bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal Fruit Preferences for Lipids and Sugars by American Robins
Authors: Lepczyk Christopher A. , Murray K. Greg , Winnett-Murray Kathy , Bartell Paul , Geyer Eric , Work Timothy 
Published: September 2019

AbstractFruit preference by birds is a complex process based upon the morphology and spatial arrangement of fruits and on the physiological needs and capabilities of birds. In North America, most fruits can be divided into two groups based on nutritional content: those rich in sugars relative to lipids, and those rich in lipids relative to sugars. To investigate how fruit preference may change seasonally and to determine if it is correlated with physiological state, we designed a simple laboratory experiment using American Robins (Turdus migratorius) and artificial fruits. During summer and autumn, we offered eight robins a choice between synthetic sugar-rich and lipid-rich fruits of equal caloric value and then measured food intake and assimilation efficiency for each fruit type. Overall, robins preferred sugar-rich to lipid-rich fruits during both seasons. Robins had a higher assimilation efficiency for sugars than for lipids during both seasons, although assimilation efficiency of lipids increased significantly from summer to autumn. During experiments, robins consumed significantly more sugar-rich than lipid-rich fruits in summer but not in autumn. Coupling fruit intake with assimilation efficiency indicates that in summer, robins had a higher rate of energy gain from sugars than from lipids, but by autumn the rate of energy gain from lipids increased to nearly the same level as that from sugars. Our results suggest that robins prefer sugar-rich fruits because of their simple and fast rate of digestion, enabling higher rates of energy gain, but that lipid-rich fruits become important with the onset of autumn.
Effects of Malaria on Activity Budgets of Experimentally Infected Juvenile Apapane (Himatione Sanguinea)
Authors: Yorinks Nancy , Atkinson Carter T. 
Published: September 2019

AbstractWe used behavioral, physiological, and parasitological measures to document effects of acute malarial infections on activity budgets of experimentally infected juvenile Apapane (Himatione sanguinea). Five of eight birds died within 20 to 32 days after exposure to a single infective mosquito bite. Infected Apapane devoted less time to locomotory activities involving flight, walking or hopping, and stationary activities such as singing, preening, feeding, and probing. The amount of time spent sitting was positively correlated with parasitemia and increased dramatically after infection and between treatment and control groups. Birds that succumbed to infection experienced a significant loss of body mass and subcutaneous fat, whereas surviving Apapane were better able to maintain body condition and fat levels. When rechallenged with the parasite five months after initial infection, surviving birds experienced no increase in parasitemia, indicating that they had become immune to reinfection. Regardless of the outcome, infected birds experienced acute illness that would have left them unable to forage or to escape from predators in the wild.
Predation of Natural and Artificial Nests in a Southern Pine Forest
Authors: Buler Jeffrey J. , Hamilton Robert B. 
Published: September 2019

Abstract
We compared predation of artificial open-cup nests baited with Japanese Quail (Coturnix coturnix) eggs with predation of natural open-cup nests during 1997 and 1998 in a Louisiana pine forest to assess the assumption that predation of artificial nests is an index to that of natural nests. Cameras were placed at randomly selected natural and artificial nests in shrubs to document predators. Predation at artificial-nest plots was positively correlated with predation at adjacent natural-nest plots overall, although inconsistently by year. Artificial nests were almost exclusively depredated by corvids, but quail eggs were too large to be broken by small-mouthed mammalian predators. American Crows (Corvus brachyrhynchos) appeared to be important predators of natural nests. Predation of natural nests was independent of predation at other nests, but predation of artificial nests by crows was spatially and temporally clumped. Crows may have learned the location of artificial-nest plots, and predation of artificial nests increased significantly between years, contrary to predation of natural nests. Predation of artificial nests did not exhibit seasonal variation like that of natural nests. Overall, predation of artificial shrub nests did not accurately mimic that of natural shrub nests. Changes in procedures for artificial-nest studies that reduce spatially and temporally clumped predation and prevent the exclusion of small-mouthed predators could increase the suitability of such studies as a model for predation at natural nests. However, the difference in labor effort between studies of natural nests versus artificial nests that incorporate the changes we recommend likely would disappear, which would reduce the attractiveness of artificial-nest studies as an experimental model.
Movement Patterns of Wintering Grassland Sparrows in Arizona
Authors: Gordon Caleb E. 
Published: September 2019

AbstractI used mark-recapture analysis and radio telemetry to characterize winter movement patterns of six grassland sparrows in southeastern Arizona. Mark-recapture data were generated by banding birds captured during repeated flush-netting sessions conducted on a series of 7-ha plots over three consecutive winters. This resulted in 2,641 captures of 2,006 individual sparrows of the six species. Radio telemetry was conducted concurrently on 20 individuals of four of these species. Recapture data and radio telemetry indicated that Cassin's Sparrow (Aimophila cassinii) and Grasshopper Sparrow (Ammodramus savannarum) were the most sedentary, followed by Baird's Sparrow (Ammodramus bairdii), Vesper Sparrow (Pooecetes gramineus), Savannah Sparrow (Passerculus sandwichensis), and Brewer's Sparrow (Spizella breweri). Grasshopper, Baird's, Savannah, and Vesper sparrows tended to remain within fixed home ranges during winter. With the exception of Savannah Sparrows, whose movement behavior varied among study sites, movement patterns remained constant within species across years and study sites despite radical fluctuations in the absolute and relative abundances of all species. Interspecific differences in movement pattern suggest that species in this system partition niche space according to the regional-coexistence mechanism. Abundances of the most sedentary species, Cassin's, Grasshopper, and Baird's sparrows, were poorly or negatively correlated with summer rainfall at the between-year landscape scale, whereas abundances of the more mobile Savannah, Vesper, and Brewer's sparrows were strongly positively correlated. This is consistent with the theoretical prediction that movement constrains large-scale habitat selection, favoring mobile species in fragmented environments.
Tracing Nutrient Allocation to Reproduction With Stable Isotopes: A Preliminary Investigation Using Colonial Waterbirds of Great Slave Lake
Authors: Hobson Keith A. , Sirois Jacques , Gloutney Mark L. 
Published: September 2019

AbstractWe investigated the use of stable-isotope analysis as a direct means of tracing allocation of endogenous protein and lipid reserves to reproduction in five gulls (Larus canus, L. delawarensis, L. californicus, L. argentatus, L. philadelphia), four terns (Sterna caspia, S. hirundo, S. paradisaea, Chlidonias niger), and one jaeger (Stercorarius parasiticus) breeding on Great Slave Lake (GSL) in the Northwest Territories. Our approach was based on assumptions that (1) body tissues of birds just arriving at GSL from their assumed marine-associated wintering habitats would have stable-isotope ratios more enriched than those of birds in equilibrium with the local GSL foodweb, and (2) mobilization of these reserves to reproduction could be traced by the isotopic measurement of egg macronutrients. As predicted, the pectoral muscle of six species of arriving birds was more enriched in 13C (x̄ = −21.5‰) and 15N (x̄ = 12.7‰) than was that of postbreeding birds (13C, x̄ = −23.5‰; 15N, x̄ = 9.9‰) or hatching-year birds raised at GSL (13C, x̄ = −24.3‰; 15N, x̄ = 9.0‰). Abdominal fat of arriving Herring Gulls and Mew Gulls was more enriched in 13C (x̄ = −19.7‰) than the fat of other species (x̄ = −23.4‰), indicating lipids of marine origin. We compared isotope values of the local GSL foodweb with dietary values predicted from isotope measurements of egg macronutrients if diets were entirely derived at GSL. Isotopic analysis of lipid-free egg yolk, yolk lipid, and shell carbonate suggested that for most species, little if any endogenous protein reserves were used for reproduction, with the possible exception of Caspian Terns, whose egg protein and egg lipid values, and Common Terns, whose egg protein values, were more enriched in 13C than those of the other species. Although endogenous nutrient reserves likely were important to birds during migration and the initial settling period at GSL, local food supplies were adequate to provide nutrients for reproduction.
Systematic Revision and Biogeography of the Herpsilochmus Pileatus Complex, With Description of a New Species From Northeastern Brazil
Authors: Whitney Bret M. , Pachecom José Fernando , Buzzetti Dante R. C. , Parrini Ricardo 
Published: September 2019

AbstractStudy of vocalizations of Herpsilochmus antwrens in northeastern Brazil revealed that the traditional H. pileatus complex is comprised of not two but three species-level taxa. We show that the systematics and biogeography of the group have been based on an unnamed species that has been called H. pileatus for most of this century. Here, we name this “new” species and conclude that its several morphological and vocal distinctions clearly set it apart from other members of the complex. True H. pileatus, as determined through comparison of the lectotype with recently collected specimens and from the distribution of recordings, is confined to southern coastal Bahia. Morphological and vocal analyses suggest that H. pileatus and H. atricapillus are each other's closest relatives. We provide a simple key to diagnostic plumage and mensural characters to permit identification of museum specimens. An extensive series of specimens demonstrated that H. atricapillus includes two male morphs. Geographic overlap of pure morphs in southern Goiás, and the existence of some apparent intermediates in this general area, suggest secondary contact of two weakly differentiated populations, perhaps along complex habitat gradients. Analysis of recordings of H. atricapillus disaggregated geographically and by male morph revealed no diagnostic (by criteria of Isler et al. [1998]) variation within that species, although average measures of overall pace and pace of three sections of loudsongs differed between the morphs by approximately 20%, which we interpret as another indication of incipient differentiation. Revision of the Herpsilochmus pileatus complex provides a case in point for the fundamental role in conservation of both field and taxonomic research and demonstrates the importance of examination of type specimens and inclusion of topotypical samples (whether anatomical, biochemical, or tape recordings) in studies of taxonomy and systematics.
Egg Rejection by Cowbird Hosts in Grasslands
Authors: Peer Brian D. , Robinson Scott K. , Herkert James R. 
Published: September 2019

AbstractWe tested Field Sparrows (Spizella pusilla), Vesper Sparrows (Pooecetes gramineus), Lark Sparrows (Chondestes grammacus), Grasshopper Sparrows (Ammodramus savannarum), Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Western Meadowlarks (S. neglecta) to determine whether the low level (<10%) of observed parasitism by Brown-headed Cowbirds (Molothrus ater) on these grassland hosts is a result of egg rejection. Western Meadowlarks rejected 78% of artificial and real cowbird eggs, Eastern Meadowlarks rejected 36% of artificial cowbird eggs, and Dickcissels rejected 11% of artificial cowbird eggs. None of the other hosts regularly rejected cowbird eggs. Thus, egg rejection may account for some, but not all, of the low level of observed parasitism on grassland hosts in the Midwest. Meadowlarks were also tested with nonmimetic eggs, and the remaining hosts were tested with undersized mimetic and nonmimetic eggs when possible. All hosts, with the exception of the Field Sparrow, demonstrated some level of rejection of the nonmimetic eggs. These results suggest that some grassland hosts, which apparently have been in contact with cowbirds the longest, have evolved some form of rejection behavior that might have selected for mimetic eggs in cowbirds. The intermediate levels of rejection by both species of meadowlarks also may indicate that rejection is increasing in these populations.
Is Reproduction by Tree Swallows Cost Free?
Authors: Murphy Michael T. , Armbrecth Brian , Vlamis Ekaterini , Pierce Aaron 
Published: September 2019

Abstract
We manipulated brood sizes of Tree Swallows (Tachycineta bicolor) in 1996 and 1997 to test for the existence of intra- and intergenerational costs of reproduction. Modal clutch size was six eggs, but experimental brood sizes ranged from two to nine young. Nestling starvation was higher in 1996 (and dependent on brood size) than in 1997, but in both years enlargement of brood size resulted in increased productivity. Nestling mass near fledging was negatively correlated with brood size, but tarsus length and wing chord were not. Food deliveries by parents increased steadily between broods of two to six young but then remained constant between broods of six to nine young. The loss of female mass between incubation and the end of the nestling period was positively related to the pair's total feeding effort, and female mass near fledging declined with increasing brood size. The latter decline disappeared, however, when broods of nine were omitted. Adult return rate (1996 to 1997) was highest among birds that raised enlarged broods. Our results, and a review of other studies of Tree Swallows, suggest that broods of seven or eight young can be raised without costs to the parents or young, and it appears that costs associated with feeding young have not influenced annual fecundity of Tree Swallows. Rather, egg production is most likely limited by energy availability to laying females. A major cost of reproduction for Tree Swallows probably arises from nest-site competition in that early arrival in spring to obtain nest sites exposes adults to high risks of death from starvation.
Clearcut Stand Size and Scrub-Successional Bird Assemblages
Authors: Krementz David G. , Christie Jeffrey S. 
Published: September 2019

Abstract
We investigated the effects of clearcut stand size on species richness, reproductive effort, and relative abundance of scrub-successional birds and the entire bird assemblage at the Savannah River Site in South Carolina. We used standardized mist-net grids to mark and recapture birds in clearcuts replanted with longleaf pine (Pinus palustris) in stands of 2 to 57 ha that were two to six years old. Species richness for the entire bird assemblage was not explained by stand size (P = 0.67), stand age (P = 0.95), or the interaction of these two variables (P = 0.90). Similarly, species richness of scrub-successional birds was not explained by stand size (P = 0.63), stand age (P = 0.55), or the interaction of stand size and stand age (P = 0.35). Regressing species richness on clearcut stand size, we found a significant negative relationship between these variables for the entire bird assemblage (P = 0.01) and for scrub-successional birds (P = 0.02). The ratio of juveniles to adults in mist-net samples varied by year (P = 0.04), but neither clearcut size (P = 0.23) nor the interaction of clearcut size and year (P = 0.25) was related to the ratio of juveniles to adults in the sample. We found no relationship between the frequency of capture of any category of birds and stand size (scrub-successional, P = 0.52; woodland, P = 0.77; combined sample, P = 0.55). Neither bird-species richness, reproductive effort, nor relative abundance differed across clearcut stand sizes. Clearcut stand size does not appear to be an important management variable if variation in species richness, reproductive effort, or relative abundance are objectives. We suggest that even-aged forestry is a useful tool for managing birds in the southeastern United States.
Geographic Variation in the Organization of Song Sparrow Repertoires
Authors: Peters Susan , Searcy William A. , Beecher Michael D. , Nowicki Stephen 
Published: September 2019

Abstract
We asked whether geographic variation exists in the complexity of song repertoires in Song Sparrows (Melospiza melodia) by quantitatively comparing four measures of repertoire organization across four geographically distant populations: (1) repertoire size (the number of distinct song types), (2) the number of “minimal units of production” per repertoire, (3) mean similarity among variants of the same song type (“within-type” similarity), and (4) mean similarity among song types in a repertoire (“between-type” similarity). We found significant geographic differences among populations in three of these four measures, with mean similarity among song types being the exception. In general, relatively sedentary populations in North Carolina and Washington were more similar to each other than to migratory populations in Pennsylvania and Maine. Contrary to our expectation based on prior interspecific analyses of variation in repertoire complexity, the relatively sedentary populations in our sample had more complex repertoires than did the more migratory populations. The origin and functional significance of population differences in repertoire complexity in this species remain uncertain.
Use of Lice to Identify Cowbird Hosts
Authors: Hahn D. Caldwell , Price Roger D. , Osenton Peter C. 
Published: September 2019

AbstractBrood-parasitic nestlings have a unique opportunity to encounter host-specific lice (Phthiraptera). Lice are permanent ectoparasites found strictly on the body of the host, and they are transferred almost exclusively by bodily contact during copulation and care of young. We investigated whether Brown-headed Cowbird (Molothrus ater) nestlings become infested with lice from their host parents and carry these after fledging, in effect bearing ectoparasite indicators of the species that raised them. Examining lice on cowbirds to identify foster parents would be less costly than determining parasitism patterns in the conventional way by finding many host nests. The 244 cowbird fledglings that we examined carried 11 species and 6 genera of lice, almost the entire spectrum of louse genera known from passerines. We also examined 320 songbirds from 30 species of hosts. As a group, the diversity of louse species on hosts was comparable to that on fledgling cowbirds: 13 species and 7 genera. In contrast, most individual host species yielded only one or two louse species, significantly fewer than on cowbird fledglings. Of 44 fledgling cowbirds with lice, 11 were linked with probable avian foster parents, and 18 other fledglings were linked with one of two possible foster parents. We conclude that cowbird fledglings carry away host lice and that our technique provides a partial assessment of parasitism patterns. The incomplete state of louse taxonomy requires that users of the technique obtain a reference collection of lice from host species in addition to the sample collection from cowbird fledglings. Lice from cowbird fledglings can be identified by a taxonomist and linked to particular host species, and the principal difficulty is the scarcity of skilled louse taxonomists. We also found an unusually rich louse fauna on 219 adult cowbirds, which supports the interpretation that lack of opportunity due to physical isolation has been the fundamental factor in the host specificity of lice in certain avian orders.
Parental Correlates of Offspring Sex Ratio in Eurasian Oystercatchers
Authors: Heg D. , Dingemanse N. J. , Lessells C. M. , Mateman A. C. 
Published: September 2019

AbstractWe investigated hatchling and fledgling sex ratios in Eurasian Oystercatchers (Haematopus ostralegus) using random amplified polymorphic DNA markers. The overall hatchling (53% males, n = 374 hatchlings from 177 broods) and fledgling (49% males, n = 51) sex ratio did not differ significantly from unity. Hatchling and fledgling sex ratios were not correlated with laying date, clutch size, brood size, egg-laying sequence, territory quality, male age, or male breeding experience, but hatchling sex ratio was positively correlated with age and breeding experience of females (0.05 < P < 0.075, n = 71). Older females produced more sons irrespective of the position of the offspring in the egg-laying sequence. Fledging mass was not correlated with female age, so the Trivers and Willard (1973) hypothesis is unlikely to explain our results. Sons dispersed less than daughters, so the local resource competition hypothesis of Clark (1978) might apply. The adaptive significance of a male-biased sex ratio in clutches produced by older females is speculative because the costs and benefits of dispersing versus philopatric offspring to parents and offspring are largely unknown.
Predator Responses to Similarity and Dispersion of Artificial Nest Sites: Implications for the Structure of Boreal Forest Songbird Communities
Authors: Rangen Sheila A. , G. Clark Robert , Hobson Keith A. 
Published: September 2019

AbstractRelatively little is known about the role of predation in shaping patterns of coexistence and nest dispersion of songbird species. It has been hypothesized that predators diversify songbird communities by preying more heavily on individuals and species with greatest similarity in nest-site use. To investigate the importance of predation, we tested how predators responded to assemblages of artificial songbird nests that varied in nest-site placement, vegetation features, and nest dispersion patterns in boreal forest of west-central Alberta, Canada. Variability among nest sites was achieved by deploying wicker nests throughout a gradient of vegetation cover and by deploying nests to simulate two- and three-species assemblages. Two-species assemblages, comprising 20 simulated White-throated Sparrow (Zonotrichia leucophrys) and 3 simulated Hermit Thrush (Catharus guttatus) nests, and three-species assemblages, comprising 10 simulated White-throated Sparrow, 9 simulated Hermit Thrush, and 4 simulated Chipping Sparrow (Spizella passerina) nests, were deployed in eight replicate plots. We hypothesized that predators would be more adept at locating and depredating (1) nests characterized by similar vegetation features in nest patches; (2) nests of similar appearance or nest guild; and (3) clumped versus randomly distributed nests. Contrary to predictions, predation did not increase as variance in vegetation of nest sites decreased across 16 nest-predation plots, nor did variance in vegetation of successful nests increase as predation level increased across 15 nest-predation plots. The addition of one species' nest type to assemblages did not result in lower predation rates. Predators also did not depredate more clumped nests than randomly distributed nests. Overall, predation did not appear to influence patterns of songbird species coexistence or nest dispersion. Abilities of predators to discriminate among less-similar versus more-similar nest sites and nest-dispersion patterns are probably species-specific; that is probably related to the hunting behavior of predators (i.e. use of olfactory and visual cues) and territory size.