Most birds that show geographic variation in their songs discriminate between local and foreign songs, which may help them avoid unnecessary conflicts with vagrant individuals or similar-sounding congeners. However, some species respond equally to foreign and local songs, which may be useful if foreign individuals present territorial threats or if there are no sympatric congeners to avoid. Species

Energy acquisition and storage are important for survival and fecundity of birds during resource-limited periods such as spring migration. Plasma-lipid metabolites (i.e. triglyceride [TRIG], β-hydroxybutyrate [BOHB]) have been used to index changes in lipid stores and, thus, have utility for assessing foraging habitat quality during migration. However, such an index may be affected by energetic maintenance

AbstractMixed-species flocks constitute community modules that can help test mechanisms driving changes to community composition across environmental gradients. Here, we examined elevational patterns of flock diversity (species richness, taxonomic diversity, species, and guild composition) and asked if these patterns were reflections of the full bird community at a given elevation (open-membership

Ornithology lost one of its most productive and influential scientists of the late 20th and early 21st centuries with the passing of Storrs L. Olson on January 20, 2021, following a courageous battle with esophageal cancer. Storrs lived and breathed birds, especially from the standpoints of museum-based systematics, morphology, evolution, paleontology, biogeography, and nomenclature. His prolific and

Prinias (Cisticolidae: Prinia) are resident warblers of open areas across Africa and Asia and include many polytypic species whose species limits have not been seriously reevaluated recently. Based on an integrative taxonomic analysis of morphology, song, and mitochondrial DNA (mtDNA), we suggest that 2 species should be recognized in the Graceful Prinia (Prinia gracilis) complex. In addition, our

The following figures and figure captions contained errors outlined here in this correction document: (1) the y axis for Figure 2 was incorrectly labelled as “Discrimination Ratios”, and (2) the y axes and figure captions for Figures 3, 4, and 5 were incorrectly labelled (axes) and written (figure captions) as “Percent response”. The corrected figures and figure captions appear below. None of these

AbstractIdentifying population genetic structure is useful for inferring evolutionary process and comparing the resulting structure with subspecies boundaries can aid in species management. The American Kestrel (Falco sparverius) is a widespread and highly diverse species with 17 total subspecies, only 2 of which are found north of U.S./Mexico border (F. s. paulus is restricted to southeastern United

AbstractExamining differences among recently diverged populations can provide insight into the traits and evolutionary mechanisms that drive or maintain divergence. The genus Sturnella includes 2 recently diverged species, Sturnella magna (Eastern Meadowlark) and S. neglecta (Western Meadowlark), the former of which has a complex of subspecies distributed across the Americas. Of the S. magna subspecies

Elevational migration can be defined as roundtrip seasonal movement that involves upward and downward shifts in elevation. These shifts incur physiological challenges that are proportional to the degree of elevational change. Larger shifts in elevation correspond to larger shifts in partial pressure of oxygen, air density, temperature, and ultraviolet (UV) exposure. Although most avian examples of

Major articles appearing in the 38th volume of The Auk in 1921 included accounts of life history and behavior (11); systematics and nomenclature (10); bird lists by region (8); migration, irruption, and range expansion (3); bird banding (2); oology (1); a memorial; and annual reports of the secretary. Alfred Otto Gross (1883–1970) authored the lead article, an account of the life history of the Dickcissel

AbstractAccurately determining avian species limits has been a challenge and a work in progress for most of a century. It is a fascinating but difficult problem. Under the biological species concept, only lineages that remain essentially independent when they are in sympatry are clearly species. Otherwise, there is no clear line yet found that marks when a pair of diverging lineages (e.g., in allopatry)

The ornithological world has 4 global checklists (as of early 2020). While 3 follow the results of peer-reviewed research at varying pace and conservatism, the HBW/BirdLife checklist, which is adopted by the global Red List authority, has implemented Tobias et al.’s (2010) 7-point scoring system to overhaul global ornithological treatment. Critically received in some academic quarters, this scoring

Studying macroevolutionary patterns of phenotypic variation and their driving forces in large radiations can shed light on how biodiversity is generated across broad spatiotemporal scales. In this study, we integrated song and morphological variation across more than 300 species representing the largest family of songbirds, the tanagers (Thraupidae), to uncover how morphological variables of the vocal

AbstractFour main challenges that can underpin ongoing, intransigent debates about species limits in birds are reviewed: allopatry (population subdivision vs. speciation), geographically widespread introgression of mitochondrial DNA (mtDNA), recent speciation, and selection. Examples from birds of the Australian region show how these challenges, their interplay, and the molecular-phenotypic discordance

AbstractSex allocation theory predicts that parents should adjust their brood sex ratio to maximize fitness returns in relation to parental investment. Adaptive adjustment of sex ratio may be driven by differential costs of rearing sons and daughters or differential benefits of investing limited resources into offspring of different sex. In both cases, possible sex ratio bias should depend on parental

AbstractSpecies delimitation requires a broad assessment of population-level variation using multiple lines of evidence, a process known as integrative taxonomy. More specifically, studies of species limits must address underlying questions of what limits the distribution of populations, how traits vary in association with different environments, and whether the observed trait differences may lead

Species are fundamental to biology, conservation, and environmental legislation; yet, there is often disagreement on how and where species limits should be drawn. Even sophisticated molecular methods have limitations, particularly in the context of geographically isolated lineages or inadequate sampling of loci. With extinction rates rising, methods are needed to assess species limits rapidly but robustly

Despite the acknowledged importance of defining avian species limits to scientific research, conservation, and management, in practice, they often remain contentious. This is true even among practitioners of a single species concept and is inevitable owing to the continuous nature of the speciation process, our incomplete and changing understanding of individual cases, and differing interpretations

The Sensory Ecology of Birds by MartinGraham R.. 2017. Oxford University Press, Oxford, England. 320 pp. $105.00 (hardcover). ISBN 978-0-199-694532. $53.00 (paperback). ISBN 978-0-199-694549.

AbstractAlthough primary cavity-nesting species are capable of excavating new cavities, they often reuse old ones. To determine potential factors driving such reuse, we studied nest-cavity reuse in the Acorn Woodpecker (Melanerpes formicivorus), a cooperatively breeding species that reuses old cavities for 57.2% of nests at Hastings Reservation in central coastal California, USA. We found no evidence

Africa’s montane ecosystems are noteworthy not only for their isolation but for their morphologically similar bird populations that inhabit geographically disparate localities. Many species possess range disjunctions in excess of 2,000 km and appear to represent populations that have been isolated since at least the last Ice Age, including the Northern Double-collared Sunbird (Cinnyris reichenowi)

Millicent Ficken releasing a Golden-crowned Kinglet at the University of Wisconsin-Milwaukee Field Station (2005) (photo by Gretchen Meyer).

Habitat selection decisions can impact individual fitness and ultimately scale up to mediate population dynamics. Understanding how birds select habitat is thus critical for discerning the biological processes structuring populations and for developing conservation strategies, particularly for species in decline. Marbled Murrelet (Brachyramphus marmoratus; hereafter murrelet) populations have declined

Rainfall regime, the amount and timing of annual precipitation, can influence the breeding phenology, individual fitness, and population dynamics of tropical birds. In Neotropical regions with rainfall seasonality (i.e. wet and dry seasons), the warm phase of the El Niño Southern Oscillation (ENSO) can exacerbate seasonal drought and negatively impact avian survival and reproduction. However, the mechanisms

Understanding the evolutionary and ecological mechanisms that shape the spatial divergence of signals involved in reproductive isolation is a central goal in studies of speciation. For birds with innate songs, such as the suboscine passerine birds, the integration and comparison of both genetic and ecological factors in explaining song variation at the microevolutionary scale are rare. Here, we evaluated

Migrating animals occur along a continuum from species that spend the nonbreeding season at a fixed location to species that are nomadic during the nonbreeding season, essentially continuously moving. Such variation is likely driven by the economics of territoriality or heterogeneity in the environment. The Snowy Owl (Bubo scandiacus) is known for its complex seasonal movements, and thus an excellent

AbstractGiven the availability of genomic data to identify separately evolving groups of organisms, many researchers establish species limits based on assessments of the extent of gene flow among populations and often use analytical approaches to identify species in which gene flow is explicitly disallowed. Strictly considering lack of—or limited—gene flow as the main or only criterion to delimit species

AbstractWe compared support for 3 hypotheses that might explain observed morphological variation among islands of 4 species of Caribbean land birds: ecological release from competition and predation pressure, predation pressure from 1 novel predator species (small Indian mongoose, Herpestes auropunctatus), and climate. We measured wing chord, tarsus length, bill length, and mass of Bananaquits (Coereba

Disjunct distributions within a species are of great interest in systematics and biogeography. This separation can function as a barrier to gene flow when the distance among populations exceeds the dispersal capacity of individuals, and depending on the duration of the barrier, it may eventually lead to speciation. Here, we describe patterns of geographic differentiation of 2 disjunct populations of

AbstractStudying processes acting on differentiated populations upon secondary contact, such as hybridization, is important to comprehensively understand how species are formed and maintained over time. However, avian speciation studies in the tropical Andes have largely focused on the role of topographic and ecological barriers promoting divergence in allopatry, seldom examining hybridization and

AbstractArmy-ants (particularly swarm-raiding species Eciton burchellii and Labidus praedator) are keystone predators in Neotropical forests. Hundreds of associated species from diverse taxa depend on them for survival, the most conspicuous of which are the ant-following birds. These birds forage on cryptic arthropods and vertebrates as they attempt to escape raiding army-ants. Despite capturing the

AbstractThe slow-paced life history of many Neotropical birds (e.g., high survival and low fecundity) is hypothesized to increase lifetime fitness through investments in self-maintenance over reproduction relative to their temperate counterparts. Molt is a key investment in self-maintenance and is readily shaped by environmental conditions. As such, variation in molt strategies may be a key mechanism

We explored adaptive factors affecting the preformative molt in the passerine family Cardinalidae, and concluded that the ancestor inhabited forest habitats and underwent a partial preformative molt that included wing coverts but not primaries. Later radiations within the family appeared to be characterized by transitions from forests toward more open habitats, and such transitions also correlated

AbstractRapid high-intensity molt of flight feathers occurs in many bird species and can have several detrimental consequences, including reductions in flight capabilities, foraging performance, parental care, and plumage quality. Many migratory New World warblers (family Parulidae) are known to have intense remigial molt, and recent work has suggested that simultaneous replacement of the rectrices

AbstractAnimal culture changes over time through processes that include drift, immigration, selection, and innovation. Cultural change has been particularly well-studied for animal vocalizations, especially for the vocalizations of male animals in the temperate zone. Here we examine the cultural change in the vocalizations of tropical Rufous-and-white Wrens (Thryophilus rufalbus), quantifying temporal

AbstractCo-infection with microparasites (e.g., bacteria) and macroparasites (e.g., helminths) is often the natural state for wild animals. Despite evidence that gut helminths can bias immune responses away from inflammatory processes, few field studies have examined the role that helminths, or their potential interactions with internal microbial communities, play in modulating immunity in free-living

AbstractEastern (Vireo gilvus gilvus) and western (V. g. swainsoni) forms of the Warbling Vireo have essentially allopatric breeding ranges across north-central North America, but come into contact in central Alberta, Canada. In 1986, Jon Barlow presented preliminary morphological and song evidence suggesting that the Warbling Vireo complex might comprise more than one valid species. However, to date

Welcome to the first issue of Ornithology. While the title is new, this issue opens the 138th volume of an unbroken record of peer-reviewed, ornithological research that extends from The Auk’s first volume in 1884 (Figure 1) and, ultimately, from the 8 volumes of the Bulletin of the Nuttall Ornithological Club, started in 1876 (Allen et al. 1883). The new title is part of a long-term effort to increase

The annual meeting of the American Ornithologists’ Union (AOU) convened in Philadelphia at the Academy of Natural Sciences on November 7, 1921. Attendance was near 125. Among those present were 24 Members and 25 Fellows, of which 2 were founders, C. F. Batchelder (1856–1954) and A. K. Fisher (1856–1948). Also present were Retired Fellows W. K. Fisher (1878–1953) and N. T. Lawrence (1855–1928), as well

Milton W. Weller doing fieldwork in northern Minnesota.

The capacity for flight varies widely among bird species and influences their ecology, evolution, and conservation. Variation in vagility is influenced by behavioral responses to the nature of gaps between habitat elements as well as intrinsic characteristics of the species, particularly physiological traits influencing the physical capacity for sustained flight. Here, we briefly summarize the current

George Peck liked to call himself a nidiologist, a person who studies the nests and eggs of birds. While his chosen profession was to be a small-animal veterinarian, he pursued his passion for ornithology at every opportunity until his long life ended on June 20, 2020. As a child, George spent many weekends and holidays at the family cottage on the shore of the St. Lawrence River near Gananoque, Ontario

It is unusual in this age of bureaucratic conservation for one person’s name to be as closely linked to an endangered species recovery effort as Tom J. Cade’s was with the captive breeding, reintroduction, and eventual delisting of the Peregrine Falcon (Falco peregrinus) in North America. And although that may be his most memorable accomplishment, his career in ornithology and bird conservation was

AbstractSexual habitat segregation during the wintering period is a widespread phenomenon and has important implications for the ecology and conservation of migratory birds. We studied Black-and-white Warblers (Mniotilta varia) wintering in second-growth scrub and old-growth mangrove forest in Jamaica to quantify sexual habitat segregation and explore whether patterns of habitat occupation have consequences

This notice adds one new entry (#1 below) to the 61st Supplement to the Check-list of North American Birds (The Auk: Ornithological Advances 137:1–24; https://doi.org/10.1093/auk/ukaa030) and corrects errors in two entries (#2–3 below):

AbstractIn the Northern Hemisphere, several avian cavity excavators (e.g., woodpeckers) orient their cavities increasingly toward the equator as latitude increases (i.e. farther north), and it is proposed that they do so to take advantage of incident solar radiation at their nests. If latitude is a key driver of cavity orientations globally, this pattern should extend to the Southern Hemisphere. Here

Michael D. “Mike” Kern, an avian physiologist known particularly for his wide-ranging work on the physiology of songbirds, died on February 22, 2019 in Wooster, Ohio. He was a long-time faculty member in the Biology Department at The College of Wooster, and an Elective Member (1986) of the American Ornithologists’ Union (AOU).

Regina Macedo

AbstractStudying processes acting on differentiated populations upon secondary contact, such as hybridization, is important to comprehensively understand how species are formed and maintained over time. However, avian speciation studies in the tropical Andes have largely focused on the role of topographic and ecological barriers promoting divergence in allopatry, seldom examining hybridization and

André Dhondt

John Rotenberry

Jaime Collazo

Thomas Smith

William R. Dawson, pioneering avian ecophysiologist and long-time faculty member and administrator at the University of Michigan, died March 8, 2020, in Ann Arbor, Michigan. He was born August 24, 1927, in Los Angeles, California, the only child of William E. Dawson, an automotive electrician, and Mary H. Ryan, a bookkeeper. His father died when Bill was aged 5. Bill married Virginia (“Ginny”) Louise

AbstractThe Grallaria rufula complex is currently considered to consist of 2 species, G. rufula (Rufous Antpitta) and G. blakei (Chestnut Antpitta). However, it has been suggested that the complex, populations of which occur in humid montane forests from Venezuela to Bolivia, comprises a suite of vocally distinct yet morphologically cryptic species. We sequenced nuclear and mitochondrial DNA for 80

As in the past, most of the 90 Recent Literature reviews were done by Editor Witmer Stone while W. L. McAtee completed 7 and T. S. “Tombstone” Palmer completed 2. The number of papers reviewed nearly equaled the number of books. Reviews included reports, checklists, and pamphlets. Stone was also responsible for completing the lists, short reviews, and synopses that made up the quarterly sections titled

AbstractBirds exhibit remarkable variation in plumage patterns, both within individual feathers and among plumage patches. Differences in the size, shape, and location of pigments and structural colors comprise important visual signals involved in mate choice, social signaling, camouflage, and many other functions. While ornithologists have studied plumage patterns for centuries, recent technological

AbstractHaemosporidian parasites of the genera Plasmodium, Haemoproteus, and Leucocytozoon are among the best studied parasites of Neotropical birds. Here, we describe variation in haemosporidian prevalence (i.e. the proportion of infected individuals in a sampled population) in Neotropical birds. We review correlates of haemosporidian prevalence (including several avian life-history traits, climate

Bird Bonds: Sex, Mate-Choice and Cognition in Australian Native Birds by KaplanGisela. 2019. Pan McMillan Australia, Sydney, Australia. 354 pp., 50 color photographs and numerous black-and-white photographs, figures, and tables. $34.99 (trade paperback). ISBN 978-1-76055-420-0.