I studied the recurrence of similar plumage-pattern elements in distantly related taxa across class Aves and examined whether such pattern elements are associated with morphological features, such as body size and anterior emphasis, and with habitat type and age class in selected examples. The identification of recurrent plumage-pattern elements across a wide array of taxa can be interpreted as evidence for parallel evolution and thus for shared developmental pathways. Developmental constraint, therefore, may serve to both generate and delimit the diversity of avian plumage patterns, which are subsequently presented to selection. By examining over 8300 examples of avian plumages mostly from the literature, I derived a plumage-pattern trajectory that can be used as a theoretical model to identify associated morphological trends within various taxonomic contexts of comparison. When comparing species within a clade, as body size increases, plumage pattern often shifts along a trajectory, from countershading through streaks, bars, uniform or bold black and white patches, to reverse countershading. Moreover, the trajectory is recursive at various taxonomic levels. The recursive nature of the trajectory, in which morphological and pattern elements recur in modified configurations, has perhaps contributed to an underestimate of parallel evolution in birds. I assert that a recognition of morphological recursion enables one to predict evolutionary trends in a hypothetical spectrum of potential form and plumage pattern and thus serves to define both the limits and possibilities of avian morphospace.

Characteristics of successful vs. unsuccessful nest sites are likely to vary over time and space in response to habitat changes. I used the Thorn-tailed Rayadito (Aphrastura spinicauda, Furnariidae), a cavity-nesting species endemic to the temperate rainforest of southern South America, as a model species to determine if territory use and nest-tree selection, and associated consequences for fitness, varied spatially in response to human-driven habitat changes. I established two 10 ha plots in each of three forest habitats that differed in structure and isolation: connected old-growth forest, connected logged forest, and isolated logged fragments. Characteristics of trees used for nesting varied among forest types, but nest success did not. In connected forests (old-growth and logged forest), snags were used more often than expected based on their availability. Nest survival models identified type of tree (snag vs. live tree) and epiphyte cover of trees as the variables with the strongest effects on daily nest survival. Nests in snags and with less epiphyte cover were more successful than nests in live trees. These results support an adaptive nest-site choice in this species. In isolated logged fragments, use of nest trees was proportional to availability, with smaller trees and different tree species used for nesting, suggesting behavioral plasticity in nest-site selection. Territories were similar among forest types and were characterized by a dense understory and more large trees and snags than unused areas. This study provides evidence for consistent territory use but spatially variable nest-tree selection in response to ecological gradients produced by human activities.

Birds in which only one sex incubates the eggs are often faced with a direct conflict between foraging to meet metabolic needs and incubation. Knowledge of environmental and ecological factors that shape life-history strategies of incubation is limited. We used continuous videography to make precise measurements of female Greater Sage-Grouse (Centrocercus urophasianus) incubation constancy (percentage of time spent at the nest in a 24-hour period) and recess duration. We used an information-theoretic approach to evaluate incubation patterns in relation to grouse age, timing of incubation, raven abundance, microhabitat, weather, and food availability. Overall, sage-grouse females showed an incubation constancy of 96% and a distinctive bimodal distribution of brief incubation recesses that peaked at sunset and 30 min prior to sunrise. Grouse typically returned to their nests during low light conditions. Incubation constancy of yearlings was lower than that of adults, particularly in the later stages of incubation. Yearlings spent more time away from nests later in the morning and earlier in the evening compared to adults. Video images revealed that nearly all predation events by Common Ravens (Corvus corax), the most frequently recorded predator at sage-grouse nests, took place during mornings and evenings after sunrise and before sunset, respectively. These were the times of the day when sage-grouse typically returned from incubation recesses. Recess duration was negatively related to raven abundance. We found evidence that incubation constancy increased with greater visual obstruction, usually from vegetation, of nests. An understanding of how incubation patterns relate to environmental factors will help managers make decisions aimed at increasing productivity through successful incubation.

The populations of many species are declining worldwide, and conservation efforts struggle to keep pace with extinction rates. Conservation biologists commonly employ strategies such as translocation and reintroduction, which move individuals of endangered species from one part of their range to another. Because individuals from endangered populations are nonexpendable, identifying any potential barriers to the establishment of viable populations prior to release of individuals should be a priority. This study evaluates the potential for learned communication signals to constrain conservation strategies such as reintroduction in an endangered species, the Thick-billed Parrot (Rhynchopsitta pachyrhyncha). We conducted vocal surveys at three geographically distinct breeding populations in the Sierra Madre Occidental of Chihuahua, Mexico. Acoustic analyses utilizing both spectrogram cross-correlations and parameter measurements from spectrograms revealed no significant differences among the three sites in two common call types. Calls did vary among individuals within a site. The apparent lack of significant geographic variation across sampled sites suggests that differences in learned communication signals are unlikely to pose a barrier to the integration of translocated individuals from different populations into newly established populations.

Individual recognition, the ability to correctly identify an individual, relies upon individual distinctiveness in a trait being used to determine identity. However, if such distinctiveness is not stable over time, its usefulness is limited. The purpose of this study was to assess individual distinctiveness in the begging calls of female White-throated Magpie-Jays (Calocitta formosa) recorded over different time periods. Such food solicitation calls could be selected to encode caller identity if multiple individuals within a group or neighborhood produce them. On average, a discriminant function analysis of 29 call parameters correctly assigned 51% of each female's calls to the appropriate female, suggesting that begging calls are individually distinctive. However, females that were recorded on many days were more likely to have their calls incorrectly assigned than were females recorded on one or a few days. On a short time scale, females produce calls consistently, but calls vary over longer time scales, causing a significant decrease in assignment accuracy. Such decay in accuracy raises questions about reported individual distinctiveness in other species that have not been sampled over longer time periods or on multiple occasions. In White-throated Magpie-Jays, floater males looking for fertile females, or group members determining whom to feed could benefit from individuality in begging, but they may need to integrate identity information over multiple calls in order to correctly determine sender identity.

Many aspects of migration have been studied extensively, but little is known of how environmental conditions influence the behaviors displayed by migrants. Field studies suggest that such environmental factors as atmospheric conditions, nocturnal illumination, and food availability can affect migratory activity. We used 24 hr locomotor activity records and specific behaviors displayed by captive migrants to determine how nocturnal illumination and food restriction altered the migratory behavior of Gambel's White-crowned Sparrows (Zonotrichia leucophrys gambelii). Our results indicated that nocturnal locomotor activity was enhanced with increased nocturnal illumination at the source from 0 to 9 lux, even though the intensity of illumination that reached the birds remained <1 lux. Food deprivation had little effect on migratory restlessness per se, but resulted in increased locomotor activity during daylight hours and behaviors associated with attempts to escape from the cage. Thus, we suggest that migrants respond to variations in environmental conditions by altering both day and nighttime behaviors. Plasticity of behavior would allow free-living migrants to respond quickly to changes in the environment, thus enhancing the likelihood of successfully reaching their destinations.

We used radio-telemetry to examine fine-scale movement patterns of Wilson's Warblers (Wilsonia pusilla) at a stopover site on the lower Colorado River during spring migration in 2005 and 2006. The overall movements of Wilson's Warblers were restricted to small, localized areas, with an average linear displacement of only 332 m. Warblers exhibited exploratory behavior characterized by fast, long-distance, directed linear movements during the first and second day after presumed arrival at the stopover site. However, exploration was limited within the overall landscape (<2 km diameter), suggesting a cost to extended exploration. As individuals gained more information about the distribution of resources at the stopover site through exploratory behavior and direct sampling of the habitat, movements became more aggregated within a localized area, suggesting that Wilson's Warblers settled within a microsite at the stopover site to replenish fuel supplies. The overall movement patterns exhibited by warblers during stopover were influenced by the age of the individual and changes in resources, both within a season and between years. Movement patterns of Wilson's Warblers documented during this study provide essential information about the temporal distribution of a warbler's locations within a stopover site, indicating how birds search for and acquire food resources throughout their stopover.

Long-term datasets reveal declines in many populations of landbird migrants, with declines especially evident in shrub-nesting species. Moreover, transitional shrub-dominated habitats are becoming scarce, reducing breeding habitat for these species. Because migrants often occupy habitats en route similar to those used in the breeding season, the persistence of shrub-dominated habitats may be especially critical for these species during passage. Because little is known about migrant-habitat relationships, especially at inland, unforested stopover sites, we compared the importance of forested and upland shrub-dominated habitat to spring migrating landbirds by comparing: (1) temporal and habitat-related variation in resource abundance, and (2) migrant use of forested vs. shrub-dominated habitat during stopover. We collected data on bird-habitat relationships and invertebrate abundance from both habitats at two sites in or near Lackawanna State Park, Lackawanna County, Pennsylvania. We captured and counted more short-distance and long-distance migrants in shrub habitat (256 birds per 1000 mist-net hours and seven birds per 100 m of survey transect) than in forested habitat (67 birds per 1000 mist-net hours and three birds per 100 m of transect), and shrub habitat contained a somewhat greater diversity of migrants (H′ = 4.0 vs. 3.9). We also measured greater flying invertebrate biomass in shrub vs. forested habitat, although there was no difference in flightless invertebrate biomass between the two habitats. Our results support the hypothesis that migrant habitat use reflects spatial differences in resource abundance and indicate that shrub-dominated habitats may be important stopover habitat for landbird migrants.

Male secondary sexual characters can provide females with information regarding the fertilizing capacity of a male's sperm. In some fishes and birds, intense nuptial coloration is correlated with male fertilizing capacity, but no mechanistic link between coloration and sperm quality has been established. One plausible mechanism is that carotenoid pigments, which color skin and feathers in many animals, are present in seminal fluid and serve as antioxidant protectors of sperm. We used high-performance liquid chromatography (HPLC) to analyze sperm samples from four species of Australian fairy-wren (Malurus) and detected low concentrations (<1 μg ml⁻¹) of carotenoids in some samples. Xanthophyll carotenoids (including lutein and zeaxanthin), which are typically dietary in origin, were present in the seminal fluid of Superb (M. cyaneus) and Splendid (M. splendens) Fairy-Wrens. In contrast, red ketocarotenoids (including astaxanthin and canthaxanthin), which are likely metabolically derived from dietary precursors, were present in the seminal fluid of Red-backed Fairy-Wrens (M. melanocephalus). This work is the first to report carotenoids in avian seminal fluid and suggests that, although carotenoids are at low levels and thus may have limited antioxidant activity, there may be biological variability in avian semen carotenoids on which selection could act.

Fitness in a hybrid zone is determined both by the reproductive success and the survival of phenotypes. The hybrid zone of Northern Flickers (Colaptes auratus), a common woodpecker, is one of the largest and most well-known hybrid zones in North America. Bounded-hybrid superiority, the most widely accepted hypothesis for the persistence of the zone, suggests hybrids should have equal or higher reproduction or survival than parental types in the zone, but the latter life history trait has never been examined. We analyzed the apparent survival of 1117 flickers over nine years using capture-recapture models and found no evidence that the phenotypic hybrid index influenced survival. Instead, annual adult apparent survival was best modeled according to large-scale weather patterns such as the North Atlantic Oscillation (NAO). During warm phases of the NAO, adult flickers had lower survival compared to cooler phases of NAO. There was no evidence that phenotype influenced the local recruitment of yearling flickers to the study area and no effect of NAO on this relationship. These results suggest survival in the flicker hybrid zone is largely influenced by annually variable weather patterns and that if there are differences in survival according to phenotype, they are extremely small for the flicker hybrid zone in the north.

Seabirds may be particularly vulnerable to neonatal food restriction because their nestling periods tend to be long and parents may not increase foraging effort during times of prey shortage. We performed a captive study of Rhinoceros Auklet (Cerorhinca monocerata) nestlings to identify adaptations for coping with food shortages, as well as possible consequences of early diet restriction on subadult morphology. We tested effects of a ~50% caloric restriction on Rhinoceros Auklet morphological allocation and levels of the stress hormone corticosterone. Rhinoceros Auklets were reared in captivity and provisioned either ~441 kJ per day or ~227 kJ per day of high-quality forage fish until fledging (n = 13 for both treatment groups). Food-restricted Rhinoceros Auklets allocated energy heavily toward skeletal growth at the expense of mass reserves, resulting in fledglings that were proportioned very differently compared to nonrestricted birds—i.e., at 42 days of age, all birds had approximately the same wing length despite a 95 g difference in mass. Nestlings with restricted diets exhibited low plasma concentrations of corticosterone over the course of the experiment, although baseline levels were consistently higher than those of nestlings not restricted in diet. At 11 months of age, birds whose diets had been restricted were still ~50 g lighter than those whose diets had not been. The former had smaller tarsi, marginally smaller culmens, but similar-sized manus. Our results suggest Rhinoceros Auklets use both morphological allocation and adrenocortical suppression to cope with energy shortages in the nest.

The grackles (Quiscalus spp.), together with their sister genus Euphagus, compose a clade within the New World blackbirds (Icteridae). We used gene sequences of cytochrome b and NADH dehydrogenase subunit 2 (ND2) to reconstruct relationships within this group. A primary concern was determining the phylogenetic position and genetic distinctiveness of the extinct Slender-billed Grackle (Q. palustris)—a poorly known endemic of the Lerma Basin and the ancient lakes of the Valley of Mexico, last collected and recorded in 1910—and of the Nicaraguan Grackle (Q. nicaraguensis), which is likewise unusual among grackles for its restricted geographic range. Our analysis differs from previous efforts by inclusion of these taxa along with all other recognized grackle species, intraspecific sampling of Greater Antillean (Q. niger), Carib (Q. lugubris), and Great-tailed (Q. mexicanus) Grackles, and inclusion of additional sequence data. The recovered phylogeny reveals Slender-billed Grackle to be most closely related to one of two major haplotype clades of Great-tailed Grackle, the other being sister to Boat-tailed Grackle (Q. major). Nicaraguan Grackle appears sister to Carib Grackle (Q. lugubris). We discuss the implications of these and other relationships in the genus for species limits and biogeography.

Many avian species from the temperate zone show low levels of genetic diversity when compared with species from the tropics, although there are some interesting exceptions, and species whose ranges occur across the temperate–tropical boundary could have characteristics of either or both zones. The distribution of the Streak-backed Oriole (Icterus pustulatus) extends from northwestern Sonora in Mexico south along the Pacific coast to Costa Rica. In addition, there is a population on the Tres Marías Islands. Northern populations are migratory and dichromatic (sexes different), whereas southern populations are nonmigratory and monochromatic (sexes alike). We sequenced mtDNA (control region domain I) from 102 individuals across the range of this species. Maximum parsimony and maximum likelihood analyses did not support the existence of multiple species within Icterus pustulatus based on mtDNA. However, populations from the Tres Marías Islands seem to have been isolated long enough to have fixed differences from populations on the mainland. The species complex shows an uncommon phylogeographic pattern, with shallow haplotype trees and weak geographic structure, suggesting that it has undergone recent population expansion. We recommend that the insular populations be considered a separate species, Icterus graysonii, given the fixed differences from mainland birds in multiple characteristics, including mtDNA and plumage patterns.

In an effort to provide wildlife habitat and link blocks of forested habitat, coastal forested buffer strips in the Pacific Northwest are managed to mitigate effects of fragmentation that result from timber harvesting adjacent to a coastline. We examined the effect of coastal forest buffer strip width on avian nest survival on Prince of Wales Island, Alaska, in 2003 and 2004. We established nest monitoring plots in two buffer width treatments, narrow (<250 m, n = 4) and wide (>350 m, n = 3), and monitored a total of 142 nests of six species: the Pacific-slope Flycatcher (Empidonax difficilis), Chestnut-backed Chickadee (Poecile rufescens), Winter Wren (Troglodytes troglodytes), Swainson's Thrush (Catharus ustulatus), Hermit Thrush (Catharus guttatus), and Varied Thrush (Ixoreus naevius). We modeled and compared the daily survival rate (DSR) of each species in both buffer width treatments. Point estimates for DSRs were slightly higher within wide buffers, but confidence intervals overlapped for all species. Overall, Pacific-slope Flycatchers had the highest nest success (87%) and Varied Thrushes had the lowest (22%). In addition, we used an information-theoretic approach to examine support for hypotheses concerning the effects of edge on nest survival of the Hermit Thrush, the only species for which we had sufficient data. Hermit Thrush nest survival was negatively affected by proximity to the coastline. Predators associated with the productive intertidal zone likely increase the predation risk of Hermit Thrush nests located near the coast.

We tested statistical models developed to predict abundances of grassland birds in the Prairie Hardwood Transition Bird Conservation Region of the upper midwestern United States. Roadside surveys were used to estimate relative abundances of grassland birds in 800 ha areas in the Iowa, Minnesota, and Wisconsin portions of the region in 2003–2005. We then compared observed abundances with predicted abundances from spatial hierarchical models for seven species. Spearman's rho statistic for rank correlations suggested that observed abundances were positively correlated with predicted abundances for all species (r_s = 0.21–0.60) except the Henslow's Sparrow (Ammodramus henslowii; r_s = 0.01). Observed abundances also were positively correlated with percent grassland in an area, and rank correlation values were similar to those obtained from the predictive models. Model accuracy was positively related to species' abundance and niche breadth. Our accuracy assessment suggested that the spatial hierarchical models would have limited use in guiding management at a regional scale; a measure of habitat quantity performed equally as well as the models at predicting observed abundances. Future efforts to model grassland bird abundances would be improved by more accurate information on the distribution of grasslands in the region, more detailed information on grassland composition and structure, and a better understanding of the biological significance of environmental variables for grassland bird populations.

We investigated molted-feather persistence and aging in a sub-Arctic environment by placing marked feathers at historical Gyrfalcon (Falco rusticolus) nesting areas and returning a year later to collect and inspect remaining feathers. After one year, only 14% of marked feathers remained and were collected during primary searches; small, body feathers were significantly less likely to persist than large or flight feathers. No differences in trends were detected between feathers from perch and below-nest locations. All recovered feathers displayed at least one of three signs of aging (matted and separated barbs, fungal growth, or algal growth) that reliably distinguished them from fresh feathers. We show that collection efforts should focus on small, body feathers to ensure that collected feathers are freshly molted and suggest feather persistence and aging be directly addressed in other studies using feathers for noninvasive genetic sampling. Doing so should reduce potential genotyping and data interpretation errors, help meet capture-mark-recapture assumptions, and increase confidence in results.

To assess the value of molted feathers as a noninvasive source of DNA for genetic studies of Northern Goshawks (Accipiter gentilis), we isolated and quantified DNA from molted feathers and compared yields across five feather types. We also compared PCR success across the same five feather types using five microsatellite genetic markers of varying size. In addition, we compared DNA yields from a commonly used extraction method versus one we modified to increase DNA yield. Results indicated molted feathers provided on average 24 ng μl⁻¹ of DNA, which is a relatively high DNA yield compared to other noninvasive tissue sources. Tail feathers yielded significantly more DNA than primary, secondary, and smaller feathers, yet all feather sizes produced equally high rates of PCR success. Although our modified extraction method increased the time required for processing feathers, it resulted in significantly higher yields of DNA as compared to the unmodified protocol.

The presence of blue-green egg pigmentation has puzzled naturalists for more than 100 years. One hypothesis on the function of this pigmentation proposes that blue-green egg chroma signals female quality and that males respond to this signal by increased provisioning to presumably higher-quality clutches. The hypothesized mechanism is that blue-green egg color signals female antioxidant capacity, because the eggshell pigment responsible for blue-green coloration, biliverdin, has antioxidant properties in the mother. Our study is the first to examine this mechanism, which is critical to this hypothesis. We found that female Gray Catbirds with higher total antioxidant capacity laid eggs with higher blue-green chroma. In addition, we found that males provided more care to nestlings from clutches with higher average blue-green egg chroma. This shows an intriguing potential link between female antioxidant capacity and blue-green egg chroma. Interpreting the variation in females' antioxidant capacity will require a better understanding of the relative importance of dietary intake of antioxidants, oxidative stress, and the cost of depositing biliverdin into eggs.

We hypothesized that the foraging behavior of urban birds would be less sensitive to variation in the cost of predation than that of nonurban bird species. We predicted that food-patch utilization by House Sparrows (Passer domesticus), a widespread human commensal, would be less sensitive to variation in predation risk than that of Spanish Sparrows (P. hispaniolensis), its nonurban counterpart. We applied the giving-up density (GUD) method to quantify patch use behavior of the two species with respect to distance from shelter. Our results indicated that Spanish Sparrows perceived a steep gradient of increased predation cost with increasing distance from shelter, while House Sparrows seemed indifferent to distance from shelter. These results support the hypothesis that the cost of predation has less effect on the foraging behavior of urban than nonurban birds, although alternative explanations include differences between species in the degree of neophobia, or variations in their ability to assess predation risk.

In forests, high-severity burn patches—wherein most or all of the trees are killed by fire—often occur within a mosaic of low- and moderate-severity effects. Although there have been several studies of postfire salvage-logging effects on bird species, there have been few studies of effects on bird species associated with high-severity patches in forests that have otherwise burned at lower severities. From 2004 to 2006, we investigated the foraging presence or absence of three woodpecker species, the Black-backed (Picoides arcticus), Hairy (P. villosus), and White-headed (P. albolarvatus) Woodpeckers, within four different forest habitat conditions in Sierra Nevada conifer forests: unburned; moderate-severity and unlogged; high-severity and unlogged; and high-severity and logged. We found Black-backed Woodpecker foraging was restricted to unlogged high-severity patches. Hairy Woodpeckers foraged most in unlogged high-severity patches, and White-headed Woodpeckers showed no significant difference in presence among conditions. These results suggest that unlogged, high-severity forest is important habitat for the Black-backed and Hairy Woodpeckers.

Many birds ingest small stones to aid in the grinding up of coarse food items in the diet. However, small stones are also found in the stomachs of species with diets consisting of soft food items, and may serve to mechanically remove parasites attached to the stomach wall. We sampled Double-crested Cormorants (Phalacrocorax auritus) at two sites to examine whether ingestion of small stones served an antiparasite function and whether this behavior differed between the sexes. At a Lake Ontario site, females more often had small stones in their stomachs and were less parasitized by nematodes than were males, and males with small stones had fewer nematodes than males without small stones. We did not find similar patterns in small stone presence or parasitism at a Lake Erie site; however, Lake Erie birds had fewer parasites and lower proportions of birds with small stones. These results suggest that ingestion of small stones by Double-crested Cormorants might indeed serve an antiparasite function.

For hummingbirds, artificial feeders can serve as an alternative food source to nectar from flowering plants. The presence of feeders may lead to increases in local hummingbird populations and decreases in the use of native plants. We examined how the presence of feeders influenced the rate of hummingbird visits to a changing array of flowering plants in southeastern Arizona. Feeder visits represented approximately 59% of all visits during our yearlong study, but were less common in times of high floral abundance. The ratio of feeder visits to total visits was negatively related to overall floral abundance and to the abundance of the hummingbird-favored plant, Calliandra californica. The regular use of feeders by hummingbirds, which increases during periods of low floral availability, may have important implications for pollinator-plant relationships by reducing plant reproductive output. Additionally, this inverse relationship may affect estimates of hummingbird abundance and must be considered when analyzing data from studies that use feeders to attract hummingbirds.

A great deal of research has been devoted to the study of the Spotted Owl (Strix occidentalis), particularly over the past quarter century. The problems faced by scientists working to achieve conservation of this species have required the development of new approaches and methods in data analysis, scientific inference, and conservation planning. Moreover, the substantial depth of information gathered during Spotted Owl studies provides an extensive platform upon which new ideas and methods can be tested and developed. Some of these advances are discussed in this paper. These contributions show that the study of the Spotted Owl has resulted in information and methods that are not only specific to the owl and its conservation but also are broadly relevant to ornithologists, ecologists, and wildlife managers.

Once established with reliability, the rules of flight feather replacement become an important component of comparative life-history studies. Here I illustrate the form of tables that should be used to describe the pattern and intensity of flight feather molt. Using a subset of original data summarizing primary, secondary, and rectrix molt in Western Kingbirds (Tyrannus verticalis), I show how to assign scores indicating direction of replacement and points where waves of molt started or will stop. Combining these scores across birds yields a molt summary table, the starting point for determining the rules of feather replacement. This raw summary table is then iterated to show breaks between molt series and how summary scores around these breaks are reassigned to acknowledge series breaks. Molt summary tables also give sample sizes, because the rules of flight feather replacement cannot reliably be inferred unless birds in active molt are available for all the feathers being considered.