Studying the geographic variation of phenotypic traits can provide key information about the potential adaptive function of alternative phenotypes. Gloger's rule posits that animals should be dark- vs. light-colored in warm and humid vs. cold and dry habitats, respectively. The rule is based on the assumption that melanin pigments and/or dark coloration confer selective advantages in warm and humid regions. This rule may not apply, however, if genes for color are acting on other traits conferring fitness benefits in specific climes. Covariation between coloration and climate will therefore depend on the relative importance of coloration or melanin pigments and the genetically correlated physiological and behavioral processes that enable an animal to deal with climatic factors. The Barn Owl (Tyto alba) displays three melanin-based plumage traits, and we tested whether geographic variation in these traits at the scale of the North American continent supported Gloger's rule. An analysis of variation of pheomelanin-based reddish coloration and of the number and size of black feather spots in 1,369 museum skin specimens showed that geographic variation was correlated with ambient temperature and precipitation. Owls were darker red in color and displayed larger but fewer black feather spots in colder regions. Owls also exhibited more and larger black spots in regions where the climate was dry in winter. We propose that the associations between pigmentation and ambient temperature are of opposite sign for reddish coloration and spot size vs. the number of spots because selection exerted by climate (or a correlated variable) is plumage trait–specific or because plumage traits are genetically correlated with different adaptations.

Understanding the biogeographic origins and temporal sequencing of groups within a region or of lineages within an ecosystem can yield important insights into evolutionary dynamics and ecological processes. Fifty years ago, Ernst Mayr generated comprehensive—if limited—inferences about the origins of the New World avifaunas, including the importance of pre-Isthmian dispersal between North and South America. Since then, methodological advances have improved our ability to address many of the same questions, but the phylogenies upon which such analyses should be based have been incompletely sampled or fragmentary. Here, we report a near-species-level phylogeny of the diverse (~832 species) New World clade Emberizoidea—the group that includes the familiar sparrows, cardinals, blackbirds, wood-warblers, tanagers, and their close relatives—to our knowledge the largest essentially complete (≥95%) phylogenetic hypothesis for any group of organisms. Biogeographic analyses based on this tree suggest initial dispersal into the New World via Beringia, with rapid subsequent diversification, including early dispersal of 1 lineage (the tanagers, Thraupidae) into South America. We found substantial dispersal between North and South America prior to closure of the Isthmus of Panama, but with a notable increase afterward, with a directional bias from north to south. With much greater detail and historical rigor, these analyses largely confirm Mayr's speculations based on taxonomy, resolving outstanding ambiguity regarding the continental origins of some groups such as the Emberizidae and Icteridae. The phylogeny reported here will be a resource of broad utility for addressing additional evolutionary and ecological questions with this diverse group.

Although birds are generally known for their vocally produced songs and calls, some species have evolved alternate means of acoustic communication that do not require the syrinx. While many of these mechanical sounds are used in a courtship context, the importance of among- and within-individual variation in these sounds is almost entirely unknown. We investigated feather-produced sounds in male Greater Sage-Grouse (Centrocercus urophasianus), which congregate on leks during the spring breeding season and perform elaborate displays to attract females. Despite decades of research on the vocal components of the display, the frequency-modulated and mechanically generated “swish” sounds remain poorly studied. We used 2 years of acoustic data to evaluate the relationship between the time and frequency characteristics of the swish display and male mating success. Although characteristics of the swish sounds showed individual-specific patterns of variation, neither univariate nor multivariate analyses revealed direct effects of the acoustic qualities of these mechanical sounds on number of copulations. However, we did find that the frequency range of individual notes was correlated with note duration, and that males who successfully copulated showed a larger frequency range for a given duration than unsuccessful males. Furthermore, successful males increased this frequency change more strongly with the approach of a female than did unsuccessful males. These results parallel previous findings that successful and unsuccessful males show different patterns of adjustment with changing courtship conditions. Our results emphasize the importance of considering the interaction among multiple components of displays in analyses of mate choice, and help to broaden our understanding of the function of mechanical sounds in this and other species of birds.

Brood parasites typically impose costs on their hosts, which select for host defenses. However, where defenses are costly, hosts can benefit by facultative expression of defenses in relation to the risk of parasitism. The results of our model-presentation experiments show that Superb Fairy-wrens (Malurus cyaneus) mediate vigilance around their nest according to their perceived risk of brood parasitism; when the risk of parasitism is high, they increase the time they spend in the vicinity of their nests. In combination with previous studies, these data suggest that Superb Fairy-wrens have a plastic defense portfolio that can be acquired rapidly and deployed facultatively to prevent parasitism while minimizing wasteful investment in defenses in the absence of parasitism.

Ornithologists have largely embraced the molt terminology of Humphrey and Parkes (1959) as modified by Howell et al. (2003; the H-P-H system). In a recent commentary, Wolfe et al. (2014) summarized the derivation and benefits of H-P-H terminology, suggested slight modifications, and promoted analyses on the evolution of molts using H-P-H nomenclature. We appreciate the timeliness of Wolfe et al.'s review and agree with most of their conclusions and modifications. We disagree, however, with Wolfe et al.'s proposal for introducing a new and restricted use of the term “definitive” in H-P-H nomenclature. To avoid confusion, we recommend that definitive plumage and definitive molt cycle continue to be used as defined by Humphrey and Parkes (1959) and Howell et al. (2003), respectively, as terms indicating that plumage appearance and molt cycle have achieved stasis. We also recommend that the term “plumage” can be used more widely than the definition proposed by Humphrey and Parkes (1959), and that the term “juvenal” can henceforth be replaced by “juvenile” in molt and plumage literature.

The shortening of day lengths is known to advance the late-summer and autumn events of the annual cycle preceding migration in late-hatched individuals in order to synchronize the individual cycles of birds that hatched on different dates. However, little is known about how day length influences behavior during autumn migration. Here, we tested the locomotory activity of first-year migrant Long-tailed Tits (Aegithalos c. caudatus) from northwestern Russia under two different photoperiodic conditions during the autumn migration period. The birds were taken into the experiment after they started their migration in the wild, and assigned to either the control (natural photoperiod) or the experimental group (photoperiod shifted 1 mo ahead to simulate shorter days). In the beginning of the experiment, locomotory activity was the same in both groups. After 3 weeks, however, individuals exposed to the light regime simulating a delay on the migration route (i.e. shorter days) showed higher levels of locomotory activity. This reveals that Long-tailed Tits are photosensitive in October with respect to their migratory behavior, and suggests that migrants may use photoperiod to adjust the speed of migration to their position en route.

A recent study by Zink et al. (2013) raises questions about how to interpret negative results in studies when the distinctness of a species of conservation concern is in question. Zink et al. found no evidence for genetic or ecological distinctness of the coastal California Gnatcatcher (Polioptila californica californica). We discuss why the genetic markers they chose were not well suited to the question of distinctness and how they overinterpreted negative results in their genetic and ecological analyses. We reanalyze their genetic data and find evidence that several genetic loci show significant differentiation in the coastal California Gnatcatchers. We provide recommendations for best practices in determining distinctness in phenotype, genetics, and ecology for California Gnatcatchers and other populations of conservation concern.

Parrots are one of the most complex avian lineages worldwide, yet little is known about their patterns of movement and space use. Such information is vital for understanding the social development and structure of members of this long-lived order, as well as for the establishment of effective conservation and management actions for the many threatened or endangered species. While global positioning system (GPS) telemetry has been employed successfully on a broad range of birds, to date no studies have been published in which this technology has been used on any psittaciform species, most probably due to concerns held by researchers regarding the high cost of GPS units or the perceived ability of members of this order to remove or damage tracking gear. Here, we evaluate the feasibility and performance of animal-borne GPS telemetry as a means of tracking parrots. First, we encased inexpensive (<US$70) archival GPS dataloggers (~19 g) in bite-proof housing, and then we evaluated the effects of the devices on the study animals and their operational performance during field trials (n = 14) on wild-caught Kea (Nestor notabilis), a large (~1 kg) parrot endemic to the Southern Alps of New Zealand. We observed no apparent adverse effects of the loggers on the behavior and condition of the Kea and no damage to the devices that impaired their function, and found that the operational performance of the loggers was similar to that reported for devices deployed on other birds and animals. Our study demonstrates that GPS telemetry can be a highly effective method for characterizing the movement patterns of free-ranging parrots.

Researchers have long recognized that the process of observing nests may influence nest success by increasing depredation risk or causing females to abandon nests. The effects of observer-related nest abandonment may also reduce estimates of daily nest survival when time to nest fate is reduced and the average nest exposure period within the sample becomes shorter. We used an 8-yr record of observer visitations of nesting female Greater Sage-Grouse (Centrocercus urophasianus) in central Nevada, USA, to assess whether observers influenced either the probability of daily nest survival or the overall probability of nest success. Because nest success is influenced by factors other than visitation, we also accounted for the overall quality of a nest (i.e. probability of success in the absence of observer effects) based on potential confounding factors. Nest visitation (no flushing) had no effect on daily nest survival, regardless of nest quality or female age. Flushing a female from a nest substantially lowered the probability of the nest surviving the following day (maximum ~0.22). When considered in the context of the entire nest exposure period, however, flushing a female once produced only a marginal reduction in overall nest success (~0.015). Additionally, females that were younger, or that were associated with low-quality nests, were more likely to abandon the nest after flushing, compared with older females or those associated with higher-quality nests. Observer-related abandonment, however, introduced a negative bias (~0.07) into estimates of overall nest survival by reducing the average timing of nest fate and thereby lowering daily nest survival. Our results suggest that the act of flushing female Greater Sage-Grouse may bias estimates of nest survival low, but this is due to an effect on estimates of daily nest survival, rather than an actual influence on the probability of nest fate.

The use of stable isotopes in animal ecology depends on accurate descriptions of isotope dynamics within individuals. The prevailing assumption that laboratory-derived isotopic parameters apply to free-living animals is largely untested. We used stable carbon isotopes (δ¹³C) in whole blood from migratory Dunlin (Calidris alpina arcticola) to estimate an in situ turnover rate and individual diet-switch dates. Our in situ results indicated that turnover rates were higher in free-living birds, in comparison to the results of an experimental study on captive Dunlin and estimates derived from a theoretical allometric model. Diet-switch dates from all 3 methods were then used to estimate arrival dates to the Arctic; arrival dates calculated with the in situ turnover rate were later than those with the other turnover-rate estimates, substantially so in some cases. These later arrival dates matched dates when local snow conditions would have allowed Dunlin to settle, and agreed with anticipated arrival dates of Dunlin tracked with light-level geolocators. Our study presents a novel method for accurately estimating arrival dates for individuals of migratory species in which return dates are difficult to document. This may be particularly appropriate for species in which extrinsic tracking devices cannot easily be employed because of cost, body size, or behavioral constraints, and in habitats that do not allow individuals to be detected easily upon first arrival. Thus, this isotopic method offers an exciting alternative approach to better understand how species may be altering their arrival dates in response to changing climatic conditions.

Our recent work on Monk Parakeets (Myiopsitta monachus) reported dominance steepness values that were inaccurate because of a bug in the analysis program. Updated steepness values are more moderate than initially reported, which places captive Monk Parakeet groups midway between egalitarianism and despotism.

Clutch size commonly decreases with increasing elevation among temperate-zone and subtropical songbird species. Tropical songbirds typically lay small clutches, thus the ability to evolve even smaller clutch sizes at higher elevations is unclear and untested. We conducted a comparative phylogenetic analysis using data gathered from the literature to test whether clutch size varied with elevation among forest passerines from three tropical biogeographic regions—the Venezuelan Andes and adjacent lowlands, Malaysian Borneo, and New Guinea. We found a significant negative effect of elevation on variation in clutch size among species. We found the same pattern using field data sampled across elevational gradients in Venezuela and Malaysian Borneo. Field data were not available for New Guinea. Both sets of results demonstrate that tropical montane species across disparate biogeographic realms lay smaller clutches than closely related low-elevation species. The environmental sources of selection underlying this pattern remain uncertain and merit further investigation.

Full-annual-cycle (FAC) models integrate seasonal demographic and environmental processes to elucidate the factors that limit and regulate animal populations. Unlike traditional, breeding-season-focused models of migratory populations, FAC population models include the effects on population dynamics of events in both the breeding and the nonbreeding season (i.e. winter and migration). Given that migratory birds can spend most of the year away from the breeding grounds and face seasonally specific threats and limitation, FAC models can provide critical and unique insights about their population dynamics. We review existing FAC population model types, including demographic network models, seasonal matrix models, and individual-based models, with examples of each type. We also suggest some approaches new to FAC population modeling—integrated population models and integral projection models—and make recommendations for the development and implementation of these models. Incorporating model components such as density dependence, migratory connectivity (the demographic linkages between breeding and nonbreeding areas), and seasonal interactions can be critical for model realism but can also increase model complexity and development time. Much of the development of FAC population models has been more theoretical than applied. The main limitation to the application of the developed models is availability of empirical data for all annual stages, particularly knowledge of migratory connectivity and density-dependent seasonal survival. As these data become more available, the models outlined here should find additional uses.

We describe Scytalopus perijanus (Perijá Tapaculo), a new species in the family Rhinocryptidae (suborder Tyranni) found in humid montane and elfin forests (1,600–3,225 m elevation) in the Serranía de Perijá of Colombia and Venezuela. Although specimens of this taxon have been available in museums since 1941, they were not carefully studied and were ascribed to different taxa of the latebricola and atratus groups. We obtained a modern series of specimens that, coupled with analysis of vocal and genetic data, clarified this taxonomic puzzle. The new Scytalopus exhibits distinctive morphological and vocal traits with respect to all other known species and represents a differentiated evolutionary lineage within a clade of northern species, including S. meridanus, S. caracae, and S. latebricola. The new species has not been recorded in sympatry with any other Scytalopus, but it may overlap at lower elevations with S. atratus nigricans, although each uses different microhabitats. Ecological niche modeling indicates that the new species currently has a restricted geographic range within the Serranía de Perijá, where large extents of natural habitat have been cleared and fragmented, particularly on the Colombian slopes. Scytalopus perijanus, however, is uncommon to fairly common in forest fragments, tall secondary forest patches, elfin forest, and paramo vegetation at the treeline.

Birds are maniraptoran theropod dinosaurs. The evidence supporting the systematic position of Avialae as a derived clade within Dinosauria is voluminous and derived from multiple independent lines of evidence. In contrast, a paucity of selectively chosen data weakly support, at best, alternative proposals regarding the origin of birds and feathers. Opponents of the theory that birds are dinosaurs have frequently based their criticisms on unorthodox interpretations of paleontological data and misrepresentation of phylogenetic systematic methods. Moreover, arguments against the nested position of Avialae in Dinosauria have often conflated the logically distinct questions of avian origins, the evolution of flight, and the phylogenetic distribution of feathers. Motivated by a Perspectives article with numerous factual inaccuracies that recently appeared in The Auk, we provide a review of the full complement of facts pertaining to the avian origins debate and address the misplaced criticisms raised in that opinion paper.

Phylogenetic methods increasingly are brought to bear on questions of subspecies taxonomy, but several recent examples highlight the need for a clear and consistent philosophical approach to how genetic data are used to assess subspecies limits. Such standards are crucial conceptually, whether or not taxonomic decisions affect conservation decisions, as they might in a recent study focused on the California Gnatcatcher (Polioptila californica), a taxon currently protected under the U.S. Endangered Species Act. It is also crucial that any adopted framework allows each of a full range of alternatives to be either supported or rejected. In this spirit, in addition to recommending best practices, I propose an amendment to the phylogenetic species concept to include a subspecies category.

Paleornithology, the study of fossil or ancient bird remains, provides an important context for understanding the biology, evolutionary history, and ecology of living birds. Recent technological and methodological advances in the field of paleornithology have opened up the potential to extract new pools of information from fossil bird remains, and hence provide new insights into the histories of living birds. Here we review some of these advances, covering aspects of ancient DNA and protein analyses, sedimentary proxies for birds, stable isotope analyses, coprolite analyses, high-resolution computed tomography, paleoneurology, finite elements analysis, and paleohistology. These new advances offer exciting prospects for the future of paleornithology, but also reaffirm the importance of basic fieldwork, exploration and the discovery of new fossil specimens, museum archives in which to curate the specimens, and traditional morphological approaches to studying the fossil remains.

Melanin is a common pigment in the plumage of birds, but the extent to which its deposition in feathers is condition dependent and can be used as a reliable signal of quality and reproductive performance is still much debated. In addition, the existence and function of melanin ornaments in female birds or in birds of different age classes has rarely been addressed. We studied the size and color of 4 melanin ornaments in the Northern Flicker (Colaptes auratus), a woodpecker, and found that the plumage patches became larger or darker with age class in both sexes. Consistent with the partly reversed sex roles of Northern Flickers and sexual selection in both sexes, several melanin ornaments were the same size in males and females and were correlated with body size or body condition. There was assortative pairing according to melanin ornaments when controlling for age, and 1 or more ornaments predicted laying date or clutch size of the pair independent of age. The results suggest that melanin ornaments in Northern Flickers may contain multiple messages and be used as cues of quality.