bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sex and Nest Stage Differences in the Circadian Foraging Behaviors of Nesting Burrowing Owls
Authors: Poulin Ray G. , Todd L. Danielle 
Published: September 2019

AbstractAbstractWe used infrared cameras to accurately record the circadian provisioning behaviors of nesting Burrowing Owls (Athene cunicularia) in southern Saskatchewan, Canada. We monitored 19 nests over three years and recorded 4675 prey deliveries. We found a sex-based difference in foraging behavior: males hunted vertebrates during crepuscular periods, and females hunted insects during diurnal periods. Males delivered between 82% and 96% of all vertebrate prey depending on the stage of the nest. Males delivered at least 90% of all insects during early nest stages, after which females delivered an average of 76% of the insects. The rate of vertebrate deliveries increased from 1.3 to 7.7 per 24 hr as the summer progressed, and the number of insect deliveries increased from less than 1 to 18.6 per 24 hr. Vertebrates comprised 98%–99% of prey biomass delivered until females began delivering insects, but even then vertebrates still comprised 94% of prey biomass. Insects were consistently delivered at the highest rate during the day and vertebrates were consistently delivered at the highest rates during the dusk and dawn periods.
The Prelaying Interval of Emperor Geese on the Yukon-Kuskokwim Delta, Alaska
Authors: Hupp Jerry W. , Schmutz Joel A. , Ely Craig R. 
Published: September 2019

AbstractAbstractWe marked 136 female Emperor Geese(Chencanagica) in western Alaskawith VHF or satellite (PTT) transmittersfrom 1999 to 2003 to monitor their spring arrivaland nest initiation dates on the Yukon Delta, andto estimate prelaying interval lengths once at thenesting area. Ninety-two females with functionaltransmitters returned to the Yukon Delta in thespring after they were marked, and we located thenests of 35 of these individuals. Prelayingintervals were influenced by when snow melted inthe spring and individual arrival dates on theYukon Delta. The median prelaying interval was15 days (range  = 12–19 days) in a year when snowmelted relatively late, and 11 days(range  = 4–16 days) in two warmer yearswhen snow melted earlier. In years when snow meltedearlier, prelaying intervals of <12 daysfor 11 of 15 females suggested they initiated rapidfollicle development on spring staging areas. Theprelaying interval declined by approximately0.4 days and nest initiation date increasedapproximately 0.5 days for each day a femaledelayed her arrival. Thus, females that arrivedfirst on the Yukon Delta had prelaying intervals upto four days longer, yet they nested up to fivedays earlier, than females that arrived last. Theproximity of spring staging areas on the AlaskaPeninsula to nesting areas on the Yukon Delta mayenable Emperor Geese to alter timing of follicledevelopment depending on annual conditions, and toinvest nutrients acquired from both areas in eggsduring their formation. Plasticity in timing offollicle development is likely advantageous in avariable environment where melting of snow cover inthe spring can vary by 2–3 weeksannually.
Postovulatory Follicles in Mallards: Implications for Estimates of Breeding Propensity
Authors: Lindstrom Eric B. , Eichholz Michael W. , Eadie John M. 
Published: September 2019

AbstractAbstractWe evaluated the use of postovulatory follicles (POFs) up to 90 days postlaying to determine breeding propensity and clutch size in Mallards (Anas platyrhynchos). During 2002–2003, we examined ovaries from 48 postbreeding female Mallards (24 captive, wild-strain and 24 radio-marked, free-ranging) with known laying histories at periods ranging from 30 to 90 days postlaying. We found that POFs remained identifiable macroscopically (at 4.6–16× magnification) in all females (24 of 24) collected 30–60 days postlaying and in 79% (19 of 24) of females collected 61–90 days postlaying. Using microscopic examination (20–80× magnification), we found that ≥1 POFs remained identifiable in all cross-sectioned ovaries collected from females up to 90 days postlaying. We found a weak correlation between macroscopic POF counts and observed clutch size for females collected 30–60 days postlaying, but not for females collected 61–90 days postlaying. Blind tests using ovaries from known nonbreeding females confirmed that experienced, independent observers correctly distinguished breeding from nonbreeding females 100% of the time up to 60 days postlaying using macroscopic techniques and up to 90 days postlaying using microscopic techniques. These findings indicate that POFs provide a viable method to estimate breeding propensity in free-ranging Mallard populations and potentially other waterfowl species.
Obtaining Offspring Genetic Material: A New Method for Species With High Nest Predation Rates
Authors: Tori Wendy P. , Ryder Thomas B. , Durães Renata , Hidalgo José R. , Loiselle Bette A. , Blake John G. 
Published: September 2019

AbstractAbstractOver the past decade, the field of moleculargenetics has revolutionized our understanding ofavian mating systems, by demonstrating that socialbonds might not accurately reflect parentagebecause of unknown levels of cryptic mating(e.g., extra-pair copulations). Use ofmolecular genetics tools for paternity analysisrequires genetic material from putative parents andnestlings. Unfortunately, high nest predation ratesoften preclude detailed genetic studies of tropicaltaxa. Here, we describe a nondestructive methodthat increases the efficiency of obtaining geneticmaterial from offspring for a group of tropicalpasserines (Pipridae). The method entailsreplacing eggs with plaster replicas, incubatingeggs artificially, and returning hatchlings totheir original nests for further development. Thismethod greatly improved our ability to sampleoffspring, as we collected genetic material from100% of manipulated nests, compared to52% of unmanipulated nests.
Red-Headed Woodpecker Nest-Site Selection and Reproduction in Mixed Ponderosa Pine and Aspen Woodland Following Fire
Authors: Vierling Kerri , Lentile Leigh 
Published: September 2019

Abstract

Abstract
Red-headed Woodpecker (Melanerpeserythrocephalus) populationsare declining at a continental scale, yet little isknown about their nest-site selection and reproductionwithin burned forests. We measured reproductiveparameters and nest-site characteristics at 17Red-headed Woodpecker nests and 17 random sitesbetween 2001 and 2004 in the Black Hills, SouthDakota. The average date the first egg was laid was 17June, and the average clutch size was 5.4 ±0.4. The daily nest survival rate averaged 0.98(overall nest success  = 47%), and predation was the major cause ofnest failure. Red-headed Woodpecker nests occurredfarther from grassland edges in large diameter snagswithin severely burned quaking aspen(Populustremuloides) stands.High-severity fire within these aspen stands resultedin a combination of snag and understorycharacteristics that differed from the surroundingpine forest matrix. Interactions between cover typeand burn severity may have important ecologicalconsequences for Red-headed Woodpeckers in a mixedconifer forest.
An Experimental Test of Snake Skin Use to Deter Nest Predation
Authors: Medlin Elizabeth C. , Risch Thomas S. 
Published: September 2019

AbstractAbstractSome bird species utilize snake skins as nesting material, possibly to decrease predation. We constructed 60 artificial nests simulating the nests of Great Crested Flycatchers (Myiarchus crinitus) in nest boxes to test the prediction that snake skins deter nest predators. Twenty of the boxes lacked rat snake (Elaphe obsoleta) skins (control), 20 had a single skin in the nest, and 20 had a skin in the nest and another displayed outside the box. Five of the control boxes were depredated (20%), while none of the experimental boxes were depredated. Our results supported our prediction that use of snake skins would deter mammalian predators, particularly the southern flying squirrel (Glaucomys volans). Although our results suggest a potential adaptive explanation for this behavior, our design did not allow us to address the degree of olfactory or visual detection by the squirrels, and left other potential explanations untested.
Extra-Pair Fertilizations in Sandhill Cranes Revealed Using Microsatellite DNA Markers
Authors: Hayes Matthew A. , Britten Hugh B. , Barzen Jeb A. 
Published: September 2019

AbstractAbstractThe presence of extra-pair fertilizations (EPF) in a dense breeding population of Sandhill Cranes (Grus canadensis) was examined using six microsatellite DNA markers. In this long-lived species that maintains long-term pair bonds, 4.4%–11% of 45 chicks were not genetically related to one social parent, and extra-pair chicks were present in 5.6%–22% of 18 family groups. Two confirmed extra-pair chicks were from different broods of the same pair that was socially bonded for a minimum of 12 years. The social male was rejected as the genetic father of both of these chicks. Three other potential cases of EPF (two cases in which the social male was rejected as the genetic parent, one in which the social female was rejected) could also have resulted from mate replacement prior to sampling. The range of EPF in this population of Sandhill Cranes is similar to that of other species with similar mating systems. In the confirmed cases of EPF, the female was able to increase her individual reproductive success without losing her territory.
Shorebird Abundance and Distribution on the Coastal Plain of the Arctic National Wildlife Refuge
Authors: Brown Stephen , Bart Jonathan , Lanctot Richard B , Johnson James A , Kendall Steve , Payer David , Johnson Jay 
Published: September 2019

Abstract

Abstract
The coastal plain of the Arctic National Wildlife Refuge hosts seven species of migratory shorebirds listed as highly imperiled or high priority by the U.S. Shorebird Conservation Plan and five species listed as Birds of Conservation Concern by the U.S. Fish and Wildlife Service. During the first comprehensive shorebird survey of the 674 000 ha “1002 Area” on the coastal plain, we recorded 14 species of breeding shorebirds at 197 rapidly surveyed plots during June 2002 and 2004. We also estimated detection ratios with a double counting technique, using data collected at 37 intensively studied plots located on the North Slope of Alaska and northern Canada. We stratified the study area by major habitat types, including wetlands, moist areas, uplands, and riparian areas, using previously classified Landsat imagery. We developed population estimates with confidence limits by species, and estimated the total number of shorebirds in the study area to be 230 000 (95% CI: 104 000–363 000), which exceeds the biological criterion for classification as both a Western Hemisphere Shorebird Reserve Network Site of International Importance (100 000 birds) and a Ramsar Wetland of International Importance (20 000 birds), even when conservatively estimated. Species richness and the density of many species were highest in wetland or riparian habitats, which are clustered along the coast.
Is Selectively Harvested Forest an Ecological Trap for Olive-Sided Flycatchers?
Authors: Robertson Bruce A. , Hutto Richard L. 
Published: September 2019

AbstractAbstractDisturbance-dependent species are assumed to benefit from forestry practices that mimic the appearance of postdisturbance landscapes. However, human activities that closely mimic the appearance but not the fundamental quality of natural habitats could attract animals to settle whether or not these habitats are suitable for their survival or reproduction. We examined habitat selection behavior and nest success of Olive-sided Flycatchers (Contopus cooperi) in a naturally occurring burned forest and an anthropogenically created habitat type—selectively harvested forest. Olive-sided Flycatcher density and nestling provisioning rates were greater in the selectively harvested landscape, whereas estimated nest success in selectively harvested forest was roughly half that found in naturally burned forest. Reduced nest success was probably a result of the relatively high abundance of nest predators found in the artificially disturbed forest. These results are consistent with the hypothesis that selectively harvested forest can act as an “ecological trap” by attracting Olive-sided Flycatchers to a relatively poor-quality habitat type. This highlights the importance of considering animal behavior in biodiversity conservation.
Sexual Size Dimorphism and Morphological Evidence Supporting the Recognition of two Subspecies in the Galápagos Dove
Authors: Santiago-Alarcon Diego , Parker Patricia G. 
Published: September 2019

Abstract

Abstract
Sexual size dimorphism is a conspicuous trait of many wild bird species. Differences in body size between the sexes might reflect selective pressures and trade-offs to optimize performance. Here, we analyze the size dimorphism of the Galápagos Dove (Zenaida galapagoensis) using principal component and discriminant analyses with samples obtained from six islands: Santiago, Santa Fe, Santa Cruz, Española, Genovesa, and Wolf. We also reanalyze published morphological data but also including additional samples from Wolf Island to account for morphological differences among islands. Males were significantly larger than females. Discriminant analyses correctly classified 98% of males and 100% of females, and cross-validation of the model correctly classified 97% of males and 98% of females. We created two sexual size dimorphism indices using wing chord and tarsus as body-size surrogates. Significant differences were found in the sexual size dimorphism index for both measurements among islands. Significant differences in sexual size dimorphism among islands might indicate the role of different selective pressures acting on individual islands (e.g., competition, predation, resources, sexual selection), which might result in life history variation of the species among islands. For the first time, we provide significant morphological evidence supporting the classification of the Galápagos Dove into two subspecies: Z. g. galapagoensis and Z. g. exsul.
Effects of Nest Habitat, Food, and Parental Behavior on Shorebird Nest Success
Authors: Allen Smith Paul , Grant Gilchrist H , Smith James N.M 
Published: September 2019

AbstractAbstractIn environments such as arctic tundra, where bird densities are low and habitats are comparatively homogeneous, suitable nest sites likely are not limited. Under these conditions, reproductive success of birds may be determined by factors other than the habitat characteristics of nest sites. We studied the relative influence of nest habitat, food, nest distribution, and parental behavior on the reproductive success of tundra-breeding shorebirds at East Bay, Southampton Island, Nunavut, Canada. From 2000 to 2002, we monitored the nests of five species: Black-bellied Plover (Pluvialis squatarola), Semipalmated Plover (Charadrius semipalmatus), Ruddy Turnstone (Arenaria interpres), White-rumped Sandpiper (Calidris fuscicollis), and Red Phalarope (Phalaropus fulicarius). For each species, habitat differed between nest sites and random sites. In contrast, habitat differed between successful and failed nest sites only for White-rumped Sandpipers. Shorebirds did not prefer to nest in habitats where food was most abundant. Although nest success varied among species in all years, artificial nest experiments suggested that interspecific variation in predation rate was not related to habitat type. Instead, the marked interspecific variation in nest success may have been related to incubation behavior. Species taking fewer incubation recesses had higher nest success, although these results should be viewed as preliminary. The factor with the greatest interannual influence on nest success was fluctuating predation pressure, apparently related to the abundance of predators and lemmings.
Survival of Band-Tailed Manakins
Authors: Pearce-Higgins James W. , Brace Robin C. , Hornbuckle Jon 
Published: September 2019

Abstract

Abstract
We modeled annual apparent survival of Band-tailed Manakins (Pipra fasciicauda) inhabiting a contiguous forest site and a 10.9 ha forest fragment in lowland Bolivia based on six years of capture-recapture data. There was significant age-related variation in apparent survival, but adult survival rates did not differ significantly with sex. Apparent survival rates of immature birds differed between the two locations, while adult survival rates did not. The most parsimonious model therefore estimated annual survival at 10% for immature birds in the contiguous forest site, 53% for immature birds in the forest fragment, 46% for adults in the first year after initial capture and 68% for adults in subsequent years. Forest fragmentation may have reduced immature dispersal, leading to inflated apparent survival rates in the forest fragment.
Impact of Hurricane Isabel on Bald Eagle Nests and Reproductive Performance in the Lower Chesapeake Bay
Authors: Watts Bryan D. , Byrd Mitchell A. 
Published: September 2019

Abstract

Abstract
We evaluated the impact of Hurricane Isabel on nest loss and reproductive performance of Bald Eagles (Haliaeetus leucocephalus) in the lower Chesapeake Bay. Approximately 40% of Bald Eagle nest trees (n  =  527) were damaged and 127 nests were lost during the storm. Nest loss was significantly higher than in years prior to and after the storm. Only 46% of pairs that lost nests attempted to breed the following season, compared to 85% of pairs that did not lose nests. Of the pairs that made breeding attempts, only 69% of pairs that lost nests during the hurricane produced young compared to 83% of pairs that did not lose nests. Average brood size was also reduced for pairs that lost nests. The disparity in reproductive performance between the two groups narrowed in the second breeding season after the storm. Hurricane Isabel had a significant but short-lived impact on the Bald Eagle breeding population in the lower Chesapeake Bay.
Assessing the Development of Shorebird Eggs Using the Flotation Method: Species-Specific and Generalized Regression Models
Authors: Liebezeit Joseph R , Smith Paul A , Lanctot Richard B , Schekkerman Hans , Tulp Ingrid , Kendall Steve J , Tracy Diane M , Rodrigues Robert J , Meltofte Hans , Robinson Julie A , Gratto-Trevor Cheri , Mccaffery Brian J , Morse Julie , Zack Steve W 
Published: September 2019

Abstract

Abstract
We modeled the relationship between egg flotation and age of a developing embryo for 24 species of shorebirds. For 21 species, we used regression analyses to estimate hatching date by modeling egg angle and float height, measured as continuous variables, against embryo age. For eggs early in incubation, we used linear regression analyses to predict hatching date from logit-transformed egg angles only. For late incubation, we used multiple regression analyses to predict hatching date from both egg angles and float heights. In 30 of 36 cases, these equations estimated hatching date to within four days of the true hatching date for each species. After controlling for incubation duration and egg size, flotation patterns did not differ between shorebirds grouped by mass (≥100 g or <100 g) or taxonomy (Scolopacidae versus Charadriidae). Flotation progressed more rapidly in species in which both adults incubate the clutch versus species in which only one adult incubates the clutch, although this did not affect prediction accuracy. We also pooled all continuous data and created a generalized regression equation that can be applied to all shorebird species. For the remaining three species, we estimated hatching date using five float categories. Estimates of hatching date using categorical data were, overall, less accurate than those generated using continuous data (by 3%–5% of a given incubation period). Our equations were less accurate than results reported in similar studies; data collected by multiple observers and at multiple sites, as well as low sample sizes for some species, likely increased measurement error. To minimize flotation method prediction error, we recommend sampling in early incubation, collecting both egg angle and float height data in late incubation, and developing site- and species-specific regression models where possible.
Effect of Diet Composition on Plasma Metabolite Profiles in a Migratory Songbird
Authors: Smith Susan B , McWILLIAMS Scott R , Guglielmo Christopher G 
Published: September 2019

AbstractAbstractPlasma metabolites provide information about the physiological state and fuel use of birds, and have been used for predicting refueling rates of birds during migratory stopovers. However, little is known about the effect of diet on metabolite concentrations in small songbirds. We investigated the effect of dietary macronutrient composition on lipid and protein metabolites in captive White-throated Sparrows (Zonotrichia albicollis). Birds fed a high-protein, low-carbohydrate insect diet had lower plasma triglyceride concentrations and higher plasma B-hydroxybutyrate concentrations than birds fed a high-carbohydrate, low-protein grain diet during feeding. The insect-fed birds also had higher plasma uric acid concentrations than grain-fed birds and birds fed a low-protein, high-fat, and high-carbohydrate fruit diet. Diet did not significantly influence plasma concentrations of glycerol or nonesterified fatty acids. After subsequent overnight fasting, birds in all three diet groups had similar concentrations of lipid metabolites, but uric acid was marginally elevated in insect-fed birds. Given that dietary macronutrient composition affected certain plasma metabolite concentrations in sparrows, investigators should consider such diet effects when using these metabolites to estimate refueling rates of free-living migratory songbirds, particularly in species that exhibit dietary plasticity during migration.
Cutaneous Water Loss and Lipids of the Stratum Corneum in Dusky Antbirds, a Lowland Tropical Bird
Authors: Muñoz-Garcia Agustí , Williams Joseph B 
Published: September 2019

AbstractAbstractThe stratum corneum, the outer layer of the epidermis, consists of flattened cells embedded in a matrix of lipids, primarily cholesterol, free fatty acids, ceramides, and cerebrosides. The stratum corneum forms a barrier to water vapor diffusion through the skin. In birds, the skin limits excessive water loss at thermoneutral temperatures, but also serves as a vehicle for thermoregulation during episodes of heat stress. We measured total evaporative water loss, cutaneous water loss, and lipids in the stratum corneum in Dusky Antbirds (Cercomacra tyrannina), the first such measurements ever made for birds living in tropical rain forests. We predicted that these birds would have high rates of cutaneous water loss because of their need to thermoregulate rather than to conserve water. We found that Dusky Antbirds lose twice as much water through their skin as birds from temperate environments. We also hypothesized that the proportion of cerebrosides in the stratum corneum would increase relative to that of ceramides if Dusky Antbirds use their skin as a thermoregulatory organ. However, we found that Dusky Antbirds did not show different proportions of ceramides and cerebrosides in the stratum corneum than other species of birds. We also found that Dusky Antbirds had low amounts of free fatty acids in their stratum corneum. Overall, our data support the idea that the interactions of the lipids in the stratum corneum may play an important role in determining rates of water vapor diffusion through the skin.