bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Sex and Age on Survival of Northern Flickers: a Six-Year Field Study
Authors: Fisher Ryan J. , Wiebe Karen L. 
Published: September 2019

Abstract
Although many forestry management strategies rely on population estimates of indicator species such as woodpeckers (Picidae), empirical estimates of demographic parameters within this taxon are few. We used program MARK to assess influences of age and sex on apparent survival of adult Northern Flickers (Colaptes auratus) from a six-year mark-recapture study. The top model suggested no differences in apparent survival between the sexes with an overall survival estimate of 0.43 (95% CI: 0.38–0.48). Other models suggested that recapture efficiency differed between the sexes (males: 0.87; females: 0.78), perhaps because males were more philopatric to nest sites. We suggest that high parental investment by male flickers relative to other taxa such as passerines may lead to relatively equal mortality rates between the sexes, rather than the common pattern of female-biased mortality. Survival rates relative to age were constant at least up to the age of three years. Overall, flickers appear to have lower survival than some other woodpecker species and may invest relatively heavily in current reproduction.
Sources of Variation in Survival of Breeding Female Wood Ducks
Authors: Hartke Kevin M. , Grand James B. , Hepp Gary R. , Folk Travis H. 
Published: September 2019

AbstractIn waterfowl, reproduction is physiologically demanding and females are exposed to varying risks of mortality at different periods of the breeding cycle. Moreover, differences among females may influence survival within breeding periods. We captured and fitted female Wood Ducks (Aix sponsa) with radio-transmitters before nest initiation during two breeding seasons to estimate survival and investigate sources of variation in survival. We partitioned the breeding season into three periods (preincubation, incubation, postnesting) according to breeding status of individual females, and used information-theoretic methods to compare models in which daily survival varied among periods, between successful and failed nesting females, and with parameters describing individual heterogeneity. Our analysis suggested that daily survival was best modeled as a function of breeding period, differences between successful and failed nesting females during postnesting, and early incubation body condition of successful females during postnesting. Model-averaged daily survival was 0.9988 (95% CL: 0.9963–0.9996) during preincubation and 1.0 during incubation. Postnesting daily survival was 1.0 for failed nesting females and 0.9948 (0.9773–0.9988) for successful females, suggesting a trade-off between current reproduction and survival. Female age, body condition at capture, nest initiation date, and brood size generally were not useful for explaining variation in survival. Only early incubation body condition was important for modeling survival of successful females during postnesting; however, weight of evidence was limited and the effect on survival was weak. Mortality was greatest for females during preincubation and for females that nested successfully. Results support the hypothesis that brood care is costly for females.
Nest Attributes, Aggression, and Breeding Success of Gulls in Single and Mixed Species Subcolonies
Authors: Ellis Julie C. , Good Thomas P. 
Published: September 2019

Abstract
We investigated attributes of nests, aggressive interactions, and reproductive success in mixed and single species subcolonies of Great Black-backed Gulls (Larus marinus) and Herring Gulls (L. argentatus) on Appledore Island, Maine. Distances to the nearest neighboring nest were smaller for L. argentatus than L. marinus, with greatest distances between nests at edges of subcolonies in both species. More L. argentatus nests had natural screens (vegetation or rock >30 cm tall) adjacent to them than did L. marinus nests, but screen presence did not differ among nest positions within the colony. Clutch size did not differ between species; however, hatching success (number of chicks hatched per nest) was higher in L. argentatus than L. marinus. Fledging success (number of chicks fledged per nest) of L. marinus was greater at nests with heterospecific neighbors, whereas the opposite was true for L. argentatus. For both species, the frequency of aggressive interactions was lower at nests with L. argentatus neighbors. Overall, L. marinus nesting near L. argentatus experienced less aggression and greater reproductive success than those nesting among conspecifics, where intraspecific aggression was relatively high. L. argentatus nesting near L. marinus experienced more aggression and lower reproductive success than those nesting among conspecifics, where intraspecific aggression was relatively low. The costs and benefits of nesting in mixed species colonies may depend on the relative size and aggressiveness of the heterospecifics. Interactions with L. marinus in mixed species colonies may be contributing to the current declines of L. argentatus throughout New England.
Postbreeding Movements of Frigatebirds Tracked with Satellite Telemetry
Authors: Weimerskirch Henri , Le Corre Matthieu , Marsac Francis , Barbraud Christophe , Tostain Olivier , Chastel Olivier 
Published: September 2019

AbstractUsing satellite telemetry, we studied the postbreeding movements of Great (Fregata minor) and Magnificent Frigatebirds (F. magnificens) at two breeding colonies in the Indian and Atlantic Oceans. After breeding failure, 67% of the birds with satellite transmitters remained on the breeding colonies and continued to perform foraging trips similar to those undertaken while breeding. Two Magnificent Frigatebirds that bred at a colony off the coast of French Guiana moved west along the coast of South America, and one of the two reached Trinidad 1400 km away. One Great Frigatebird moved 4400 km from Europa Island in the Mozambique Channel to the Maldive Islands. It roosted there for at least four months, making foraging trips of up to 240 km, mainly to an area known for its high concentration of tuna. These results show that frigatebirds are able to make rapid and directed long-distance dispersal movements to other colonies or roosting sites, although the majority of birds remain based on breeding colonies.
Conflicting Temporal Changes in the Frequency and Intensity of Cowbird Parasitism on Four Common Hosts in Ontario over 130 Years
Authors: McLaren Celia M. , Underwood Todd J. , Sealy Spencer G. 
Published: September 2019

AbstractWe tested the hypothesis proposed by Friedmann (1963) that multiple parasitism (nests with more than one parasitic egg) by Brown-headed Cowbirds (Molothrus ater) is a recent phenomenon associated with increased densities of cowbirds. We used Ontario Nest Records Scheme data to quantify frequencies of parasitism and multiple parasitism on four common host species over the last 130 years. Frequency of multiple parasitism significantly increased over all decades only in Chipping Sparrows (Spizella passerina). We also analyzed data separately before and after 1970 because at about this time cowbird abundance began to stabilize and then decline. Pre-1970, multiple parasitism significantly increased on Chipping Sparrows and Song Sparrows (Melospiza melodia), but neither had significant trends post-1970. There were no significant trends in multiple parasitism on Red-eyed Vireos (Vireo olivaceus) or Northern Cardinals (Cardinalis cardinalis). For all time periods analyzed, there were no significant trends in overall frequency of parasitism on any species. Our results provide limited support for the hypothesis that temporal variation in parasitism patterns has followed changes in cowbird density over the past century.
A Variance-decomposition Approach to Investigating Multiscale Habitat Associations
Authors: Lawler Joshua J. , Edwards Thomas C. 
Published: September 2019

Abstract
The recognition of the importance of spatial scale in ecology has led many researchers to take multiscale approaches to studying habitat associations. However, few of the studies that investigate habitat associations at multiple spatial scales have considered the potential effects of cross-scale correlations in measured habitat variables. When cross-scale correlations in such studies are strong, conclusions drawn about the relative strength of habitat associations at different spatial scales may be inaccurate. Here we adapt and demonstrate an analytical technique based on variance decomposition for quantifying the influence of cross-scale correlations on multiscale habitat associations. We used the technique to quantify the variation in nest-site locations of Red-naped Sapsuckers (Sphyrapicus nuchalis) and Northern Flickers (Colaptes auratus) associated with habitat descriptors at three spatial scales. We demonstrate how the method can be used to identify components of variation that are associated only with factors at a single spatial scale as well as shared components of variation that represent cross-scale correlations. Despite the fact that no explanatory variables in our models were highly correlated (r < 0.60), we found that shared components of variation reflecting cross-scale correlations accounted for roughly half of the deviance explained by the models. These results highlight the importance of both conducting habitat analyses at multiple spatial scales and of quantifying the effects of cross-scale correlations in such analyses. Given the limits of conventional analytical techniques, we recommend alternative methods, such as the variance-decomposition technique demonstrated here, for analyzing habitat associations at multiple spatial scales.
Sources and Expectations for Hierarchical Structure in Bird-habitat Associations
Authors: Kristan William B. 
Published: September 2019

Abstract
Hierarchical structure in bird-habitat associations can arise from hierarchical structure in environmental variables and from the scale-dependent responses of birds to habitat. Hierarchical structure in environmental variables is expected to result from interactions between variables that differ in grain size (spatial resolution) and frequency, and should occur commonly. Birds cannot accurately sample habitat characteristics at all spatial scales simultaneously, and the habitat chosen for a given purpose may differ depending on whether a bird samples from high above the ground (which is best for sampling coarse-grained variables) or from ground level (which is best for sampling fine-grained variables). Additionally, birds may exhibit an absolute response to a habitat variable, if it is unsuitable beyond some threshold level, or a relative response, if all available habitat is suitable but some is preferred. Models that can represent hierarchical structure in habitat, as well as hierarchical, scale-dependent responses by birds, should provide researchers the best chance of understanding avian habitat associations.
Effects of Nestling Health on Postfledging Survival of Wood Storks
Authors: Hylton Rebecca A. , Frederick Peter C. , De La Fuente Teresa E. , Spalding Marilyn G. 
Published: September 2019

AbstractLittle is known about the period between fledging and breeding in long-lived birds, including survival rates and factors affecting survival, yet this period may be critical to population regulation. We conducted health exams on 72 nestling Wood Storks (Mycteria americana) aged 4–6 weeks, and monitored survival of these birds via satellite telemetry for up to two years of age. Eighty-two percent of nestlings fitted with transmitters in 2002 (n = 33) survived to fledging. Of these fledglings (n = 27), 44% survived their first year. Second-year survival for the same cohort (n = 12) was 75%. In contrast, 50% of nestlings fitted with transmitters in 2003 (n = 34) survived to fledging, and 6% of fledglings (n = 17) survived the first year. Of the health parameters we measured in large nestlings, white blood cell count was consistently the most closely related to postfledging survival. Significantly elevated heterophil:lymphocyte ratios in 2003 coincided with the observed high colony abandonment that year. After controlling for health parameters, gender also appeared to play a significant role in predicting survival, with males at greater risk of mortality. Hematological factors and gender were both more closely associated with survival in 2003 than in 2002, suggesting these factors may play a greater role in regulating postfledging survival or, in the case of hematology, serve as indicators of poor health in less favorable years when nestling storks are exposed to multiple stressors.
Juvenile Movement and Natal Dispersal of Northern Goshawks in Arizona
Authors: Wiens J. David , Reynolds Richard T. , Noon Barry R. 
Published: September 2019

AbstractWe investigated the departure, transient movement, and local settlement stages of natal dispersal in a population of Northern Goshawks (Accipiter gentilis) on the Kaibab Plateau of northern Arizona. The study included 614 color-banded juveniles produced at 555 nests during 1991–2003, 89 of which were radio-marked during 1998–2001. Radio-marked juveniles initiated dispersal between 71 and 103 days posthatching, and spent between 33 and 66 days in the natal territory after fledging. Our best-fitting proportional hazards models predicted the timing of dispersal as a function of annual differences in the density of primary bird and mammal prey species, weather conditions, and natal brood size. Once dispersal was initiated, most juveniles moved into the more open habitats that surrounded the study area and few eventually returned to breed; first-year fidelity to the local natal population was 28%, and only 69 (11%) color-banded juveniles had entered the territorial population by 2004. Median natal dispersal distance on the Kaibab Plateau was 15.0 km (range  =  0.1–58.1 km), a distance equivalent to about four times the diameter of an average breeding territory (3.8 km). Local settlement behavior of Northern Goshawks appeared to be driven by a combination of intraspecific competition for a limited number of breeding opportunities and inbreeding avoidance. However, much of the natal dispersal process operated at broad spatial scales beyond our study population, indicating a potentially high level of demographic connectivity among naturally fragmented breeding populations in the American Southwest.
Survival and Movements of Juvenile Burrowing Owls During the Postfledging Period
Authors: Morgan Davies J. , Restani Marco 
Published: September 2019

AbstractBurrowing Owl (Athene cunicularia) populations have declined extensively throughout much of North America, and modeling demography may assist conservation. However, few studies have estimated adult survival, and fewer still have determined juvenile survival. In 2003 and 2004 we monitored survival of 40 radio-tagged juveniles during the postfledging period in the Little Missouri National Grassland, North Dakota, where owls nested in black-tailed prairie dog (Cynomys ludovicianus) colonies. Survival averaged 0.57 (95% CI: 0.41–0.73) prior to autumn migration. Mortality was highest during the first two weeks after nest departure when juveniles were flightless, and two to three weeks later when juveniles became independent. Predation or starvation was implicated in most deaths. Distribution and abundance of escape cover (number of prairie dog burrows within 30 m of nests and size of the natal prairie dog colony) did not affect survival. Body condition and brood size at the time of radio-tagging also did not influence survival. Juvenile owls exhibited nest-centered dispersal, and averaged 108 ± 21 (SE) m and 82 ± 17 m from nests at initiation of migration in 2003 and 2004, respectively. Mean dates of departure from the study area were 2 September (± 3 days) 2003 and 24 August (± 2 days) 2004. Mortality during the postfledging period accounted for approximately two-thirds of mortality in the first year of life.
A Productivity Model for Parasitized, Multibrooded Songbirds
Authors: Powell Larkin A. , Knutson Melinda G. 
Published: September 2019

Abstract
We present an enhancement of a simulation model to predict annual productivity for Wood Thrushes (Hylocichla mustelina) and American Redstarts (Setophaga ruticilla); the model includes effects of Brown-headed Cowbird (Molothrus ater) parasitism. We used species-specific data from the Driftless Area Ecoregion of Wisconsin, Minnesota, and Iowa to parameterize the model as a case study. The simulation model predicted annual productivity of 2.03 ± 1.60 SD for Wood Thrushes and 1.56 ± 1.31 SD for American Redstarts. Our sensitivity analysis showed that high parasitism lowered Wood Thrush annual productivity more than American Redstart productivity, even though parasitism affected individual nests of redstarts more severely. Annual productivity predictions are valuable for habitat managers, but productivity is not easily obtained from field studies. Our model provides a useful means of integrating complex life history parameters to predict productivity for songbirds that experience nest parasitism.
Nut Selection by Captive Blue Jays: Importance of Availability and Implications for Seed Dispersal
Authors: Moore Jeffrey E. , Swihart Robert K. 
Published: September 2019

Abstract
We assessed dietary preference of 14 captive Blue Jays (Cyanocitta cristata) for different food types under different conditions of availability. In four separate feeding trials, we provisioned jays with the following: Trial 1, two nuts each of white oak (Quercus alba), pin oak (Q. palustris), black oak (Q. velutina), northern red oak (Q. rubra), and shagbark hickory (Carya ovata); Trial 2, two small and two large red oak acorns; Trial 3, two germinating and two nongerminating white oak acorns; and Trial 4, one large red oak acorn, one large white oak acorn, and one shagbark hickory nut. We used discrete choice models to describe selection under conditions of changing choice sets. Blue Jays displayed a clear preference for pin oak and strong avoidance of red oak acorns when alternative foods were available. White oak and black oak acorns were selected intermediately. Shagbark hickory nuts were never used. Correlation coefficients suggested that preference was inversely related to seed size and the proportion of seed consisting of hard seed coat. In the absence of alternative food items, small red oak acorns were readily taken, whereas large red oak acorns were mostly avoided but still used by some birds. These results highlight the importance of considering food availability when making conclusions about preference, and lend support to the hypothesis that Blue Jays can be important dispersers of even less-preferred oak species. We discuss the potential as well as the limitations for Blue Jays to act as seed dispersers, with respect to postglacial range expansion of fagaceous tree species, and in the context of present-day dispersal in regions where forests are highly fragmented.
Seasonal Differences in Immunological Condition of Three Species of Thrushes
Authors: Owen Jennifer C. , Moore Frank R. 
Published: September 2019

Abstract
Migratory birds are exposed to a diverse pathogen fauna by virtue of their long-distance travels. Although the immune system is an organism's primary defense against pathogenic microorganisms, few studies have investigated avian immune function during migration, much less shown seasonal differences in immune function. We describe the immunological condition of three intercontinental migratory species, Swainson's Thrush (Catharus ustulatus), Veery (C. fuscescens), and Wood Thrush (Hylocichla mustelina) during spring migration. In addition, we compare their immunological condition with conspecifics captured during fall migration and during the breeding season to provide a frame of reference for the spring immunological data. Measures of immunological condition presented include total leukocyte count, heterophil:lymphocyte (H:L) ratio, heterophil and lymphocyte counts, hematocrit, and IgG titers. In addition, we assessed each bird's energetic condition by measuring body mass and calculating a size-corrected condition index. Migrating birds had lower leukocyte and lymphocyte counts, lower hematocrit, reduced fat stores, and higher H:L ratios relative to nonmigrating individuals sampled during the breeding season. We also found that birds sampled during spring migration had lower lymphocyte counts and reduced fat stores, and higher heterophil counts and H:L ratios than fall migrants. Our results suggest that migrating birds are immunocompromised compared with conspecifics during the breeding season. Furthermore, compared with conspecifics sampled after a shorter overland flight, migrants sampled after crossing the Gulf of Mexico exhibited higher H:L ratios, which is indicative of heightened energetic stress.
Coevolutionary Interactions Between Common Cuckoos and Corn Buntings
Authors: Antonov Anton , Stokke Bård G. , Moksnes Arne , RØskaft Eivin 
Published: September 2019

AbstractAlthough Old World buntings (Emberizinae) may be considered suitable Common Cuckoo (Cuculus canorus) hosts, there is at present no evidence that any of the European species are regularly parasitized. Most historical parasitism records refer to the Yellowhammer (Emberiza citrinella) and Reed Bunting (E. schoeniclus). Both of these species reject almost 100% of experimentally added nonmimetic eggs, and also a considerable proportion of experimentally added conspecific eggs, showing exquisite egg discrimination abilities. In this paper, we report Common Cuckoo parasitism and egg rejection behavior in a Bulgarian population of another Old World Emberizinae, the Corn Bunting (Miliaria calandra). We found this species was regularly parasitized (9%, 8 of 90 nests) and that the parasitism rate was consistent among the three years of our study. Naturally laid Common Cuckoo eggs were fairly good mimics of host eggs and most were accepted (5 of 7). The Corn Bunting proved to be a suitable Common Cuckoo host as we recorded a successfully fledged cuckoo chick. Unlike Yellowhammers and Reed Buntings, Corn Buntings rejected only 42% (16 of 38) of experimentally introduced nonmimetic model Common Cuckoo eggs and none of the experimentally introduced conspecific eggs (n  =  13). Parasitized nests had more and higher trees in the vicinity than unparasitized nests and breeding habitat characteristics may explain the difference in egg discrimination abilities between Corn Buntings and other Old World Emberizinae.
Do Nearctic Northern Wheatears (Oenanthe Oenanthe Leucorhoa) Migrate Nonstop to Africa?
Authors: Thorup Kasper , Thorup Kasper , Ortvad Troels Eske , RabØl JØrgen 
Published: September 2019

AbstractWe present data suggesting that Northern Wheatears (Oenanthe oenanthe leucorhoa) breeding in West Greenland and Canada may be able to accomplish migration to their wintering grounds in West Africa in one direct, transatlantic crossing of more than 4000 km (great circle distance). This conclusion is based on analyses of wing lengths, body weights, and timing of departure from West Greenland and arrival on an island 350 km off the coast of Morocco. Previously, it has been suggested that Nearctic wheatears migrate to Africa by a two-step journey, the first leg comprising a shorter transatlantic crossing to western Europe. A long, direct flight has previously been considered unfeasible as the predicted flight costs were considered to be too high. However, recent insights in aerodynamic theory make these long ocean crossings appear more feasible, especially when taking the use of tailwinds into account.