Understanding avian responses to ungulate-induced habitat modification is important because deer populations are increasing across much of temperate Europe and North America. Our experimental study examined whether habitat quality for Blackcaps (Sylvia atricapilla) in young woodland in eastern England was affected by deer, by comparing Blackcap behavior, abundance, and condition between paired plots (half of each pair protected from deer). The vegetation in each pair of plots was the same age. The Blackcap is an ideal model species for testing effects of deer on avian habitat quality because it is dependent on dense understory vegetation and is abundant throughout much of Europe. We compared timing of settlement, abundance, age structure (second-year vs. after-second-year), and phenotypic quality (measured as a body condition index, body mass divided by tarsus length) between experimental and control plots. We used point counts to examine Blackcap distribution, and standardized mist netting to collect demographic and biometric data. Incidence of singing Blackcaps was higher in nonbrowsed than in browsed plots, and singing males were recorded in nonbrowsed plots earlier in the season, indicating earlier and preferential territory establishment. Most Blackcaps, both males and females, were captured in vegetation prior to canopy closure (2–4 years of regrowth). Body condition was superior for male Blackcaps captured in nonbrowsed plots; for second-year males this was most marked in vegetation prior to canopy closure. We conclude that deer browsing in young woodland can alter habitat quality for understory-dependent species, with potential consequences for individual fitness and population productivity beyond the more obvious effects on population density.

Although numerous studies have demonstrated that mature-forest songbirds use successional habitat heavily during the postfledging period, implicit, but yet untested, is the assumption that successional habitat provides high-quality postfledging habitat and promotes juvenile survival. We experimentally tested how access to and use of successional habitat (i.e., regenerating clearcuts) influenced survival and behavior of independent juvenile Ovenbirds (Seiurus aurocapilla). Between 2004 and 2006, we captured and radiotagged 85 Ovenbirds in regenerating clearcuts in southeast Ohio. Radiotagged Ovenbirds were randomly assigned to one of three experimental groups that were released in (1) the original clearcut of capture, (2) a different clearcut of similar age, or (3) a mature forest. Survival of independent juveniles at 52 days was similar among experimental treatments, at 83%. Juvenile survival tended to increase with understory vegetation density and individual energetic condition. Juveniles selected habitat characterized by dense understory vegetation, including large patches of early-successional habitat as well as microhabitats within the mature forest (e.g., riparian thickets, treefall gaps, and forest edges). Ovenbirds released into mature forest habitat traveled farther from their release location after both 7 and 14 days than birds released in clearcut treatments. Although juveniles tended to select dense understory cover during the postfledging period, high juvenile survival did not require large patches of successional habitat.

Although first-category (Type I) songs of some wood-warblers (Parulidae) are structurally stable over time and range, we document a rapid change in the song of a population of Hermit Warblers (Setophaga occidentalis) in northern Oregon. Type I songs on Mount Hood were recorded in 1990 and 1992. When the population was revisited in 2003, the birds in the area sang a different Type I song. The distinctive terminal syllable was absent, the introductory series of repeated syllables had differentiated into two parts, and the first phrase had increased in duration. In 2004, an area within a 20-km radius centered on the original population was systematically searched; from 2004 to 2006, selected areas were searched up to 65 km distant. Five scattered individuals in a limited area were found singing the earlier song 23–28 km to the east, at the periphery of the area dominated by the new song. The differences between the earlier and later songs, which are smaller than differences with neighboring dialects, suggest that the song changed within the current population rather than via displacement by individuals from an adjacent song population. Structural change over time in a Type I song of a wood-warbler over an area larger than a neighborhood has not been previously documented.

Recent research on reproduction in animals has emphasized phenology and prey matching in the long term and on large spatial scales (e.g., linked to global climate change). We studied how individuals within one reproductive cycle and at small spatial scales may try to maximize access to food resources that vary in space and time. Herbivorous mammals are known to track favorable phenological stages of their food plants and move seasonally on the landscape. Whether phenology similarly affects spatial movements of birds on their breeding grounds is largely unknown. We studied postfledging movements of Blue Tits (Cyanistes caeruleus) and Great Tits (Parus major) when the young were escorted by parents during 19 to 43 days posthatching. This was done over 4 years in a 1.6-km² woodland area in Norway in which an elevational gradient (105–266 m) caused a phenological delay in vegetation and peak abundance of caterpillar prey at the higher elevations. Postfledging movements were similar in the two tit species, with a mean distance moved from the nest to the site of observation of 134 m (range: 6–1,036, n = 104). On average, families moved upslope (mean = 4.8 m, range: -23 to 69 m; P = 0.002, n = 104), which suggests that they were able to track environmental phenology. However, most families did not move far from the nest site, possibly because the parents tried to defend a year-round territory and, therefore, could not afford to leave for longer periods.

Studies of habitat selection are often of limited utility because they focus on small geographic areas, fail to examine behavior at multiple scales, or lack an assessment of the fitness consequences of habitat decisions. These limitations can hamper the identification of successful site-specific management strategies, which are urgently needed for severely declining species like Cerulean Warblers (Setophaga cerulea). We assessed how breeding habitat decisions made by Cerulean Warblers at multiple scales, and the subsequent effects of these decisions on nest survival, varied across the Appalachian Mountains. Selection for structural habitat features varied substantially among areas, particularly at the territory scale. Males within the least-forested landscapes selected microhabitat features that reflected more closed-canopy forest conditions, whereas males in highly forested landscapes favored features associated with canopy disturbance. Selection of nest-patch and nest-site attributes by females was more consistent across areas, with females selecting for increased tree size and understory cover and decreased basal area and midstory cover. Floristic preferences were similar across study areas: White Oak (Quercus alba), Cucumber-tree (Magnolia acuminata), and Sugar Maple (Acer saccharum) were preferred as nest trees, whereas red oak species (subgenus Erythrobalanus) and Red Maple (A. rubrum) were avoided. The habitat features that were related to nest survival also varied among study areas, and preferred features were negatively associated with nest survival at one area. Thus, our results indicate that large-scale spatial heterogeneity may influence local habitat-selection behavior and that it may be necessary to articulate site-specific management strategies for Cerulean Warblers.

Closely related species or subspecies can exhibit metabolic differences that reflect site-specific environmental conditions. Whether such differences represent fixed traits or flexible adjustments to local conditions, however, is difficult to predict across taxa. The nominate race of Rock Sandpiper (Calidris ptilocnemis) exhibits the most northerly nonbreeding distribution of any shorebird in the North Pacific, being common during winter in cold, dark locations as far north as upper Cook Inlet, Alaska (61°N). By contrast, the tschuktschorum subspecies migrates to sites ranging from about 59°N to more benign locations as far south as ∼37°N. These distributional extremes exert contrasting energetic demands, and we measured common metabolic parameters in the two subspecies held under identical laboratory conditions to determine whether differences in these parameters are reflected by their nonbreeding life histories. Basal metabolic rate and thermal conductance did not differ between subspecies, and the subspecies had a similar metabolic response to temperatures below their thermoneutral zone. Relatively low thermal conductance values may, however, reflect intrinsic metabolic adaptations to northerly latitudes. In the absence of differences in basic metabolic parameters, the two subspecies' nonbreeding distributions will likely be more strongly influenced by adaptations to regional variation in ecological factors such as prey density, prey quality, and foraging habitat.

Recent evidence suggests that avian population growth rates may be constrained by low postfledging survival. Therefore, quantifying postfledging mortality and understanding the ecological factors that influence it are fundamental for assessing the relative importance of this life-history stage for population growth and identifying the ecological drivers of population dynamics. We radiotracked 110 juvenile Ring Ouzels (Turdus torquatus), a species of high conservation concern in the United Kingdom, to test hypotheses regarding the timing and causes of postfledging mortality and to quantify the timing and magnitude of local movements and dispersal. Juveniles fledged from early-season broods had higher survival during each 4-day period over 116 days postfledging (0.952 ± 0.011 [SE]) than juveniles fledged from late-season broods (0.837 ± 0.021). Most mortality occurred within the first 3 weeks postfledging, and predation by raptors and mammals was the main apparent cause of mortality, accounting for 59% and 27% of deaths, respectively. Juvenile survival decreased at the age of independence from parental care. Juveniles traveled increasing distances from their nests with time after fledging, and those that fledged early in the season dispersed outside the study area at significantly older ages than those that fledged late in the season.

The ability to successfully colonize and persist in diverse environments likely requires broad morphological and behavioral plasticity and adaptability, and this may partly explain why the Peregrine Falcon (Falco peregrinus) exhibits a large range of morphological characteristics across their global distribution. Regional and local differences within Peregrine Falcons were sufficiently variable that ∼75 subspecies have been described; many were subsumed, and currently 19 are generally recognized. We used sequence information from the control region of the mitochondrial genome to test for concordance between genetic structure and representatives of 12 current subspecies and from two areas where subspecies distributions overlap. Haplotypes were broadly shared among subspecies, and all geographic locales shared a widely distributed common haplotype (FalconCR2). Haplotypes were distributed in a star-like phylogeny, consistent with rapid expansion of a recently derived species, with observed genetic patterns congruent with incomplete lineage sorting and/or differential rates of evolution on morphology and neutral genetic characters. Hierarchical analyses of molecular variance did not uncover genetic partitioning at the continental level, despite strong population-level structure (FST = 0.228). Similar analyses found weak partitioning, albeit significant, among subspecies (FCT = 0.138). All reconstructions placed the hierofalcons' (Gyrfalcon [F. rusticolus] and Saker Falcon [F. cherrug]) haplotypes in a well-supported clade either basal or unresolved with respect to the Peregrine Falcon. In addition, haplotypes representing Taita Falcon (F. fasciinucha) were placed within the Peregrine Falcon clade.

Stopover use by migrating shorebirds is affected by patch-level characteristics of habitat, but the relative influence of broad-scale factors is poorly understood. We conducted surveys of ten 10-km-radius landscapes in north-central Oklahoma from 2007 through 2009 to examine the influence of the amount and composition of wetland habitats and surrounding land cover on shorebird use during migration. We used generalized linear modeling and an information-theoretic framework to identify factors that best explained species richness, total abundance, and abundance of four groups of shorebirds classified by breeding status and migration distance. Total abundance and richness both increased with the area of wetland habitat within a landscape, regardless of the composition of semi-natural and developed land cover surrounding wetlands. Abundance of shorebird species with different migration strategies varied in relation to the composition of wetland types within a landscape. The amounts of various permanent and semi-permanent wetlands best explained abundance of resident species. Short-distance migrant abundance was best explained by the amount of permanent lacustrine wetlands. The amounts of temporary and semipermanent floodwater habitats were important predictors for abundance of intermediate- and long-distance migrants, although permanent riverine habitats were also important for intermediate-distance migrants. Shorebird species richness was best explained by the amounts of floodwater habitats and permanent riverine wetlands. Broad-scale studies thus provide important insights on use of stopover habitats by migratory shorebirds. Within this region, conservation of riverine habitats with a large complement of ephemeral habitats is necessary to provide the stopover habitat for migrating shorebirds.

Many migrant songbird species use high-elevation habitats for stopovers in fall throughout North America, but whether these are good migration habitats as indicated by high fueling rates or other measures has not been previously quantified. At high-quality stopover sites, birds can refuel while maintaining their optimal or preferred migration schedules. We used plasma metabolite analysis to estimate fueling rates of four songbird species during the fall migration period over 3 years at two high-elevation (1,200 m above sea level) and two low-elevation (<25 m above sea level) sites in southwestern British Columbia. For three species with more frugivorous diets during fall—the Fox Sparrow (Passerella iliaca), Golden-crowned Sparrow (Zonotrichia atricapilla), and Hermit Thrush (Catharus guttatus)—estimated fattening rates (defined as residual plasma triglyceride levels) were 37–65% higher at high-elevation sites than at low-elevation sites. By contrast, the largely insectivorous and smaller-bodied Orange-crowned Warbler (Oreothlypis celata) had higher estimated fattening rates at low-elevation sites. We found no elevational differences in plasma beta-hydroxybutyrate or glycerol levels except in Hermit Thrushes, which had lower glycerol levels at high elevation. Estimated fattening rates did not differ among the two sparrows and the Hermit Thrush at high-elevation sites, and all three had higher fattening rates than Orange-crowned Warblers. Our data showing strong elevational differences in residual plasma triglyceride levels support the hypothesis that high elevations can be high-quality stopover habitats and, thus, should be considered for protection in songbird management and conservation plans.

Phenological patterns in birds appear to be temperature-dependent in part, and global temperatures are undergoing change. Many studies of bird phenology are conducted at broad temporal but local spatial scales, making it difficult to assess how temperature affects bird migration across landscapes. Recently, networks of “citizen science” volunteers have emerged whose collective efforts may improve phenology studies as biases associated with such efforts are recognized and addressed. We compared mean Rubythroated Hummingbird (Archilochus colubris) first arrival dates from Journey North (2001–2010) with data from the North American Bird Phenology Program (1880–1969). Ruby-throated Hummingbirds arrived earlier in the more recent period throughout the eastern United States; these advances, however, varied by latitude from 11.4 to 18.2 days, with less pronounced changes above 41°N. Warmer winter and spring temperatures in North American breeding grounds were correlated with earlier arrivals at lower latitudes in our recent period. Surprisingly, Ruby-throated Hummingbirds arrived later at high latitudes (42–43°N) during warmer winters and later at both mid- and high latitudes (38–39, 41–44°N) during warmer springs, which perhaps indicates extended migratory stopovers below 40°N during these years. Overall, weather variables predicted arrival dates better in the recent than in the historical period. Our results document spatial variability in how warming temperatures affect hummingbird arrivals and add credence to the hypothesis that spatial differences in arrival patterns at high versus low latitudes could exacerbate asynchrony between some birds and their food resources and modify associated ecosystem services such as pollination and insect pest suppression.

We reconstructed the phylogeographic relationships of the Variable Dwarf-Kingfisher (Ceyx lepidus) using DNA sequence data. Maximum likelihood and Bayesian analysis methods were used to reconstruct trees from a multilocus data set of all 15 named subspecies of the Ceyx lepidus species complex. The concatenated data-set length was 2,471 base pairs and included two mitochondrial genes and two noncoding nuclear introns. Support for the monophyly of C. lepidus was equivocal. We instead found support for a clade including all C. lepidus subspecies plus two endemic Philippine taxa: C. argentatus and C. cyanopectus. Relationships among subspecific taxa were not well resolved, and many nodes were collapsed into polytomies suggesting a rapid and widespread colonization. In situ diversification likely played a role in generating current diversity within four archipelagos: the Philippines, Malukus, Bismarcks, and Solomons. Some biogeographic patterns recovered for the Solomon Islands taxa match those seen in other bird species, such as the close relationship of taxa on Bougainville, Choiseul, and Isabel. By contrast, the sister relationship between populations on Guadalcanal and the New Georgia Group is novel. We discuss species limits and make taxonomic recommendations to treat all 15 subspecies of C. lepidus as species.

Tradeoffs among life-history traits have long provided material for evolutionary studies of life-history strategies but can also have practical implications for assessments of habitat and territory quality in species of conservation concern. Here, we characterize tradeoffs between parental reproductive output and offspring fitness in a closed population of California Spotted Owls (Strix occidentalis occidentalis) using multistratum mark-recapture models and evaluate how potential tradeoffs influenced measures of territory quality. We detected heterogeneity in offspring survival associated with parental reproductive output; individuals that fledged in pairs had a greater probability of surviving than individuals that fledged either as singletons or in triplets, an advantage that was evident in juvenile, subadult, and adult life stages. Thus, the survivorship of offspring that fledged in pairs was high despite costs associated with producing a second fledgling, but the demands of producing a third fledgling came at a cost to offspring survival. Age of recruitment into the territorial population and the future reproductive output of offspring were not related to parental reproductive output in the year of birth. Indices of territory quality based on parental reproductive output were correlated with indices of territory quality based on offspring fitness despite the heterogeneity in offspring fitness associated with parental reproductive output. Our results suggest that ranking territories for conservation planning on the basis of parental reproductive output can be useful in territorial species, but the generality of this finding should be evaluated across a range of life histories.

Grassland bird populations have shown persistent declines over the past four decades in North America. Possible explanations for the declines include decreased winter survival because of habitat deterioration. To address this hypothesis, we evaluated the relationship between habitat structure and winter survival of Vesper Sparrows (Pooecetes gramineus) in Chihuahuan Desert grasslands of northern Mexico. We radiotagged and monitored the survival of 102 individuals during the winters of 2009 and 2010. We obtained visual estimates of vegetation structure and composition at every individual's radiotelemetry location. We used an exponential regression model to estimate daily survival rates and determine the association between habitat structure and survival. We estimated a daily winter survival probability of 99.1% (95% confidence interval: 97.4–99.7%) for Vesper Sparrows in both years. Our survival analysis suggests that habitat structure is an important predictor of winter survival. Average grass height and shrub height were positively related to Vesper Sparrow survival. Our results suggest that grassland bird populations may be negatively affected by poor grassland conditions during the winter and that low winter survival may be an important factor in population declines. Winter habitat conditions in the Chihuahuan Desert grasslands are shaped primarily by grazing and climate, highlighting the need to improve range management, especially in Mexico, as a means to reverse persistent population declines of grassland birds.

The Great Lakes population of Piping Plovers (Charadrius melodus) is federally endangered, numbering between 17 and 71 pairs during 1986–2011. Recovery efforts are diverse, but a major management focus is reduction of predation on eggs and chicks. We evaluated rates and potential causes of mortality for 2,143 chicks from 597 broods at 31 separate breeding sites during 1992–2011. Average daily survival rates of chicks increased from hatch until fledging (∼23 days of age), but this pattern exhibited substantial variation among breeding sites and years, so we included breeding sites and years as random effects in our models. Average (± SE) survival to fledging age was 0.556 ± 0.011. Survival increased with year (1992–2011) and declined with hatching date (28 May–25 July), with seasonal declines becoming more pronounced in recent years. Survival of chicks was reduced by heavy rain (>1 cm) during the first 3 days of life, but <10% of broods were affected. Although site effects were pronounced in the random effects analysis, only one covariate related to nest locations was important: chick survival decreased with proximity of nests to trees. Because broods that hatched earlier in the season had higher survival, management efforts should be focused on finding and protecting nests of early breeding pairs. In addition, because some sites have lower chick survival than others, identifying and ameliorating factors that contribute to low fledging success will likely boost productivity at these sites.

In some species, habitat edges (ecotones) affect nest-site selection and nesting success. Openness, or how visually open a habitat is, has recently been shown to influence grassland bird density and may affect nest-site selection, possibly by reducing the risk of predation on adults, nests, or both. Because edge and openness are correlated, it is possible that effects of openness have been overlooked or inappropriately ascribed to edge effects. We tested the roles of edges and visual openness in nest-site selection and nesting success of two grassland passerines, the Bobolink (Dolichonyx oryzivorus) and Savannah Sparrow (Passerculus sandwichensis), in the Champlain Valley, Vermont. We also evaluated the sensitivity of our results to alternative definitions of edge on our landscape. Bobolink (n = 580) and Savannah Sparrow nests (n = 922) were located on seven hay fields and three pastures from 2002 to 2010. Both species avoided placing nests near edges and in less open habitat compared with expectations based on random placement. When the effects of openness and edge were separated, less open habitats were still avoided, but edge responses were less clear. These results were robust to different definitions of habitat edge. We found no strong relationships between either openness or edges and reproductive success (numbers of eggs and fledglings, percentage of eggs producing fledglings, and nest success), although there may be an edgespecific openness effect on timing of reproduction (clutch completion date). Our results support openness as an important factor in nest-site selection by grassland birds.

Understanding factors that determine sources of nutrients for reproduction is vital to interpreting different life history strategies used among species, within species, and among taxa. We used stable carbon isotope analysis (δ¹³C) to compare the relative use of endogenous and exogenous nutrients during egg synthesis between two species of geese, Canada Geese (Branta canadensis interior) and Lesser Snow Geese (Chen caerulescens caerulescens), nesting on Akimiski Island, Nunavut. We estimated that Canada Geese used 49 ± 1.1% (SE), 61 ± 1.3%, and 51 ± 1.1% endogenous nutrients for albumen, yolk protein, and yolk lipid, respectively. Lesser Snow Geese used significantly less endogenous nutrients during clutch formation, allocating only 25 ± 1.2%, 36 ± 1.5%, and 34 ± 1.7% endogenous nutrients for albumen, yolk protein, and yolk lipid, respectively. Although the proportion of endogenous nutrients allocated to eggs did not vary by year in Canada Geese, proportions varied significantly among years in Snow Geese. We discuss how access to exogenous nutrients appears to be an important factor in determining nutrient allocation strategies during egg production in geese and conclude that, although body size is likely an important ultimate factor in determining overall breeding strategies in birds, proximate factors that influence access to nutrients during egg production appear to be more important in shaping nutrient allocation to egg synthesis. Thus, interactions between physiological and morphological constraints and local environmental conditions can promote the use of flexible strategies in animals that migrate to breed.

We describe a new species of storm-petrel, Oceanites pincoyae (Pincoya Storm-Petrel), from the Puerto Montt and Chacao channel area, Chile. The description is based on 1 specimen collected at sea in Seno Reloncavi on 19 February 2011 and 11 other individuals that were caught, examined, and released. The new taxon's foraging ecology and behavioral habits are unique among the southern Oceanitinae, including “mouse-runs” and repeated diving beneath the surface to retrieve food items. Its distinctive appearance includes bold white ulnar bars, extensive white panels to the underwing, and white to the lower belly and vent. Among species of Oceanites, it is unique in showing white outer vanes to the outer two pairs of rectrices. It further differs from all other storm-petrels in having a distinctive juvenile plumage. Morphometrically it is distinct from Oceanites gracilis gracilis (Elliot's Storm-Petrel) and smaller than O. oceananicus chilensis (the Fuegian form of Wilson's Storm-Petrel), having a shorter tarsus and longer middle toe. There also appear to be differences in the timing of breeding and molt between the new taxon and both O. o. chilensis and O. g. gracilis. We estimate the population size of the new species as ∼3,000 individuals.