Determining how phenotypic traits covary within individuals can offer information on the underlying functional interactions of complex phenotypes and the mechanisms that promote them. We investigated covariation of the white wing patch of the Eurasian Black-billed Magpie (Pica pica) with age, sex, feather wear, spleen size, parasite infection, and testis size to evaluate whether this trait is indicative of individual quality. The white wing area was larger in adults than in second-year individuals, in males and females with larger spleens and lower helminth parasite burdens, and in males with larger testes. In addition, feather wear scores were positively correlated with black melanized areas at the tips of feathers. Our results suggest that wing whiteness reflects age, immune capacity, and feather quality in both sexes and reproductive potential in males. Therefore, this character may play a role in sexual selection by signaling individual quality.

Although interspecific avian brood parasitism usually lowers host productivity, some species lack any defense against parasites. We analyzed the effect of parasite egg removal or nest desertion following a parasitism event on the breeding productivity of the Rufous-collared Sparrow (Zonotrichia capensis), a common host of the Shiny Cowbird (Molothrus bonariensis). The Rufouscollared Sparrow is an effective cowbird host that does not eject parasite eggs. We removed cowbird eggs from nests of Rufouscollared Sparrows to test for differences in hatching, fledging, and nesting success among naturally unparasitized, parasitized, and experimentally unparasitized nests from which we removed the cowbird eggs. We also used simulations to test whether parasite egg removal or nest desertion provide viable strategies to counter the effects of parasitism in this species. Naturally unparasitized nests produced more nestlings and fledglings than parasitized and experimentally unparasitized nests, but there were no differences between parasitized nests and those from which cowbird eggs were removed. Moreover, the overall nesting success was similar for all nest types. Simulation models confirmed these results but also showed that productivity may still increase through parasite egg ejection when the nest predation rate is relaxed only if no cost of parasite egg ejection is assumed. By contrast, nest desertion was not a viable strategy to reduce the effect of parasitism. We suggest that high nest predation could reduce the benefits of antiparasite defenses in the Rufouscollared Sparrow and may help explain the lack of such behavior in this species.

Many birds that are experiencing population declines require extensive tracts of mature forest habitat for breeding. Recent work suggests that at least some may shift their habitat use to early-successional areas after nesting but before migration. I used constant-effort mist netting in regenerating clearcuts (4–8 years postcut) and dense mature-forest understories to assess (1) whether most bird species of mature forests show habitat shifts after breeding; and (2), on the basis of several measures of condition, whether birds using early-successional habitats garnered any benefits or penalties, compared with those that remained in forests. I captured 3,845 individual birds of 46 species at four pairs of sites in mature Allegheny hardwood forests in northwestern Pennsylvania during the postbreeding periods of 2005–2008. Most, but not all, forest birds were captured at higher rates in cuts than in forests, and that pattern persisted through the postbreeding season. Using an information-theoretic approach, I found strong support for a species-habitat interactive effect on both molt progression and body condition as measured by residuals from speciesspecific regression of mass on wing chord. Some, but not all, forest birds appeared to be in better condition when captured in cuts than when in forests. I found no support for a habitat effect on presence of fat or ectoparasites. My result s reveal that habitat choice in the postbreeding season is correlated with physiological condition for a subset of forest birds, which suggests that the maintenance of such early-successional habitats in mature forest may benefit these species.

Range-wide monitoring of shorebirds (Aves: Charadriiformes) suggests that many species are declining. For most species, it is unknown whether distinct population units exist, which makes management and conservation difficult. One shorebird of conservation concern, the Buff-breasted Sandpiper (Tryngites subruficollis), is a New World migrant that breeds at Arctic latitudes in North America and Russia and winters in southeastern South America. We conducted a molecular survey of samples representing each of three migratory regions (breeding, migration, and wintering) using nine polymorphic microsatellite loci and 1.5 kb of highly variable mitochondrial DNA (mtDNA) from the cytochrome b gene and mtDNA control region. We analyzed contemporary population structure, demographic trends, and phylogeographic patterns. Overall, microsatellite and mtDNA analyses revealed that Buff-breasted Sandpipers are panmictic both regionally and at a global scale, with no signal of a recent genetic bottleneck. The mtDNA analyses revealed a pattern of haplotype diversity consistent with an expansion from a single refugium (Tajima's D: -2.27, P < 0.01; Fu's F_s: -30.6, P < 0.0001), after the height of the Wisconsinan glaciation (8,400–45,000 years before present). Overall, our molecular analyses suggest that Buff-breasted Sandpipers should be treated as a single conservation unit, and management efforts for this species should focus on limiting future declines to ensure that genetic viability is maintained.

The recent discovery of a Plasmodium parasite in the endangered Galapagos Penguin (Spheniscus mendiculus) poses a threat to the long-term persistence of this endangered species and, potentially, much of the endemic avifauna of the Galapagos Islands. However, little information is available on the transmission dynamics or pathogenicity of Plasmodium in the Galapagos. We added a simple model of infection to the population model of the Galapagos Penguin devised by Vargas et al. (2007). Two variables (the probability of an individual becoming infected each year, and the increase in annual mortality caused by infection) define the dynamics of the disease component of the model; the stress from El Niño events could affect parasitized individuals in different ways, so three forms of stress-induced relapse are also explored. All models show a high impact due to mortality from infection, and there are large parts of parameter space that have a 0% probability of persistence for the next 100 years. To estimate the mortality that might be associated with Plasmodium infection, a comparison was made between census data from 1998–2009 and model predictions based on the same years. A range of plausible mortality values was determined from the best-fitting models, ranging from 0–5% to 0–10% depending on the type of relapse modeled. Even at these relatively low levels of impact, Plasmodium infection has the potential to drastically reduce the probability of persistence of the Galapagos Penguin population over the next 100 years.

An important step in conservation is to identify whether threatened populations are evolutionarily discrete and significant to the species. A prior mitochondrial DNA (mtDNA) phylogeographic study of the California Gnatcatcher (Polioptila californica) revealed no geographic structure and, thus, did not support the subspecies validity of the threatened coastal California Gnatcatcher (P. c. californica). The U.S. Fish and Wildlife Service concluded that mtDNA data alone were insufficient to test subspecies taxonomy. We sequenced eight nuclear loci to search for historically discrete groupings that might have been missed by the mtDNA study (which we confirmed with new ND2 sequences). Phylogenetic analyses of the nuclear loci revealed no historically significant groupings and a low level of divergence (G_ST = 0.013). Sequence data suggested an older population increase in southern populations, consistent with niche modeling that suggested a northward range expansion following the Last Glacial Maximum (LGM). The signal of population increase was most evident in the mtDNA data, revealing the importance of including loci with short coalescence times. The threatened subspecies inhabits the distinctive Coastal Sage Scrub ecosystem, which might indicate ecological differentiation, but a test of niche divergence was insignificant. The best available genetic, morphological, and ecological data indicate a southward population displacement during the LGM followed by northward range expansion, without the occurrence of significant isolating barriers having led to the existence of evolutionarily discrete subspecies or distinct population segments that would qualify as listable units under the Endangered Species Act.

Amazonia now contains vast areas of secondary forest because of widespread regeneration following timber harvests, yet the value of secondary forest to wildlife remains poorly understood. Secondary forest becomes structurally similar to primary forest after abandonment, and therefore we predicted that avian movement across the interface of primary and secondary forest (hereafter “the interface”) would gradually increase with time since abandonment until recovery to pre-isolation levels. From 1992 to 2011, we captured 2,773 understory birds of 10 foraging guilds along the interface of primary forest fragments and zero- to 30-year-old secondary forest at the Biological Dynamics of Forest Fragments Project near Manaus, Brazil. Our objectives were to understand the differences in land-use history that affect cross-interface movement and to determine how long it takes each guild to recover to pre-isolation capture rates. Across guilds, age of secondary forest within 100 m of the interface was the most important explanatory variable affecting capture rates; rates increased with age of secondary forest for all guilds except non-forest species. Mean recovery to pre-isolation was 26 years (asymmetric SE = 13 years below and 16 years above estimate) after secondary forest abandonment and 9 of 10 guilds recovered within 13 to 34 years. In the slowest guild to recover, terrestrial insectivores, 6 of 12 species were never caught along the interface, and we projected that this guild would recover in ∼60 years. Our recovery estimates quantify the dynamic permeability of the interface and contribute to a better understanding of the value of secondary forests as corridors among primary forest fragments.

Ancient hybridization is difficult to detect and is often surmised from conflicting patterns between phenotypic and genetic data sets that are difficult to explain with alternative hypotheses. Here, a fortuitous macromutation in a microsatellite locus allows an unusually distinctive footprint of ancient introgression to be inferred between two highly divergent bird species that began to speciate in the Late Miocene. A cline of distinctive high-repeat-number (large) alleles at a locus in the Mexican Jay (Aphelocoma wollweberi), which predominantly has low-repeat-number (small) alleles, reaches its highest frequency near the range border with Transvolcanic Jays (A. ultramarina), which are fixed for large alleles, indicating gene flow. The gene flow is not recent, however, because very few of the allelic states are shared between Mexican Jays and Transvolcanic Jays. Ancient gene flow is also more plausible than current gene flow because prior mitochondrial DNA results show no evidence of current dispersal between the ranges of the species, and Mexican Jays with introgressed large alleles are not phenotypically more similar to Transvolcanic Jays, as would be expected with recent hybridization. Although bifurcations in the tree of life are often assumed to belie complex histories of introgression, our results provide some of the clearest evidence that speciation can survive one or multiple bouts of gene flow with no detectable trace in the phenotypes and mtDNA of the constituent species.

Painted Buntings (Passerina ciris) breed in a variety of habitat s across the southern United States; however, a 500-km gap divides the species into eastern and western populations with dramatically different molting schedules. By contrast, the closely related Indigo Bunting (P. cyanea) is syntopic with Painted Buntings, but its range includes the 500-km gap. To date, no well-supported hypothesis explains the gap in the range of Painted Buntings. We used MaxEnt to describe ecological niches of both species and performed comparative analyses of model results to evaluate niche similarity between the two Painted Bunting breeding populations and the range gap. All present-day niche models for both species predicted a single contiguous breeding range, which suggests that the gap in the Painted Bunting range is not bioclimatic in origin. Comparative analyses of the three different environments suggest little bioclimatic divergence. Distribution models during the Last Glacial Maximum suggest that Painted Buntings likely bred as far north as ∼28°N latitude, with two disjunct populations in what are now Florida and northern Mexico. Although alternatives exist, the most parsimonious explanation is that the Gulf of Mexico serves as a migratory divide and there are fitness costs to birds attempting to fly around or over the Gulf to reach their molting or wintering grounds. This was a primary factor contributing to the origin of the current allopatric breeding distribution. Historical distribution models imply that the species may not have filled the 500-km gap as their breeding range expanded northward; divergent molting schedules may reinforce the existing range disjunction.

We studied patterns of geographic variation in structural size and genetic characteristics of white-cheeked geese inhabiting coastal areas of Hudson Bay, Canada, from northern Manitoba to southern Nunavut to determine the degree of morphological and spatial overlap, if any, between Cackling Geese (Branta hutchinsii) and Canada Geese (B. canadensis) in this region. Most Canada Geese occurred in sub-Arctic habitats south of 59°N latitude, and most Cackling Geese occurred in Arctic habitats north of 60°N, but the two species overlapped in a narrow zone between 59°N and 60°N latitude that coincided with the ecotone between sub-Arctic and Arctic ecozones. Mismatches between morphological and genetic characteristics of some individual females suggested that introgression had occurred in this area, and contrasting patterns in the nuclear and mitochondrial DNA (mtDNA) were consistent with female natal philopatry and male-biased dispersal. Evidence of introgression in the nuclear genome was geographically more widespread than evidence of introgression in the mtDNA genome. We suggest that the persistence of Canada Goose mtDNA in phenotypic Cackling Geese is a result of historical hybridization events that occurred when the Arctic—sub-Arctic ecotone was located farther north during a warmer climatic period. Despite evidence of introgression, most birds that we sampled appeared to belong to one or the other parental species, on the basis of their consistent identification using morphological, mtDNA, and nuclear DNA characteristics. We suggest that the area of overlap represents a tension zone between Canada Geese and Cackling Geese that is maintained by behavioral and ecological factors that limit effective dispersal.

Substantial offspring mortality can occur during the postfledging period of birds, but few postfledging survival studies have been conducted within the context of habitat suitability. We conducted a 2-year radiotelemetry study of Spotted Towhee (Pipilo maculatus) reproductive success and fledgling survival in a 24-ha forested park in a residential area of Lake Oswego, Oregon. In corroboration of previous research on this species, we found (1) that Spotted Towhees nested closer to the edge between the park and residential neighborhoods than expected by chance, and (2) that pairs nesting near edges produced the largest and most offspring. However, fates were reversed during the postfledging period. Thirty-six of 52 fledglings survived the 27-day tracking period, and although fledglings were more likely to be found near edges than in the interior, fledglings near edges had a far higher probability of dying. All deaths were from predation, and at least 11 of 16 predation events were attributable to Domestic Cats (Felis catus) and Western Screech-Owls (Megascops kennicottii). A stochastic model that incorporated probability of nest success, nestling production from successful nests, and fledgling survival showed that the number of independent offspring produced per nest was greatest in the park interior. Heavy use of, and apparent preference for, edge by nesting Spotted Towhees, coupled with high fledgling mortality near edges, created a severe ecological trap that was not apparent until the final stage of parental care. Hence, failure to document offspring survival in the late stages of reproduction may lead to incorrect assessment of habitat suitability and poor management decisions.

Grassland birds are often affected negatively by habitat fragmentation. Outcomes include greater nest predation and brood parasitism, decreased colonization rates of small, isolated patches, and greater nest density in remnant core habitats. These effects have been well documented in the Midwest, but little is known about fragmentation and edge effects on grassland birds in the fragmented agricultural fields within the forested landscapes of the northeastern United States. From 2002 to 2010, we assessed how edges and edge types affected nest-site location and daily nest survival (DNS) of Savannah Sparrows (Passerculus sandwichensis) and Bobolinks (Dolichonyx oryzivorus) breeding in 11 fields (range: 13.2–38.3 ha; mean = 21.1 ha) within a large agricultural region of Vermont. Mean (± SD) distance to edge was 80.3 ± 39.6 m for Savannah Sparrows (n = 995) and 94.5 ± 56.5 m for Bobolinks (n = 652). Both species nested significantly less than expected within 50 m of the edge. For Savannah Sparrows nesting within 50 m of the edge, DNS increased with increased distance from the edge. Birds initiating nests later in the season nested closer to edges, but renests were farther from edges than first nests. Distance to edge had no detectable consequence for Bobolink nest success. Both species used portions of fields near hedgerows less than expected but used wetland, forest, agricultural, road, and developed edges in proportion to availability. For both species, DNS did not vary among edge types. Although edges were used less than expected, nesting near edges had only minor consequences for nest success.

Proliferation of wind energy across the Great Plains of the United States has the potential to negatively affect many grassland birds through displacement, avoidance, or changes in nesting ecology. This is troublesome because grassland birds have had the highest average annual rate of decline over the past several decades. We studied the potential indirect effects of wind turbines on nesting success in Dickcissels (Spiza americana) at a utility-scale wind farm in north-central Texas in 2010 and 2011. We monitored 195 nests and found that proximity to a wind turbine did not affect nest density or nest-site characteristics. We used an information-theoretic approach with logistic exposure modeling to identify the most likely models of nest fate. Nest initiation day and distance to wind turbine were the most important predictors of nest success. Proximity to a wind turbine did not reduce nest success. Furthermore, the daily survival rates at our site were within the range documented for Dickcissels at other sites without wind-energy developments. For the monitored nests, snake predation was the greatest source of nest failure and depredated nests were closer to woodland edges than to wind turbines. This may be because wind turbines were farther away from wooded edges. On the other hand, we cannot rule out the possibility that wind-energy development influenced predator behavior and activity, and this may warrant additional investigation. We recommend further research into the breeding ecology of a diverse selection of grassland species to fully assess the indirect effects of wind-energy development on grassland birds.

Although it has long been recognized that many tropical birds do not share the same narrow breeding periods as temperate birds, conventional thinking considers tropical breeding seasons to be discrete periods generally governed by rainfall seasonality. We used a database of >31,000 captures of 104 species collected over 17 years in rainforest near Manaus, Brazil (2.5'S), to examine timing of breeding. The proportion of individuals with active incubation patches peaked at 7% in the dry season, from October through December. The peak was about twice as high as the lowest rate, in the late wet season (April—June). From 9 to 15 families and >20 species bred in every month. Many taxa did not conform to the general pattern, instead peaking in the wet season (e.g., Galbulidae, Sclerurinae, Grallariidae, and Formicariidae). Most well-sampled species, even those with strong seasonal peaks, bred at almost any time of year, a pattern also shown by some individual birds that were captured multiple times in breeding condition. Among the 10 species with >50 incubation patches, all bred in at least 9 months, and 7 bred in 11–12 months. Earlier results from the same data set showed extremely protracted molts that regularly overlapped breeding. Collectively, molt and breeding data suggest that the annual cycle of some equatorial birds, particularly suboscines, differs fundamentally from that of temperate species, with much less fixed timing of breeding.

Fluctuating asymmetry has been suggested to be a phenotypic marker of developmental stability and is often seen as an indicator of overall quality. However, its role in sexual selection has been debated. To determine the potential role of black wingtip asymmetry in sexual selection in Black-legged Kittiwakes (Rissa tridactyla), we investigated whether symmetry was correlated with reproductive success and integument coloration, a trait probably sexually selected in this species. We found that, in males, asymmetry was associated with low clutch size and brood size but was independent of fledging success, which suggests that wingtip symmetry may reflect fertility in males. Asymmetry of black wingtip was also associated with duller integument, which emphasizes the potential importance of integument color in indicating individual quality. Further studies are needed to determine whether Black-legged Kittiwakes can discriminate between asymmetric and symmetric birds and use it as a cue in mate choice or intrasexual competition.