), a colonial, sexually monomorphic seabird that breeds at very high densities and in which extra-pair copulation is frequent. Common Murres produce a single chick. We detected 6 cases of extra-pair paternity in 77 families (7.8%). This value was higher than the proportion of successful extra-pair copulations (1.6%) estimated from behavioral data from an earlier study of the same population.
Aggressive Nest Intrusions by Male Humboldt Penguins
Authors: Taylor Sabrina S. , Leonard Marty L. , Boness Daryl J.
Published: September 2019

During observations at a breeding colony of Humboldt Penguins (Spheniscus humboldti), we noted five male penguins enter nests occupied by breeding pairs and engage in aggressive interactions with the resident adult. These nest intrusions resulted in egg loss or infanticide, and accounted for 11.1% of breeding failure in the colony. Two intruder males ultimately mated with respective resident females. This behavior had not been observed previously in Humboldt Penguins and we suggest that it may occur when males are unable to obtain mates through advertising at the nest. Intrusion behavior may slow down population recovery in this endangered species.
Female Responses to Intraspecific Brood Parasitism in the Tree Swallow
Authors: Whittingham Linda A. , Dunn Peter O.
Published: September 2019

We studied female responses to experimental intraspecific brood parasitism (IBP), or egg-dumping, in Tree Swallows (Tachycineta bicolor). Unlike other species of swallows, Tree Swallow nests are rarely parasitized by conspecifics. We experimentally parasitized nests of Tree Swallows to investigate how females respond to uncertain maternity. Host females accepted a parasitic egg if it was added to the nest within 3 days of the host's first egg (62%). In contrast, the host female buried the parasitic egg (24%) or deserted the nest (14%) when the parasitic egg was added 4 or more days before the host's first egg. The acceptance of parasitic eggs close to the host's own laying date is similar to the behavior reported for other species; however, egg burial and nest desertion appear to be rare as responses to intraspecific brood parasitism. We suggest that the low level of IBP in Tree Swallows has evolved as an indirect consequence of females defending their nest cavity against usurpation.
Context and Frequency of Infanticide in Communally Breeding Guira Cuckoos
Authors: Macedo Regina H. F. , Cariello Mariana , Muniz Laura
Published: September 2019

We studied the context of brood reduction through infanticide by communally breeding Guira Cuckoos (Guira guira) in central Brazil. During seven reproductive seasons, we monitored 142 nests from egg laying until fledging. Almost all nests (97%) lost eggs through ejection, and chick deaths occurred in 72% of all nests with hatchlings. There was evidence for infanticide in 38% of the nests that exhibited some mortality. We compared egg and chick mortality in the early part of the season with the later part, when insect abundance declines, but found no significant differences. Less than one-third of all nests monitored showed asynchronous hatching of eggs, and in those that did, chick death was not in reverse hatch order. Although there are several plausible explanations for infanticide, we highlight one likely candidate, which is its interpretation as a sexually selected trait where individuals gain reproductive benefits by provoking the group's nesting failure.
Differences in Depredation by Small Predators Limit the Use of Plasticine and Zebra Finch Eggs in Artificial-Nest Studies
Authors: Maier Thomas J. , Degraaf Richard M.
Published: September 2019

Small mammals, such as mice and voles, have been implicated as major egg predators of Neotropical migrant passerines by field studies using soft plasticine eggs or the very small eggs of Zebra Finch (Taeniopygia guttata). Nevertheless, the effort required to depredate these commonly used egg surrogates may be less than that required to depredate the larger, thicker-shelled eggs of most passerine species. To compare the depredation of these surrogates to that of the eggs of a mid-sized passerine by a ubiquitous small predator, we exposed dissimilar pairs of plasticine, Zebra Finch, and House Sparrow (Passer domesticus) eggs to captive white-footed mice (Peromyscus leucopus). Plasticine eggs were marked by mice more than either kind of real egg, and Zebra Finch eggs were breached more often than House Sparrow eggs. We conclude that the use of either plasticine or Zebra Finch eggs may lead to overestimation of the ability or proclivity of small mammals to actually depredate the eggs of most passerines.
Assessing Raptor Diet: Comparing Pellets, Prey Remains, and Observational Data at Hen Harrier Nests
Authors: Redpath Stephen M. , Clarke Roger , Madders Mike , Thirgood Simon J.
Published: September 2019

We compared techniques to assess diet at 17 Hen Harrier (Circus cyaneus) nests. Diet was measured directly from observations and compared to estimates from pellets, prey remains and a combination of pellets and remains. For data pooled across nests, pellets over-represented mammalian prey and under-represented avian prey. Prey remains over-represented large prey and under-represented small prey. Combining pellet and remains data did not eliminate these biases. Pellets gave higher diversity values than direct observations and detected more small prey species. For data analyzed on a nest by nest basis, estimates from pellets were significantly related to estimates from direct observations for three prey types by frequency and all types by biomass. These linear relationships were used to predict frequencies and biomass of prey types in the observed diet at five new nests. Our findings suggest that pellets are useful for estimates of prey diversity and as an index of the frequency of certain prey types in the diet, but direct observations are necessary to help quantify the biases inherent in diet estimates.
Size Characteristics of Stones Ingested by Common Loons
Authors: Franson J. Christian , Hansen Scott P. , Pokras and Mark A. , Miconi Rose
Published: September 2019

Common Loon (Gavia immer) carcasses recovered in New England had more stones of greater combined mass in their stomachs than loons from the southeastern United States. Stones retained in sieves with mesh sizes between 4.75 and 8.00 mm accounted for the greatest percentage (by mass) of grit in loon stomachs. The median longest dimension of the largest single stone in each stomach was 12.5 mm in loons from New England and 10.7 mm in loons from the southeast (maximum = 23.1 mm and 16.8 mm, respectively). A recent national proposal to restrict the use of certain fishing weights in the United States called for a ban on lead fishing sinkers of 25.4 mm or less in any dimension. Our findings suggest it is unlikely that Common Loons would ingest lead fishing weights greater than 25.4 mm in any dimension, if such ingestion was solely the result of their search for replacement stones for their stomachs. However, this does not preclude the possibility that loons may ingest larger fishing weights under other circumstances, such as the consumption of fish with attached sinkers.
Egg Size, Body Size, Locomotion, and Feeding Performance in Captive King Eider Ducklings
Authors: Anderson Vanessa R. , Alisauskas Ray T.
Published: September 2019

We studied the effect of egg volume and body size on swimming speed, endurance, and feeding rate in captive King Eider (Somateria spectabilis) ducklings in the Canadian arctic. Sprint speed, endurance, and feeding rate were positively related to egg size and body size. Large ducklings from large eggs performed better than small ducklings from small eggs. Ducklings that are more capable swimmers and have higher feeding rates may grow more quickly and be more effective at predator evasion. Thus, ducklings from large eggs may have a survival advantage over those from small eggs under conditions where predation and nutrition may constrain survival.
Seasonal Fluctuations of Birds, Fruits, and Flowers in a Subtropical Forest of Argentina
Authors: Malizia Lucio R.
Published: September 2019

I quantified monthly variation in species composition and captures of birds in a premontane forest of northwestern Argentina. Seasonal patterns of frugivore-insectivores and nectarivores were compared with fruit and flower abundances, respectively. The composition of the entire bird community fluctuated seasonally; frugivore-insectivores showed a peak in captures during the wet season, insectivores peaked at the end of the dry season, and nectarivores peaked during the dry season. At a local scale (∼50 ha), captures of frugivore-insectivores were not correlated with number of plant species with ripe fruits for any vegetation stratum considered, but were correlated with a fruit phenology index that considers crop size. At a plot scale (∼7.5 ha), only understory flower abundance and captures of nectarivores were correlated, but only in the plot where both were more abundant. At a net-site scale (50 m2), captures of the Rufous-bellied Thrush (Turdus rufiventris) were correlated with understory fruit abundance, but only in the plot where fruits were more abundant. These results suggest that seasonal fluctuations in birds may be driven to some extent by their food resources. Premontane forest provides habitat for many migrants and also presumably acts as a source of birds that emigrate to disturbed areas. Although premontane forests should be a conservation priority for the region, they are poorly protected and suffering high deforestation.
Reproductive Biology of Sabine's Gull in the Canadian Arctic
Authors: Stenhouse Iain J. , Grant Gilchrist H. , Montevecchi William A.
Published: September 2019

We studied the reproductive biology of Sabine's Gulls (Xema sabini) breeding on Southampton Island, in the eastern Canadian Arctic, from May to August in 1998 and 1999, and compared our results to information collected from the same region in 1980. Breeding phenology was 10 days earlier in 1998 than in these other years, and reflects an earlier onset of snowmelt in that year. Nests were dispersed, with a density of 7.6 to 8.7 nests per km2. Sabine's Gulls exhibited strong interannual fidelity to breeding sites. Mean clutch size was lower in 1999 than 1998, and lower in both these years than in 1980. Hatching success was 63% in 1998, but only 21% in 1999 due to increased predation, most likely by arctic fox (Alopex lagopus). Adult gulls and chicks abandoned nest-sites within a few hours of the hatching of the last chick and relocated to coastal ponds, where adults continued to attend chicks. In comparisons of the reproductive biology of Sabine's Gull to closely related “tern-like” gull species and other “black-headed” gulls, Sabine's Gull showed a number of distinct ecological and behavioral differences and represents an ecological outlier within the Laridae.
Provisioning Rate and Attendance Patterns of Wandering Albatrosses at Bird Island, South Georgia
Authors: Berrow Simon D. , Croxall John P.
Published: September 2019

We investigated foraging behavior of Wandering Albatrosses (Diomedea exulans) breeding at South Georgia to assess how sex and season-specific foraging patterns relate to provisioning performance. We estimated Wandering Albatross chicks require 60–65 kg of food over the chick-rearing period; males deliver 54% of this total. Meal size delivered by both sexes remained essentially constant throughout the post-brooding chick-rearing period, but foraging trip duration varied considerably. Females made consistently longer foraging trips and delivered smaller meals but transported an average load that was 20% heavier in proportion to their body mass than males. We suggest that chick-rearing places greater demands on females compared with males and Wandering Albatrosses work hard to deliver food during the first half of chick rearing (at the expense of their own condition), thereafter reduce their work rate, presumably so as not to compromise their survival.
Food Supply and the Consequences of Egg Size in the Thick-Billed Murre
Authors: Hipfner J. Mark , Gaston Anthony J. , Storey Anne E.
Published: September 2019

We examined the effect of egg size on post-hatching development in the Thick-billed Murre (Uria lomvia), an Arctic seabird that lays a one-egg clutch, at a colony where food availability during chick-rearing was low (Digges Island, Nunavut, Canada). We compared our results to those of a previous study conducted at a colony where food availability was higher (Coats Island, Nunavut). To control for underlying phenotypic correlations between egg size and parental quality, we switched eggs at random among pairs. Egg size positively affected the rate of early wing-feather growth, but contrary to prediction, the advantage enjoyed by chicks from large eggs over those from small eggs at Digges Island (1.6 days' feather growth on average) was no greater than at Coats Island (2.0 days). Egg size had no effect on the rate at which chicks gained mass at Digges Island, but young from large eggs tended to remain heavier than those from small eggs. At Coats Island, this occurred only in a year in which chicks grew relatively slowly, offering some support for the hypothesis that a large egg confers greater advantage when feeding conditions are unfavorable. Adults at Digges Island invested heavily in provisioning their chicks, but there was no evidence of a trade-off between egg size and provisioning. As costs associated with large eggs have not been detected in Thick-billed Murres, the existence of considerable variation in egg size, beyond that associated with female age or experience, remains unexplained.
Phylogenetic Relationships in Bearded Manakins (Pipridae: Manacus) Indicate That Male Plumage Color is a Misleading Taxonomic Marker
Authors: Brumfield Robb T. , Braun Michael J.
Published: September 2019

The piprid genus Manacus is composed of four allospecies that are readily distinguishable by differences in male plumage color. Electrophoretic data for two populations of each of the four forms plus seven outgroup piprid taxa were collected from 32 isozyme loci and used to infer phylogenetic relationships. Each Manacus form was monophyletic, with the exception of M. manacus, in which the trans-Andean (west of the Andes) population was sister to M. vitellinus, rather than to its conspecific cis-Andean (east of the Andes) population. This controversial relationship, supported by the synapomorphic allele PGM-2b as well as allele frequencies at ADA, GOT-1 and LGG, is consistent with general biogeographic patterns in the region, but indicates that male plumage color is an unreliable taxonomic marker. Reconstruction of male plumage color on the tree confirms that gold plumage is a derived state in M. vitellinus, a finding consistent with the possibility that gold plumage is an evolutionary novelty in vitellinus which has spread recently under positive selection. Among piprids, there was strong support for a group composed of Antilophia, Chiroxiphia, and Corapipo, and for a group composed of Pipra mentalis, P. fasciicauda, and Dixiphia pipra. Manacus is more closely related to the P. mentalis + P. fasciicauda + D. pipra group. The isozymes supported Lepidothrix as the basal taxon of those examined.
A Half-Century Comparison of Breeding Birds in the Southern Appalachians
Authors: Haney J. Christopher , Lee David S. , Wilbert Mark
Published: September 2019

We evaluated long-term (∼50-year) change in a bird community of an extensively forested region of the southern Appalachian mountains in North Carolina and Tennessee. A species accumulation curve for a 1996–1998 survey identified a core of 50 breeding species in upper elevations of the Unicoi Mountains. Since a 1944–1946 survey, dominant species have remained identical, no species have disappeared, and mean ranked abundance of both short and long-distance migrants has not changed. Permanent residents, however, had decreased in rank by the late 1990s. Three “new” disturbance-dependent species, American Crow (Corvus brachyrhynchos), Indigo Bunting (Passerina cyanea), and Song Sparrow (Melospiza melodia), expanded into interior forest along a recently constructed parkway. Largest apparent increases in ranked abundance of individual species occurred in eight Neotropical migrants that rely upon mature, forest-interior habitat, whereas largest apparent declines in ranked abundance occurred in land-use generalists, cavity nesters, and three other Neotropical migrants. Modifications to land-use were reasonable explanations for changes in most species. Little change in community structure, greater representation of many Neotropical migrants, and virtual absence of Brown-headed Cowbirds (Molothrus ater) suggest that this large, continuous forest retained and probably regained functional integrity for forest birds during the latter half of the twentieth century.
Species Limits in Antbirds: The Thamnophilus Punctatus Complex Continued
Authors: Isler Morton L. , Isler Phyllis R. , Whitney Bret M. , Walker Barry
Published: September 2019

In a previous study (Isler et al. 1997) we examined species limits in the Thamnophilus punctatus complex of the Neotropics. We recommended that six taxa be considered species, but were unable to make recommendations regarding two morphologically distinct and geographically restricted taxa, leucogaster and huallagae, due to the lack of vocal recordings which were essential to our methodology. Analysis of newly obtained recordings has found that vocal differences support the separation at the species level of leucogaster and huallagae from five of the six species in the complex (T. atrinucha, T. stictocephalus, T. sticturus, T. pelzelni, and T. ambiguus). However, leucogaster and huallagae could not be distinguished vocally from each other nor from nominate punctatus to an extent that supported species status, and they are retained as subspecies under our recommended guidelines (Isler et al. 1998, 1999). The Thamnophilus punctatus complex affords an interesting opportunity for future molecular studies that compare the genetic distances among populations that have differentiated vocally and those that have not. The question of species status of leucogaster and huallagae is pressing because the ranges of both taxa are limited to sub-Andean basins in northwestern Peru and southwestern Ecuador that increasingly are under cultivation.
Geographical Variation in the Calls of the Choughs
Authors: Laiolo Paola , Rolando Antonio , Delestrade Anne , de Sanctis Augusto
Published: September 2019

The calls of 22 populations of the Red-billed Chough (Pyrrhocorax pyrrhocorax) and the Alpine Chough (P. graculus) were sampled throughout the Palearctic region. In both species calls differed in frequencies, either by latitude or longitude in the Red-billed Chough and mostly by longitude in the Alpine Chough. Frequencies varied according to body size, being higher in smaller-bodied populations and lower in larger-bodied ones, as predicted by the inverse relationship between body size and frequency. We hypothesize that, besides the effect of physical constraints determining frequencies, past climatic events and the geomorphological history of the Pleistocene also have influenced the present pattern of diversification. We also hypothesize that gene flow and ‘cultural’ flow have constrained the evolution of clear-cut population differences between European and North African populations, whose segregation could be quite recent.