bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foraging Strategies and Niche Dynamics of Coexisting Shorebirds at Stopover Sites in the Southern Great Plains
Authors: Davis Craig A. , Smith Loren M. 
Published: September 2019

AbstractShorebirds encounter variable and unpredictable food resources at stopover sites during migration through interior North America. We studied foraging strategies and niche dynamics of American Avocets (Recurvirostra americana), Long-billed Dowitchers (Limnodromus scolopaceus), Least Sandpipers (Calidris minutilla), and Western Sandpipers (C. mauri) at stopover sites in 60 playa lakes of the southern Great Plains. Those species were selected because they are common in our study area during migration and represent a wide range of morphological classes. Overall foraging niches (linear combination of diet diversity, prey size, foraging-method diversity, and water depth) of avocets and dowitchers were segregated from each other and from Least and Western sandpipers. Overall foraging niches of Least and Western sandpipers were similar. Examination of single niche dimensions showed that avocets and dowitchers consumed larger prey and foraged in deeper water than did Least and Western sandpipers. Within the range of prey sizes consumed by the four individual species, all species selected small prey (0.1–5.0 mm). Preference of relatively small prey by avocets and dowitchers was likely a function of small prey being more abundant in playas than large prey (>10 mm). However, selection of small prey by Least and Western sandpipers was likely a function of lower handling costs associated with small prey. Abundance of prey items in diets of each species was not correlated with nutritional and energetic quality of prey items, but abundance of prey in the diet was correlated with abundance of prey in playa lakes. That suggests that all four shorebird species adopt an opportunistic foraging strategy during migration. Use of opportunism is likely critical for shorebirds to continue migration and arrive on breeding grounds in good condition.
Estimating Repeatability of Egg Size
Authors: Flint Paul L. , Rockwell Robert F. , Sedinger James S. 
Published: September 2019

AbstractMeasures of repeatability have long been used to assess patterns of variation in egg size within and among females. We compared different analytical approaches for estimating repeatability of egg size of Black Brant. Separate estimates of repeatability for eggs of each clutch size and laying sequence number varied from 0.49 to 0.64. We suggest that using the averaging egg size within clutches results in underestimation of variation within females and thereby overestimates repeatability. We recommend a nested design that partitions egg-size variation within clutches, among clutches within females, and among females. We demonstrate little variation in estimates of repeatability resulting from a nested model controlling for egg laying sequence and a nested model in which we assumed laying sequence was unknown.
Effect of Investigator Disturbance on Nest Attendance and Egg Predation in Eurasian Oystercatchers
Authors: Verboven Nanette , Ens Bruno J. , Dechesne Sharon 
Published: September 2019

AbstractEurasian Oystercatchers (Haematopus ostralegus) breeding on the salt marsh of Schiermonnikoog (Dutch Wadden Sea) lose many eggs to predators, mainly Herring (Larus argentatus) and Mew gulls (L. canus). We estimated that the probability for an egg to survive from laying until hatching was 69%. Daily egg mortality was higher during the laying period than during the incubation period. When researchers were present in the study area, oystercatchers spent more time at greater distances from the nest. We investigated whether human disturbance resulted in more eggs being lost to predators. Two experimental areas were in turn visited at high and at low frequency. From a preliminary analysis, we estimated higher daily egg mortality rates when nests were checked three times per day instead of once every other day. However, high-frequency nest checks provided more information on newly laid and lost eggs, especially during the laying period. After correcting for that extra information (by simply deleting it), the egg mortality rates were no longer different. We conclude that human disturbance did not increase egg loss, rather egg mortality rates were underestimated when nests were checked only once per two days.
Nocturnal Activities of Post-breeding Wood Storks
Authors: Bryan Jr. A. Larry , Snodgrass Joel W. , Robinette John R. , Daly James L. , Brisbin Jr. I. Lehr 
Published: September 2019

Abstract
Postbreeding season activities of Wood Storks (Mycteria americana) were examined during 24 h long observation periods at inland impoundments and a coastal roost site. Storks were present at inland impoundments and foraged more at night there than at other times of the day. Wood Stork attendance at the coastal roost site was significantly reduced during nocturnal low tides than during daytime low tides or at either period of higher tide levels. Presumably, storks were leaving the roost to forage on fish concentrated in tidal creeks by dropping tides. Nocturnal foraging in freshwater and estuarine systems may be an advantageous strategy for the tactile-feeding storks by reducing the likelihood of their being observed by their prey and possibly by reducing competition with other wading birds. Also, some prey species in both freshwater and saltwater environments are more active nocturnally than diurnally, this increasing their likelihood of capture by nocturnal-foraging Wood Storks. In the coastal setting, low tide events (two per ∼24 h) typically provide at least one “pulse” of stork prey in draining tidal creeks during the nocturnal period.
Territorial Movements of Black-throated Blue Warblers in a Landscape Fragmented by Forestry
Authors: Harris Rebecca J. , Reed J. Michael 
Published: September 2019

AbstractMany forest bird species show inhibition to entering open areas, including crossing habitat gaps. We examined the responses of Black-throated Blue Warblers (Dendroica caerulescens) to conspecific song playback within forest, at clearcut-forest ecotones, and across logging roads to assess movements of this Neotropical migrant into open areas. Males responded readily to song playbacks in all areas, and moved significantly farther into clearcuts than they did within intact forest (40.4 ± 2.9 m and 17.1 ± 1.2 m, respectively). Their singing, aggressive trilling, and alarm-calling rates were highest in response to playback from clearcuts, intermediate during road-crossings, and lowest within forest. Males moved farthest into the oldest regenerating clearcuts (>15 years old), indicating that vegetation structure also influences their movement into open areas. Second-year males were more responsive than older males, moving farther to reach speakers in all areas, and showing a nonsignificant trend of moving farther into clearcuts. We found that extensive movements into open areas occur in response to simulated territorial intrusion, indicating that small-scale habitat fragmentation by forestry may not disrupt territorial movements of that species.
Sexual Size Dimorphism and Positive Assortative Mating in Alpine Choughs (Pyrrhocorax graculus)
Authors: Delestrade Anne 
Published: September 2019

AbstractThe degree of sexual size dimorphism in a number of different morphological characters was examined in a social corvid, the Alpine Chough, using measurements taken on 178 males and 144 females. A small amount of size dimorphism appeared in all morphological characters, and weight was the most dimorphic character. To identify if Alpine Choughs mate assortatively, measurements of mates were compared in 76 pairs. A positive assortative mating was found on tarsus length, and a small positive trend is suggested between body condition of partners, but that needs to be confirmed with a larger sample size.
Thirty-Year Bird Population Trends in an Unfragmented Temperate Deciduous Forest: Importance of Habitat Change
Authors: Holmes Richard T. , Sherry Thomas W. 
Published: September 2019

AbstractAbundances of forest birds in an unfragmented, undisturbed, and relatively mature temperate deciduous forest at the Hubbard Brook Experimental Forest, New Hampshire, changed markedly between 1969 and 1998. Total numbers of birds (all species combined) declined from 210–220 individuals/10 ha in the early 1970s to 70–90/10 ha in the 1990s. Of the 24 regularly occurring species, 12 decreased significantly (four to local extinction), three increased significantly, and nine remained relatively constant in abundance. Nine of the 12 declining species were Neotropical migrants. Most species exhibited similar trends on Breeding Bird Survey (BBS) routes in New Hampshire during the same 30 year period and on three replicate study sites in nearby sections of the White Mountains from 1986–1998. Probable causes of trends were diverse and differed among species. Most could be accounted for by individual species' responses to events occurring primarily in the local breeding area. The most important local factor affecting bird abundance was temporal change in forest vegetation structure, resulting from natural forest succession and local disturbances. Four species that declined markedly and in some cases disappeared completely from the study plot (Least Flycatcher, Empidonax minimus; Wood Thrush, Hylocichla mustelina; Philadelphia Vireo, Vireo philadelphicus; and American Redstart, Setophaga ruticilla) appear to attain peak abundance in early or mid successional forests. Species preferring more mature forests, such as Black-throated Green Warbler (Dendroica virens) and Ovenbird (Seiurus aurocapillus), increased significantly in abundance over the 30 year study. Other important factors influencing bird abundances were food availability and events in the migratory and winter periods. Nest-predation rates, although varying among years, showed no long-term pattern that would account for population declines, and brood parasites were absent from this forest. Findings from this study demonstrate that major changes in bird abundances occur over time even in undisturbed and relatively mature forests, and illustrate the need for considering habitat requirements of individual species and how habitat suitability changes over time when trying to assess the causes of their long-term population trends. The results also imply that any conclusions about the effects of other factors affecting forest bird abundances, such as increased nest predation or brood parasitism associated with habitat fragmentation, must also account for successional changes that may be affecting habitat suitability.
Colony and Population Dynamics of Black-Legged Kittiwakes in a Heterogeneous Environment
Authors: Suryan Robert M. , Irons David B. 
Published: September 2019

AbstractBlack-legged Kittiwakes (Rissa tridactyla) nest at 25 distinct colonies located throughout Prince William Sound that range in size from <20 to >7,000 pairs. Dramatic changes have occurred in the distribution of breeding birds among those colonies during the past few decades (1972–1997). Reproductive success data collected since 1985 confirm that individual colonies are habitat patches of varying quality in space and time. Even with such variation, predictability of habitat quality did occur in short- and long-term (≥3 year) intervals as indicated by significant (P < 0.05) relationships between current (t) and previous year's (t−1, t−2, etc.) reproductive success. Those circumstances provided suitable conditions for testing hypotheses concerning dispersal and recruitment strategies of a long-lived species. Breeding birds responded to both short- and long-term cues and, in general, recruited to the most successful colonies. An apparently lower dispersal propensity and the importance of long-term cues was in contrast to a similar study of kittiwake colonies in France (Danchin et al. 1998). Differences between these studies may be attributed to primary factors controlling habitat quality in Prince William Sound operating in the long-term versus the short-term and the magnitude of scale. Colonies in our study covered a much larger geographic area and therefore, factors such as foraging-site faithfulness, mate retention, and natal philopatry may also have influenced dispersal decisions. Nonetheless, recruitment of kittiwakes in Prince William Sound supported the performance-based conspecific attraction hypothesis, which, in turn, led to an ideal free distribution of breeding birds. Those short-term mechanisms for dispersal and recruitment manifested in a long-term redistribution of nesting kittiwakes from poor breeding conditions in southern Prince William Sound to favorable conditions in northern Prince William Sound. Favorable conditions in northern Prince William Sound were apparently supported by stable or increasing populations of juvenile herring. In contrast, reproductive failures and population declines in southern Prince William Sound were concordant with colonies in the Gulf of Alaska where diets were similar, consisting of primarily capelin (Mallotus villosus) and Pacific sand lance (Ammodytes hexapterus). Those trends corresponded with the influence of Gulf of Alaska waters in southern Prince William Sound and may have been associated with a reported decline in the abundance of key forage species related to a late 1970s regime shift in the Gulf of Alaska.
Factors Governing the Distribution of Swainson's Warbler Along a Hydrological Gradient in Great Dismal Swamp
Authors: Graves Gary R. 
Published: September 2019

AbstractDue to extensive clearing of bottomland forest in the southeastern United States, Swainson's Warbler (Limnothlypis swainsonii) is restricted in many drainages to seasonally inundated buffer zones bordering rivers and swamps. This migratory species is especially vulnerable to flooding because of its ground foraging ecology, but little is known about patterns of habitat occupancy at wetland ecotones. I investigated the physiognomic and floristic correlates of habitat use along a subtle hydrological gradient in the Great Dismal Swamp, southeastern Virginia. Hydrology is the driving force influencing vegetation and the distribution of Swainson's Warbler in that habitat. Foraging and singing stations of territorial males were significantly drier and more floristically diverse than unoccupied habitat. There was scant evidence that the distribution and abundance of particular plant species, including giant cane (Arundinaria gigantea), influenced habitat selection. Instead, Swainson's Warbler seems to evaluate potential territories on the basis of multiscale physiognomic, hydrological, and edaphic characteristics. Territories were characterized by extensive understory thickets (median = 36,220 small woody stems and cane culms per hectare; range, 14,000–81,400/ha), frequent greenbriar tangles, deep shade at ground level, and an abundance of leaf litter overlying moist organic soils. Those sites occurred most frequently in relatively well-drained tracts of broad-leaf forest that had suffered extensive canopy damage and windthrow. Data suggest a preference for early successional forest in the current landscape or disturbance gaps in primeval forest. Because territories in otherwise optimal habitat are abandoned when flooding extends into the breeding season, it is recommended that the water table be maintained at subsurface levels from late March through September in natural areas managed primarily for this species. Direct and indirect environmental factors that influence the breeding biology of the warbler are summarized in an envirogram.
Activity Patterns and Effect of Ticks on Growth and Survival of Tropical Roseate Tern Nestlings
Authors: Ramos Jaime A. , Bowler John , Davis Laura , Venis Sarah , Quinn John , Middleton Carole 
Published: September 2019

AbstractPatterns of abundance of the seabird tick Amblyomma loculosum and their effects on Roseate Tern (Sterna dougallii) nestling growth, fledging age, and survival are described on Aride Island, Seychelles, in 1997–1999. Female ticks attached to nestlings from 4 to 14 days (to engorge) whereas male ticks attached for 1–3 days. The linear growth rate of birds carrying female ticks (0.24 g/day) was significantly different from that of nonparasitized nestlings of the same age and similar (or even lower) hatching weight (4.07 g/day). Parasitized nestlings that fledged did so 5.2 days later than nonparasitized nestlings of similar age. Only 37.5% of the nestlings infested with female ticks fledged compared with 83.3% of the noninfested nestlings. During the successful 1998 breeding season, around 100 nestlings died from tick infestation (24.3% of the nestling deaths). Ticks appeared to accelerate nestling mortality during periods of food shortage. Despite an annual difference of two weeks in the timing of breeding of the Roseate Terns between 1997 and 1998, adult ticks parasitized nestlings in July, with an infestation peak occurring between 8–12 July in both years. However, in 1997, nestlings were parasitized at a younger age, suggesting that ticks (nymph stage) must attach to Roseate Tern adults as soon as they make a nest scrape (usually in May). Ironically, the frequent breeding failures of the Roseate Terns will result in lower infestation levels in subsequent years, which will benefit the birds.
Phylogenetic Utility of Avian Ovomucoid Intron G: A Comparison of Nuclear and Mitochondrial Phylogenies in Galliformes
Authors: Armstrong Margaret H. , Braun Edward L. , Kimball Rebecca T. 
Published: September 2019

Abstract
A novel nuclear marker, the avian ovomucoid intron G (OVOG) was sequenced from 19 galliform taxa. Results of the phylogenetic analyses using OVOG were compared to those obtained using the mitochondrial cytochrome b (cytb) gene to determine the phylogenetic utility of OVOG. OVOG appeared to have strong phylogenetic signal for reconstructing relationships among genera and families, and the only difference between OVOG and cytb was in the placement of the New World quail (Odontophoridae). Genetic distances estimated using OVOG are approximately half of those estimated using cytb, although that relationship was not linear. OVOG exhibited patterns of nucleotide substitution very different from cytb, with OVOG having little base compositional bias, a relatively low transition–transversion ratio, and little among-site rate heterogeneity.
Stable-Isotope Analysis of Canvasback Winter Diet in Upper Chesapeake Bay
Authors: Haramis G. Michael , Jorde Dennis G. , Macko Stephen A. , Walker Jane L. , Karasov W. H. 
Published: September 2019

Abstract
A major decline in submerged aquatic vegetation (SAV) in Chesapeake Bay has altered the diet of wintering Canvasbacks (Aythya valisineria) from historically plant to a combination of benthic animal foods, especially the ubiquitous Baltic clam (Macoma balthica), supplemented with anthropogenic corn (Zea mays). Because the isotopic signature of corn is readily discriminated from bay benthos, but not SAV, we used stable-isotope methodology to investigate the corn–SAV component of the winter diet of Canvasbacks. Feeding trials with penned Canvasbacks were conducted to establish turnover rates and fractionation end-point loci of δ13C and δ15N signatures of whole blood for individual ducks fed ad libitum diets of (1) Baltic clams, (2) Baltic clams and corn, and (3) tubers of wild celery (Vallisneria americana). Turnover time constants averaged 4.5 weeks, indicating that signatures of wild ducks would be representative of bay diets by late February. Isotopic signatures of wild Canvasbacks sampled in February fell on a continuum between end-point loci for the Baltic clam and the combination Baltic clam and corn diet. Although that finding verifies a clear dependence on corn–SAV for wintering Canvasbacks, it also reveals that not enough corn–SAV is available to establish ad libitum consumption for the 15,000+ Canvasbacks wintering in the upper bay. On the basis of mean δ13C signature of bay Canvasbacks (n = 59) and ingestion rates from feeding trials, we estimated that 258 kg corn per day would account for the observed δ13C enrichment and supply 18% of daily energetic needs for 15,000 Canvasbacks. That level of corn availability is so realistic that we conclude that SAV is likely of little dietary importance to Canvasbacks in that portion of the bay.
Avian Nesting Success in Forested Landscapes: Influence of Landscape Composition, Stand and Nest-Patch Microhabitat, and Biotic Interactions
Authors: Rodewald Amanda D. , Yahner Richard H. , Brawn J. 
Published: September 2019

AbstractAlthough area and isolation effects on avian communities in highly fragmented landscapes are well known, importance of landscape composition in more forested landscapes remains poorly understood. We determined if the type (agriculture and silviculture) and extent (percentage within 1 km radius) of disturbance within forested landscapes influenced avian nesting success, and then examined if differences in stand-level habitat structure, nest-patch microhabitat, distance of nests to habitat edges, brood parasitism rates, and nest-predator abundance were potential underlying mechanisms of observed associations between landscape composition and nesting success. We monitored active songbird nests (n = 341), surveyed Brown-headed Cowbirds (Molothrus ater) and nest predators, and measured stand-level and nest-patch microhabitat from May–July 1998 and 1999. Each of 10 study sites was located within contiguous mature forest in central Pennsylvania and contained either agricultural or silvicultural disturbances (n = 5 each). Sites of the two landscape types had similar ranges of disturbance within 1 km (21–55% for agriculture, 18–51% for silviculture). Daily nest survival for all species combined (94.0 ± 0.55 in agriculture and 96.9 ± 0.87 in silviculture) and midstory-canopy nesters (93.8 ± 0.97 in agriculture and 97.4 ± 0.75 in silviculture) were greater within forested landscapes disturbed by silviculture than by agriculture, but rates did not significantly differ between landscapes for ground nesters (92.2 ± 1.32 in agriculture and 94.6 ± 1.63 in silviculture) or understory nesters (95.4 ± 1.60 in agriculture and 95.0 ± 1.47 in silviculture). Nest survival was not significantly associated with disturbance extent. Rates of brood parasitism were low, with only 11% of nests containing cowbird eggs or young. Neither nest fate nor differences in daily nest survival between the two landscape types were explained by variation in brood parasitism rates, stand-level or nest-patch habitat characteristics, or distance of nests to edges. Instead, the lower nest success within forested landscapes disturbed by agriculture was best explained by greater abundances of some avian and small mammalian predators (American Crow [Corvus brachyrhynchos] and squirrels) in those landscapes in one or both years. Results suggest that landscape composition within forested landscapes significantly influences avian nesting success by altering interactions between nest predators and nesting birds.
Nest Defense as Parental Care in the Northern Hobby (Falco subbuteo)
Authors: Sergio Fabrizio , Bogliani Giuseppe , Bildstein K. 
Published: September 2019

AbstractIntensity of nest defense against a human intruder was recorded for 42 male and 43 female Northern Hobbies (Falco subbuteo) from 1992 to 1994. Defense did not vary between repeatedly and rarely visited nests. Except during incubation, intensity of nest defense by females was higher than that by males. For both sexes, defense intensity increased from incubation to fledging, within the nestling stage, and from fledging to the first 10 days of the postfledging period. Intensity of nest defense was positively correlated with brood size in females, but not in males. Experiments with dummy nests showed that defense was effective in deterring nest predation, and that its effect was positively related to its intensity. Hobby nest defense was an individually varying “plastic” trait, probably tuned to the reproductive value of the offspring. Parents apparently trade off the costs and risks of the behavior against the increasing likelihood of offspring survival.