We explored the consequences of male and female explorative and risk-taking behaviors that are components of a behavioral syndrome, as well as basic demographic and physical characteristics of three measures of reproductive performance in Steller's Jays (Cyanocitta stelleri). Older individuals of both sexes performed slightly better in measures of annual reproductive performance. Age was also positively correlated within pairs. In some years, males in better winter body condition performed better, whereas higher-performing females were in worse condition. Because winter body condition was negatively correlated within pairs, males in better condition possibly enabled their mates to invest more in reproduction in a given year, losing more body mass than low-performing females. Overall, variation in individual male and female traits, especially behavioral traits, explained little of the variation in annual reproductive performance. That age was identified as the single most consistent factor, which was correlated within pairs, suggests that experience and compatibility may be more important than inherent individual traits. By contrast, when examining reproductive performance over multiple years, less explorative and risk-averse males produced more offspring over the 3-year study period; the direction of relationships of the four behavioral traits in the syndrome was highly consistent. This suggests an advantage for linkage of these traits in a syndrome, supporting the hypothesis that the combination of traits in behavioral syndromes may be a target for selection.

Much of our understanding of vocal geographic variation in birds is based on the dialects of oscine songbirds that learn their songs. Recent studies have revealed that nonoscine vocal behavior is more complex than previously thought, yet we still have a rudimentary understanding of how vocalizations of suboscine and nonpasserine birds are influenced by genetic and geographic variation. We examined geographic variation in male calls, female calls, and duets of Barred Owls (Strix varia) among 10 locations across the southeastern United States. Recent molecular work revealed two genetically distinct clades of Barred Owl at either end of our transect, with substantial introgression in between. We predicted that calls would vary with genetic distance in a clinal pattern, but that duets and duetting behavior might exhibit dialects similar to that of learned bird song. Discriminant analysis did not reveal any components of vocalizations or vocal behavior that could be used to assign vocalizations to the correct recording location. There were no relationships between any aspect of vocal structure or behavior and geographic distance. Some characteristics of male and female calls and duets varied among locations, but there was no discernible geographic pattern. We suggest that such inconsistent geographic variation in vocalizations is not unexpected for non-song-learning species. The lack of geographic pattern in vocalizations may be due, in part, to high levels of individual variation, recent signal evolution, and local adaptations. We discuss the application of these results to the ontogeny and evolution of complex, coordinated vocal behavior in nonpasserines.

In northern marine habitats, the presence or absence of sea ice results in variability in the distribution of many species and the quality and availability of pelagic winter habitat. To understand the effects of ice on intra- and inter-annual winter site fidelity and movements in a northern sea-duck species, we marked 25 adult Pacific Common Eiders (Somateria mollissima v-nigrum) on their nesting area at Cape Espenberg, Alaska, with satellite transmitters and monitored their movements to their wintering areas in the northern Bering Sea for a 2-year period. We examined changes in winter fidelity in relation to home-range characteristics and ice. Characteristics of polynyas (areas with persistent open water during winter) varied substantially and likely had an effect on the size of winter ranges and movements within polynyas. Movements within polynyas were correlated with changes in weather that affected ice conditions. Ninety-five percent of individuals were found within their 95% utilization distribution (UD) of the previous year, and 90% were found within their 50% UD. Spatial distributions of winter locations between years changed for 32% of the individuals; however, we do not consider these subtle movements biologically significant. Although ice conditions varied between polynyas within and between years, the Common Eiders monitored in our study showed a high degree of fidelity to their winter areas. This observation is counterintuitive, given the requirement that resources are predictable for site fidelity to occur; however, ice may not have been severe enough to restrict access to other resources and, subsequently, force birds to move.

Why individuals use some areas within a home range more than others is poorly understood. One factor that may drive differential use is habitat heterogeneity. We radiotracked 37 male Swainson's Warblers (Limnothlypis swainsonii) at two sites in eastern Arkansas, St. Francis National Forest and White River National Wildlife Refuge. We calculated 95% kernel home ranges and designated areas within and outside of the 55% isopleth as the core area and low-use area for each bird, respectively. We then compared habitat characteristics among used points in core areas, used points in low-use areas, and randomly selected points within home ranges. We predicted that core-area points would have the highest-quality habitat, low-use points would have intermediate-quality habitat, and random points would have the poorest-quality habitat. We found that, in most cases, there were no habitat differences between core-area and low-use points, but used areas differed from randomly selected points. Core-area and low-use points had greater canopy cover, denser and more homogeneous understory, more cane stems and cover, more total understory stems, more leaf litter, and less cover of grasses than random points. We also examined competing hypotheses, but we found that nest locations, home-range centers, and behavior did not explain the location of core areas. The vegetation at random points within core areas suggested that core-area use points might be near more good-quality foraging habitat than noncore points. Our results caution that randomly sampling locations within home ranges where use has not been recorded may not adequately reflect habitat characteristics selected by birds.

The postbreeding period is critical for many forest birds and especially for juveniles, which must learn to forage on their own before the fall migration. During this period, many birds of the boreal forest are found in early-successional stands (ESS), where fruit abundance is typically high. Boreal forest birds may use ESS to exploit fruit or for reasons other than access to fruit, namely to forage along forest edges or simply to transit through clearcuts between patches of mature forest. We tested whether frugivory, edge use, and transit through small (<65 ha) clearcuts between mature-forest patches accounted for bird abundance in ESS in a boreal forest of Quebec during the summers 2007 and 2008. Fifteen of the 33 species captured in ESS were postbreeding frugivores. Removal of all fruits from Sambucus racemosa, a dominant fruiting plant, within 10 m of mist-netting sites reduced the number of frugivores captured by 45% but did not affect nonfrugivores. Numbers of birds captured were independent of distance from mature-forest edges, thus refuting the edge hypothesis, at least in a range of 20–60 m. Mist nets placed parallel to mature-forest edges intercepted more mature-forest birds than mist nets placed perpendicular to edges, as would be expected if mature-forest birds traveled straight through ESS. We conclude that frugivory and transit, but not edge proximity, contribute to the postbreeding abundance of mature-forest birds in boreal early-successional stands.

Cooper's Hawk (Accipiter cooperii) populations breeding in the northern portion of the species' range exhibit variation in morphological traits that conforms to predictions based on differences in prey size, tree stand density, and migratory behavior. We examined genetic structure and gene flow and compared divergence at morphological traits (PST) and genetic markers (FST) to elucidate mechanisms (selection or genetic drift) that promote morphological diversification among Cooper's Hawk populations. Cooper's Hawks appear to conform to the genetic pattern of an east-west divide. Populations in British Columbia are genetically differentiated from north-central populations (Wisconsin, Minnesota, and North Dakota; pairwise microsatellite FST= 0.031-0.050; mitochondrial DNA Φ_ST = 0.177-0.204), which suggests that Cooper's Hawks were restricted to at least two Pleistocene glacial refugia. The strength of the Rocky Mountains—Great Plains area as a barrier to dispersal is further supported by restricted gene-flow rates between British Columbia and other sampled breeding populations. Divergence in morphological traits (PST) was also observed across study areas, but with British Columbia and North Dakota differentiated from Wisconsin and Minnesota, a pattern not predicted on the basis of F_ST and Φ_ST interpopulation estimates. Comparison of PSTand FSTestimates suggests that heterogeneous selection may be acting on Cooper's Hawks in the northern portion of their distribution, which is consistent with hypotheses that variation in prey mass and migratory behavior among populations may be influencing overall body size and wing chord. We were unable to distinguish between the effects of genetic drift and selection on tail length in the study populations.

Nest fate and nest productivity are key demographic parameters for understanding songbird population dynamics, yet little consideration has been paid to assessing and improving the accuracy of these estimates in the field. We considered the magnitude and sources of error in field estimates of nest fate and productivity for 13 species of boreal forest songbirds, the implications of this error when estimating rates of nest survival and population growth, and the utility of common field cues used to assess fate. Using video from 127 nests, we found that observers correctly identified 85% of nest fates but overestimated nest productivity by up to 35%. This resulted in population growth rates being overestimated by 6%. Field estimates were less accurate when nestling age approached the estimated fledge date and when the nest was depredated. Accuracy of field estimates can be improved by focusing on nest condition and the presence of fecal droppings outside the nest. Spending additional time searching for family groups would be prudent when nests are deemed successful on the basis of nestling age alone. Nest predators force fledged one or more nestlings from 14% of nests. The fate of force-fledged young is unknown. Our measures of error declined as increasingly younger force-fledged individuals were considered successful. Resolving this uncertainty would further improve the accuracy of field-based estimates. We encourage the use of video to quantify and improve the accuracy of field estimates and to evaluate the potential for differential bias in error within variables of interest.

Migration is a highly energy-demanding process, and migratory birds store energy at stopover sites along their migration routes to meet these demands. The Veery (Catharus fuscescens) performs one of the longest migrations of all Neotropical migratory landbirds, yet the stopover sites that it uses and their relative importance to migratory success are poorly known. We studied the Veery during two fall migrations (2009 and 2010) in northern Colombia, where we hypothesized that birds would replenish energy reserves after crossing the Caribbean Sea to fuel flights toward their wintering grounds. To determine the relative energetic importance of our study site, we combined estimates of fuel deposition rates, stopover durations, and flight ranges to estimate the percentage of the total migratory distance that could be covered following a stopover. Veeries arrived at our study site with low energy reserves, and recaptured birds increased their body mass at a mean rate of 3.6% of lean body mass day^-1 over an average of 9 days. At departure, birds carried energy reserves equivalent to 34.5% of lean body mass, giving rise to a maximum potential flight range of 2,200 km, thereby allowing them to cover ≤30% of the total fall migration distance, depending on how reserves are used. By showing how a stopover site is used in energetic terms, we highlight the importance of a site in northern Colombia to long-distance Neartic—Neotropic migrants and also introduce a method that contributes to the prioritization of stopover sites across regions and species.

A large number of beak deformities of unknown etiology have recently been reported in Black-capped Chickadees (Poecile atricapillus) and other resident avian species in Alaska. We investigated the potential association between diet and beak deformities. We analyzed carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in whole blood of Black-capped Chickadees captured at three semiurban sites in south-central Alaska. For dietary analysis, we included natural foods (arthropods, seeds, and berries) and anthropogenic items commonly provided in bird feeders (sunflower seeds, peanut butter, and suet). Blood samples from individuals with beak deformities exhibited lower δ¹⁵N values and more variable δ¹³C values than birds with normal beaks. Isotopic values of blood also differed by location for both carbon and nitrogen, but we did not detect a difference in natural dietary items across the three sites. Contributions of individual diet items differed between birds with and without beak deformities, a pattern that likely reflected reduced function of the beak. Affected birds generally consumed fewer arthropods and sunflower seeds and more peanut butter and natural seeds and berries. Although some individuals with beak deformities relied heavily on feeder foods, we did not find evidence of an anthropogenic food source shared by all affected birds. In addition, dietary differences were most pronounced for moderately to severely affected birds, which suggests that these differences are more likely to be a consequence than a cause of deformities.

We describe the range-wide phylogeography of Blackpoll Warblers (Setophaga striata), a migratory passerine with a broad breeding range in North America's boreal forest that encompasses several possible biogeographic barriers but shows no phenotypic geographic variation. We used mitochondrial control-region sequences from 304 individuals in combination with ecological niche models and coalescent simulations to test alternative historical hypotheses about the number of Pleistocene refugial populations and divergences among modern populations. Population pairwise FSTand spatial analyses of molecular variance suggested significant genetic structure among western, eastern, and Newfoundland populations, but no structure among sky-island populations at the southeastern periphery of the breeding range. Inferred gene flow fits a model of isolation-by-distance. Coalescent simulations rejected all multiple-refugia hypotheses in favor of a single refugium. Paleodistribution models and modern migratory pathways suggested that the refugium was located in southeastern North America. In contrast to previous studies that have invoked multiple Pleistocene refugia as the cause of genetic structure in North American bird species, our analyses suggest that geographic structure in Blackpoll Warblers results from isolation-by-distance rather than a history of sundered populations.

We examined baseline and stress-induced changes in plasma corticosterone in relation to body condition and seasonal environmental conditions in three species of cardueline finches wintering in northeastern Oklahoma. Two of these, the Pine Siskin (Spinus pinus) and Purple Finch (Carpodacus purpureus), are irruptive migrants that winter irregularly into Oklahoma, whereas the third, the American Goldfinch (S. tristis), is considered a regular winter resident. Individual turnover of banded birds was high in all three species, which suggests comparable tendencies toward winter transience. Body mass and fat scores of incoming birds increased significantly across the season, peaking in birds captured during midwinter. Baseline corticosterone levels were comparable among species and did not differ seasonally or in relation to daily or weekly temperature fluctuations when the influence of body condition was controlled. By contrast, stress-induced levels of corticosterone secretion varied significantly among species, and changes were correlated with mass- and fat-related indices of body condition. Plasma levels of corticosterone in American Goldfinches and Pine Siskins elevated rapidly during the first 10 min after capture but did not change further, whereas those in Purple Finches continued to rise throughout the 60-min test period. Maximum levels of corticosterone were negatively correlated with residual indices of body condition in American Goldfinches and Pine Siskins, but not in Purple Finches. Interspecific differences in stress-induced elevation of plasma corticosterone and the relationship with body condition are consistent with a possible role of this hormone in modulating foraging activities and, perhaps, local movements of carduelines in response to environmental factors.

Manakins are small suboscine passerines renowned for elaborate courtship displays and pronounced sexual dichromatism. We extracted and identified the carotenoid pigments found in the bright yellow to red feathers of 15 Neotropical manakin species. Rhodoxanthin (4′,5′-didehydro-4,5′-retro-β,β-carotene-3,3′-dione) of a deep red hue was widely found in the plumages of these birds. The 4-keto-carotenoids typically found in red plumages (α-doradexanthin, astaxanthin, canthaxanthin, etc.) were found in only the Flame-crested Manakin (Heterocercus linteatus) and the Red-headed Manakin (Pipra rubrocapilla). Rhodoxanthin was recently identified in the Pin-tailed Manakin (Ilicura militaris). Hudon et al. (2007) suggested that the Pin-tailed Manakin produces rhodoxanthin endogenously from dietary carotenoids, and this suggestion now finds some support in the pigment's wide and specific distribution in manakins. It is possible that this capacity arose in a common ancestor of manakins and cotingas, given that rhodoxanthin also occurs in the feathers of red cotingas (Phoenicircus spp.). Feathers with rhodoxanthin absorbed longer wavelengths of light than those with 4-ketocarotenoids, but not in Pipra, which has species with one or the other type of keto-carotenoids. We found that feathers with rhodoxanthin also contained ε,ε-caroten-3(3′)-ones (e.g., canary-xanthophyll B and the recently described piprixanthin), which are believed to be intermediates along the rhodoxanthin pathway. Manakins thus have the capability to produce a wide range of carotenoid pigments and bright yellow to red colors, on which natural and sexual selection may act.

Long-term bird-banding programs provide knowledge of the demographic rates of avian populations, but we currently lack information on demographic rates of most bird populations in species-rich tropical ecosystems. Banding in tropical regions is typically conducted with protracted or irregular sampling occasions that make the choice of the proper capture—mark—recapture (CMR) model difficult. Here, we address common challenges related to collecting and analyzing data to estimate survival rates of resident Neotropical birds using 20 years of banding efforts in Mexico as a case study. We applied Cormack-Jolly-Seber and Barker models to estimate apparent survival and recapture probabilities of species with sufficient data for survival analyses. We were able to analyze 6 resident species of 136 total species; apparent survival probabilities ranged from 0.30 to 0.77, and recapture probabilities from 0.11 to 0.52. For monitoring programs with existing data collected at continuous, uneven, or irregular intervals, we recommend the application of the Barker model over other models because it was more efficient in the use of available banding data and less often violated CMR assumptions. We recommend that monitoring programs last >10 years and provide additional protocol suggestions for primary and secondary sampling occasions, as well as the number of nets, potential net configurations, and the extent of the spatial scale. These baseline recommendations are likely to foster an increase in our knowledge of avian survival rates in tropical ecosystems, which is imperative for managing tropical bird populations under changing environmental conditions.

Differential reproductive investment between sexes can lead to asymmetric costs of reproduction in birds. Long-lived procellariiform seabirds are single-egg layers with little sexual dimorphism and similar parental investment in incubation and chick rearing. However, sex-specific tasks exist at the beginning of the breeding season, including egg production by females (no courtship feeding by males in this group of species) and nest and mate guarding by males. Costs of reproduction could be evident during critical periods such as the first breeding attempt, because of inexperience in reproductive tasks or a higher proportion of low-quality individuals in young age classes, or both. Little is known about sex-specific costs of reproduction in monomorphic species, in which we expect costs to be similar. We investigated the effects of first reproduction on the subsequent survival of male and female European Storm-Petrels (Hydrobates pelagicus) and found that female survival (0.72; 95% confidence interval [CI]: 0.60–0.82) was lower than that of males (0.85; 95% CI: 0.76–0.89) after first reproduction. However, these differences were not observed in subsequent breeding attempts by experienced females (0.89; 95% CI: 0.86–0.91) and males (0.88; 95% CI: 0.86–0.91), probably because of an experience-related improvement in foraging efficiency, reproductive tasks, or predator avoidance. The effort invested by inexperienced females in the production of a large egg (≤25% of adult body mass) may explain our observed differences in survival.

Since the 1960s, anthropogenic shifts in the timing and distribution of surface-water flows in the Everglades have pushed back the onset of reproduction in Wood Storks (Mycteria americana). Late nesting increases the probability that juveniles leave the colony during the summer rainy season, when water levels are high and prey animals unavailable. We used satellite telemetry to track firstyear survival of 85 Wood Storks from southern Florida over 4 years. We further evaluated survival in relation to hydrologic and physiologic variables, including water depths, surface-water recession rates, May rainfall, use of wetland habitats, sex, total feather mercury, whiteblood-cell counts, and heterophih:lymphocyte ratios for a subset of 71 birds, using a known-fates model in Program MARK. Juveniles that dispersed from the colony during favorable conditions (surface water depths <25 cm) had a first-year survival rate of 0.37 ± 0.06 (SE), compared with 0.15 ± 0.04 for those that dispersed into unfavorable conditions (depths >25 cm). General hydrologie conditions (favorable vs. unfavorable), wetland habitat use, and white-blood-cell counts were the best predictors of monthly survival, and the strongest effects were associated with the first month postdispersal. Our study is the first to show a relationship between temporally fluctuating hydrologic variables and survival of juvenile Wood Storks, highlighting the need to consider the timing of hydrologic manipulations when managing wetlands for birds. We conclude that human-induced changes in the temporal patterns of hydrology may have important consequences for the phenology and, ultimately, the demography of wetland birds.

Males of monogamous species are expected to increase their overall fitness by engaging in extrapair copulations, but the fitness implications of this behavior for females are somewhat less clear. Numerous studies have examined the potential benefits of extrapair mating to females, but the costs of extrapair mating, which may be substantial, are less well studied. Quantifying these costs is critical to understanding the evolution of extrapair mating behavior in females. We examined the costs of extrapair paternity to female Red-backed Fairy-wrens (Malurus melanocephalus) using an 8-year data set that allowed us to examine both short-term and long-term costs. The variability of individual extrapair mating behavior in female Red-backed Fairy-wrens allowed us to compare the parental care, fecundity, and apparent survival of faithful and promiscuous females. We found no effect of the presence of extrapair offspring on the rate at which males provisioned broods. We also found that promiscuous and faithful females did not differ with respect to apparent annual survival and four indices of reproductive success. These findings suggest that there are few or no costs to extrapair mating in females in this population. Low costs, as documented here, may contribute to the evolution of high extrapair paternity rates observed in many species; thus, our results underscore the importance of both costs and benefits in explaining the evolution of extrapair mating behavior in females.

We describe a new species of wren in the genus Thryophilus (Troglodytidae) based on analysis of morphological, vocal, and genetic variation. Individuals of the new species are readily separated in the field or the museum from those of any other wren species, including its closest relatives T. rufalbus and T. nicefori, by a combination of traits including, but not limited to, plumage coloration of the upperparts, the pattern of barring on the wings and tail, overall smaller body size, a richer repertoire of syllable types, shorter trills, and distinctive terminal syllables. The new species is allopatrically distributed in relation to its congeners, being restricted to the dry Cauca River Canyon, a narrow inter-Andean valley enclosed by the Nechí Refuge rainforests and the northern sectors of the Western and Central Andes of Colombia. Individuals or pairs have been found only in remnant patches of dry forest and scrub at 250– 850 m elevation. This newly discovered species is uncommon and threatened because of ongoing transformation of natural habitats in the Cauca River Canyon, and especially because of the planned construction of a major dam in the region; immediate conservation actions are thus imperative.

We describe a new species of barbet in the genus Capito from an outlying ridge of the eastern Andes of Peru. We performed phylogenetic and population genetic analyses of mitochondrial DNA sequences of the new species and C. wallacei and determined that they are reciprocally monophyletic sister species. The new species is diagnosable by plumage and morphology from C. wallacei and is apparently endemic to a small region of montane cloud forest in the southern portion of the Cerros del Sira.