bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Relationship Between Habitat Characteristics and Demographic Performance of Northern Spotted Owls in Southern Oregon
Authors: Dugger Katie M. , Wagner Frank , Anthony Robert G. , Olson Gail S. 
Published: September 2019

AbstractWe used data from Northern Spotted Owl (Strix occidentalis caurina) territories to model the effects of habitat (particularly intermediate-aged forest stand types), climate, and nonhabitat covariates (i.e., age, sex) on owl reproductive rate and apparent survival in southwestern Oregon. Our best model for reproductive rate included an interaction between a cyclic, annual time trend and male breeding experience, with higher reproductive rates in even years compared to odd, particularly for males with previous breeding experience. Reproductive rate was also negatively related to the amount of winter precipitation and positively related to the proportion of old-growth forest near the owl territory center. Apparent survival was not associated with age, sex, climate or any of the intermediate-aged forest types, but was positively associated with the proportion of older forest near the territory center in a pseudothreshold pattern. The quadratic structure of the proportion of nonhabitat farther from the nest or primary roost site was also part of our best survival model. Survival decreased dramatically when the amount of nonhabitat exceeded ∼50%. Habitat fitness potential estimates (λ̂h) for 97 owl territories ranged from 0.29–1.09, with a mean of 0.86 ± 0.02. Owl territories with habitat fitness potentials <1.0 were generally characterized by <40%–50% old forest habitat near the territory center. Our results indicate that both apparent survival and reproductive rate are positively associated with older forest types close to the nest or primary roost site. We found no support for either a positive or negative direct effect of intermediate-aged forests on either survival or reproductive rate.
Effects of Savanna Restoration on the Foraging Ecology of Insectivorous Songbirds
Authors: Hartung Sarah C. , Brawn Jeffrey D. 
Published: September 2019

Abstract
We studied the foraging behavior of insectivorous songbirds during the breeding season at four sites in Illinois, each with restored open-canopy savanna habitat (65% mean canopy closure) and closed-canopy forests (89% mean canopy closure). We sampled and compared apparent tree species preference, foliage layer preference, and proportional use of different prey-attack maneuvers in the two habitats. In closed-canopy forests, three of nine songbird species foraged in black oak (Quercus velutina) and white oak (Q. alba) more than expected based on availability, and foraged less than expected in shade-tolerant trees such as sugar maple (Acer saccharum) and red elm (Ulmus rubra). Four species also displayed apparent preferences for black locust (Robinia pseudoacacia) and hackberry (Celtis occidentalis). In contrast, songbirds used tree species according to availability in open-canopy habitat. We observed apparent preferences for the shrub and subcanopy vegetation layers (0–5 m and 6–10 m) in open-canopy habitat and apparent preferences for the subcanopy and lower canopy vegetation layers (6–10 m and 11–15 m) in closed-canopy forests. Relative use of prey-attack maneuvers in open versus closed-canopy habitat was significantly different for the Eastern Wood-Pewee (Contopus virens) and the Great Crested Flycatcher (Myiarchus crinitus), but not for foliage-gleaning species. These results suggest that restoration of oak savannas has important effects on the habitat use and foraging ecology of selected insectivorous birds.
Mallard Duckling Survival in the Great Lakes Region
Authors: Simpson John W. , Yerkes Tina J. , Smith Barry D. , Nudds Thomas D. 
Published: September 2019

AbstractSurvival of young in waterfowl is poorly understood, particularly in regions outside of the traditional prairie breeding areas. Further, traditional methods of survival estimation lack the ability to statistically characterize between the extremes of random and catastrophic mortality events. We estimated Mallard (Anas platyrhynchos) duckling survival rates for 121 broods at nine study sites across the Great Lakes region from 2001–2003, using a novel statistical method that allows for the partitioning of random and correlated mortality processes. Results indicated that survival increased rapidly with age, did not change with hatching dates, did not differ among years, but varied across site-by-year replicates. Rates of random mortality were found to vary among site-years, while rates of correlated mortality varied little across site-years. In contrast to most studies of Mallard duckling survival, seasonal increases in duckling survival were not detected. We speculate that the observed patterns in survival rates with hatching date are related to productivity in Great Lakes brood-rearing wetlands and temperate regional climate.
Further Evidence for Paraphyly of the Formicariidae (Passeriformes)
Authors: Rice Nathan H. 
Published: September 2019

Abstract
The historical relationships of ground antbirds and their relatives have long been unresolved. Here, I present a phylogenetic analysis of ground antbird (Formicariidae) relationships based on DNA sequence data from the cytochrome-b and ND2 genes. Results support novel hypotheses of historical relationships, including two revisions of suboscine taxonomy: (1) paraphyly of the Formicariidae with the tentative inclusion of at least some rhinocryptids (Liosceles, Rhinocrypta, and Scytalopus) in the ground antbird lineage, and (2) placement of Pittasoma with Conopophaga in the Conopophagidae.
Age-Based Plumage Changes in the Lance-Tailed Manakin: A Two-Year Delay in Plumage Maturation
Authors: DuVal Emily H. 
Published: September 2019

Abstract
I investigated the relationship of plumage to age and sex in the Lance-tailed Manakin (Pipridae, Chiroxiphia lanceolata) in the lowlands of western Panama from 1999–2004. I captured birds in mist nets, categorized their plumages, examined them for molt, and followed them for several years to document plumage changes. Male Lance-tailed Manakins exhibited three distinct postjuvenal plumages. Males achieved definitive adult plumage through sequential changes that occurred in the same order as in other Chiroxiphia manakins. Definitive male plumage developed over the same time span as reported for C. caudata but one year faster than C. linearis. Juvenal male plumage was similar to that of females, and 5% of 226 females had plumage similar to formative male plumage. Genetic sexing verified that changes observed late in the formative male plumage unambiguously identified sex and age of individual birds. This information can be used in behavioral studies to identify the age of male Lance-tailed Manakins captured in any of the predefinitive plumage stages.
Intraclutch Egg-Size Variation in Magellanic Penguins
Authors: Rafferty Nicole E. , Boersma P. Dee , Rebstock Ginger A. 
Published: September 2019

Abstract
We investigated patterns and consequences of intraclutch egg-size variation in Magellanic Penguins (Spheniscus magellanicus). First-laid eggs were significantly larger than second-laid eggs, although the mean difference represented only 2% of an average egg's volume. The degree of intraclutch egg-size variation was similar among years and females of different ages. Intraclutch egg-size variation did not affect intraclutch differences in chick hatching weights or fledging success. We found no selective advantage for laying eggs of different sizes. Because both eggs have an equal probability of being lost, chance favors equal provisioning of eggs. Egg volume explained 35% of the variation in hatching weight but did not determine fledging success. Laying order, year, and female age were better predictors of fledging success than egg size. Factors such as laying and hatching order, parental quality, oceanographic conditions, fights, and predation are more important in determining chick survival than are differences in egg size.
Group Living in the Black-Breasted Wood-Quail and the Use of Playbacks as a Survey Technique
Authors: Hale Amanda M. 
Published: September 2019

AbstractI used playbacks of recorded group song to survey and capture Black-breasted Wood-Quail (Odontophorus leucolaemus), a cloud forest endemic, in Monteverde, Costa Rica. This species is abundant in the dense understory of large windbreaks, forest fragments, and continuous forest of the Monteverde Reserve Complex. Mean covey size was four adults (range = 2–9 adults) and mean density, which did not differ between fragmented and continuous forest, was one covey per 3.3 ha. Wood-Quail defended all-purpose group territories and coveys persisted from one year to the next, indicating a group structure that is very different from what is found in most New World quail. A peak in breeding activity occurred at the transition from the wet to the dry season and larger groups produced significantly more juveniles than smaller groups in this population. Playbacks were a useful technique for detecting Black-breasted Wood-Quail; coveys responded to 65% of survey attempts by chorus and approach. By repeating the survey just three times, I was able to detect 91% ± 5% of all coveys that were known from extensive searches to occur in the remnant forest patches of the Monteverde community. The year-round sociality that is seen in this species is due in part to the retention of young on the natal territory beyond the age of sexual maturity. The intriguing relationship between group size and reproductive success in this population suggests the wood-quail may provide the first demonstration of a cooperative breeding system in the Galliformes.
A Hierarchical Model for Regional Analysis of Population Change Using Christmas Bird Count Data, with Application to the American Black Duck
Authors: Link William A. , Sauer John R. , Niven Daniel K. 
Published: September 2019

Abstract
Analysis of Christmas Bird Count (CBC) data is complicated by the need to account for variation in effort on counts and to provide summaries over large geographic regions. We describe a hierarchical model for analysis of population change using CBC data that addresses these needs. The effect of effort is modeled parametrically, with parameter values varying among strata as identically distributed random effects. Year and site effects are modeled hierarchically, accommodating large regional variation in number of samples and precision of estimates. The resulting model is complex, but a Bayesian analysis can be conducted using Markov chain Monte Carlo techniques. We analyze CBC data for American Black Ducks (Anas rubripes), a species of considerable management interest that has historically been monitored using winter surveys. Over the interval 1966–2003, Black Duck populations showed distinct regional patterns of population change. The patterns shown by CBC data are similar to those shown by the Midwinter Waterfowl Inventory for the United States.
A Possible Role for Red Squirrels in Structuring Breeding Bird Communities in Lodgepole Pine Forests
Authors: Siepielski Adam M. 
Published: September 2019

AbstractNest predation is thought to play an important role in structuring certain breeding bird communities. One potential consequence of nest predation is lower recruitment in breeding birds, which may be manifested as lower breeding bird abundance. Lodgepole pine (Pinus contorta ssp. latifolia) forests east and west of the Rocky Mountains became isolated following glacial retreat 12 000 years ago and differ in whether or not red squirrels (Tamiasciurus hudsonicus), which are a key nest predator, are present. Breeding bird abundance in lodgepole pine forests was compared between four ranges with red squirrels and four ranges without red squirrels. Species grouped into canopy and understory nesting guilds were, on average, two and three times more abundant, respectively, in forest ranges without red squirrels than in ranges with red squirrels; no statistically significant differences were found for midstory, ground, or cavity nesters. These results suggest that geographic variation in the presence or absence of red squirrels is likely important in structuring breeding bird communities in lodgepole pine forests across the landscape.
Predicting Regional Abundance of Rare Grassland Birds with a Hierarchical Spatial Count Model
Authors: Thogmartin Wayne E. , Knutson Melinda G. , Sauer John R. 
Published: September 2019

AbstractGrassland birds are among the most imperiled groups of birds in North America. Unfortunately, little is known about the location of regional concentrations of these birds, thus regional or statewide conservation efforts may be inappropriately applied, reducing their effectiveness. We identified environmental covariates associated with the abundance of five grassland birds in the upper midwestern United States (Bobolink [Dolichonyx oryzivorus], Grasshopper Sparrow [Ammodramus savannarum], Henslow's Sparrow [A. henslowii], Sedge Wren [Cistothorus platensis], and Upland Sandpiper [Bartramia longicauda]) with a hierarchical spatial count model fitted with Markov chain Monte Carlo methods. Markov chain Monte Carlo methods are well suited to this task because they are able to incorporate effects associated with autocorrelated counts and nuisance effects associated with years and observers, and the resulting models can be used to map predicted abundance at a landscape scale. Environmental covariates were derived from five suites of variables: landscape composition, landscape configuration, terrain heterogeneity and physiognomy, climate, and human influence. The final models largely conformed to our a priori expectations. Bobolinks and Henslow's Sparrows were strongly sensitive to grassland patch area. All of the species except Henslow's Sparrows exhibited substantial negative relations with forest composition, often at multiple spatial scales. Climate was found to be important for all species, and was the most important factor influencing abundance of Grasshopper Sparrows. After mapping predicted abundance, we found no obvious correspondence in the regional patterns of the five species. Thus, no clearly defined areas exist within the upper midwestern United States where management plans can be developed for a whole suite of grassland birds. Instead, a larger, region-wide initiative setting different goals for different species is recommended.
Cross-scale Correlations and the Design and Analysis of Avian Habitat Selection Studies
Authors: Battin James , Lawler Joshua J. 
Published: September 2019

Abstract
It has long been suggested that birds select habitat hierarchically, progressing from coarser to finer spatial scales. This hypothesis, in conjunction with the realization that many organisms likely respond to environmental patterns at multiple spatial scales, has led to a large number of avian habitat studies that have attempted to quantify habitat associations at multiple scales. Typically, multiscale habitat selection studies involve the assessment of habitat selection separately at two or more scales. Until recently, these studies have ignored the potential for cross-scale correlations: correlations among habitat variables across scales. If environmental patterns are correlated across the scales being analyzed, researchers using traditional analytical methods may reach erroneous conclusions about the presence or strength of habitat associations at a given scale. We discuss the ways in which cross-scale correlations manifest themselves in two types of habitat selection studies: (1) “constrained” designs that assume a hierarchical ordering of habitat selection decisions, and (2) “unconstrained” designs, which do not assume such a selection process. We demonstrate approaches for quantifying and modeling cross-scale correlations, including a simulation model, a variance decomposition technique, and a hierarchical modeling approach based on classification tree analysis. We conclude that cross-scale correlations have the potential to affect data interpretation in all types of habitat selection studies and that, even with careful attention to experimental design and the application of newly developed statistical techniques, it is likely their effects cannot be eliminated.
Breeding Dispersal In the California Spotted Owl
Authors: Blakesley Jennifer A. , Anderson David R. , Noon Barry R. 
Published: September 2019

Abstract
Spotted Owls (Strix occidentalis) are territorial, generally nonmigratory, and strongly philopatric. Nevertheless, California Spotted Owls (S. o. occidentalis) exhibited breeding dispersal during 7% of interannual observations of banded individuals (n = 54 of 743 occasions). Based on ecological theory and published literature, we made a priori predictions about the factors associated with the probability of breeding dispersal and breeding dispersal distance, and about the consequences of dispersal. Breeding dispersal probability was higher for younger owls, single owls, paired owls that lost their mates, owls at lower quality sites, and owls that failed to reproduce in the year preceding dispersal. Sex had little effect on the probability of breeding dispersal. Dispersal distance was similar for female and male owls (median = 7 km, range = 1–33 km). We found no strong relationships between dispersal distance and any of the conditions that were associated with the probability of breeding dispersal. Dispersal resulted in improved territory quality in 72% of cases. These results indicate that breeding dispersal was condition-dependent and adaptive.
Annual Variation in Numbers of Breeding California Gulls at Mono Lake, California: the Importance of Natal Philopatry and Local and Regional Conditions
Authors: Wrege Peter H. , David Shuford W. , Winkler David W. , Jellison Robert 
Published: September 2019

AbstractThe California Gull (Larus californicus) breeding colony at Mono Lake, California, is the second largest in the world, but its size can fluctuate annually by >45%. We examined six groups of factors that potentially could affect the numbers of pairs nesting each year, including availability of nesting habitat, numbers of potential breeding gulls, environmental conditions along the Pacific coast in the preceding winter, spring conditions at the lake, food availability at the lake, and prior breeding experience. Four variables explained >80% of the variation in the numbers of breeding gulls at Mono Lake between 1987 and 2003: the potential number of four-year-old gulls returning to the lake to breed for the first time, winter coastal conditions associated with the Pacific Decadal Oscillation, density of endemic brine shrimp (Artemia monica) close to the time of egg-laying, and mean temperature in the month before egg-laying. Of the four factors the latter two, which reflect local conditions near the time of egg-laying, had the most profound direct effect on the numbers of breeding gulls. Yearly variation in the snow pack and spring runoff affects brine shrimp numbers through changes in limnological conditions, thus regional climate patterns may indirectly influence gull numbers.
Influence of Habitat Heterogeneity on Distribution, Occupancy Patterns, and Productivity of Breeding Peregrine Falcons in Central West Greenland
Authors: Wightman Catherine S. , Fuller Mark R. 
Published: September 2019

Abstract
We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat.
An Assessment of Bird Habitat Quality Using Population Growth Rates
Authors: Knutson Melinda G. , Hines Randy K. , Powell Larkin A. , Friberg Mary A. , Niemi Gerald J. 
Published: September 2019

Abstract
Survival and reproduction directly affect population growth rate (λ), making λ a fundamental parameter for assessing habitat quality. We used field data, literature review, and a computer simulation to predict annual productivity and λ for several species of landbirds breeding in floodplain and upland forests in the Midwestern United States. We monitored 1735 nests of 27 species; 760 nests were in the uplands and 975 were in the floodplain. Each type of forest habitat (upland and floodplain) was a source habitat for some species. Despite a relatively low proportion of regional forest cover, the majority of species had stable or increasing populations in all or some habitats, including six species of conservation concern. In our search for a simple analog for λ, we found that only adult apparent survival, juvenile survival, and annual productivity were correlated with λ; daily nest survival and relative abundance estimated from point counts were not. Survival and annual productivity are among the most costly demographic parameters to measure and there does not seem to be a low-cost alternative. In addition, our literature search revealed that the demographic parameters needed to model annual productivity and λ were unavailable for several species. More collective effort across North America is needed to fill the gaps in our knowledge of demographic parameters necessary to model both annual productivity and λ. Managers can use habitat-specific predictions of annual productivity to compare habitat quality among species and habitats for purposes of evaluating management plans.