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Woodcreepers (Dendrocolaptinae) represent a remarkably uniform group of brownish birds that move by hitching up tree trunks as they forage for arthropod prey. Despite these superficial similarities, we were able to uniquely differentiate the niches of all 13 species north of Manaus by integrating morphological traits (e.g., mass and bill size) with behavioral traits (e.g., sociality, stratum use, and foraging maneuvers). The 5 ant-following (myrmecophilous) species, with their larger bodies and heavier bills, were morphologically distinct from the 7 species that join mixed-species flocks. A combination of vertical stratum, mass, and bill length further distinguished among mixed-flocking species. Two canopy species—the solitary Dendrexetastes rufigula and the mixed-flocking Lepidocolaptes albolineatus—consistently foraged at higher strata than other species. For the remaining mixed-flocking species, the largest 3 species differed significantly by mass, whereas the smallest 3 species, which overlapped broadly in mass, were uniquely distinguished by bill length. The 5 ant-following species differed in their degree of specialization on ant swarms, from facultative (Hylexetastes perrotii) to obligate (Dendrocincla merula). The ant-followers also showed nearly discrete mass distributions that essentially differed by Hutchinsonian 1:1.3 ratios, which likely allows them to maintain interspecific dominance hierarchies at the front of raiding army ant swarms. The behaviors we quantified (sociality, vertical strata, and myrmecophily), together with morphology (mass and bill size), separated all 13 species. We speculate that niche partitioning and competitive exclusion allow each woodcreeper to uniquely access invertebrate prey, permitting coexistence and contributing to high alpha diversity at our study site.

How are rainforest birds faring in the Anthropocene? We use bird captures spanning > 35 years from 55 sites within a vast area of intact Amazonian rainforest to reveal reduced abundance of terrestrial and near-ground insectivores in the absence of deforestation, edge effects or other direct anthropogenic landscape change. Because undisturbed forest includes far fewer terrestrial and near-ground insectivores than it did historically, today's fragments and second growth are more impoverished than shown by comparisons with modern 'control' sites. Any goals for bird community recovery in Amazonian second growth should recognise that a modern bird community will inevitably differ from a baseline from > 35 years ago. Abundance patterns driven by landscape change may be the most conspicuous manifestation of human activity, but biodiversity declines in undisturbed forest represent hidden losses, possibly driven by climate change, that may be pervasive in intact Amazonian forests and other systems considered to be undisturbed.

Hurricanes can have strong effects on wildlife populations and their habitats, with complex positive and negative outcomes. I demonstrate the utility of Audubon Christmas Bird Count (CBC) data by comparing results of the first Creole CBC after Hurricanes Laura (Category 4 on 27 August) and Delta (Category 2 on 9 October) in 2020 against 7 years of pre-hurricane Creole CBC baseline data in coastal Cameron Parish, LA. Bird community structure following the hurricanes was significantly different compared to the previous 7 years. Species richness significantly decreased in core (i.e., absent from 2 or fewer baseline CBCs) and irregularly (absent from 3 or more baseline CBCs) occurring bird species. Particularly hard hit were landbirds, whereas waterfowl, waterbirds, and shorebirds were more likely to show positive responses. Marshbird and raptor counts had the most neutral post-hurricane responses. Migratory species across all 6 guilds were also less likely than resident species to show negative responses and more likely to show positive responses to the hurricanes. These results demonstrate differing vulnerabilities of birds to hurricanes, an understanding of which is critical for developing conservation strategies to minimize negative population effects in the face of future increased hurricane intensity.

Description, Since 1980, 30 to 69% of species have shown reductions in mass, increases in wing length, and decreases in mass:wing ratio., Warming from climate change is expected to reduce body size of endotherms, but studies from temperate systems have produced equivocal results. Over four decades, we collected morphometric data on a nonmigratory understory bird community within Amazonian primary rainforest that is experiencing increasingly extreme climate. All 77 species showed lower mean mass since the early 1980s—nearly half with 95% confidence. A third of species concomitantly increased wing length, driving a decrease in mass:wing ratio for 69% of species. Seasonal precipitation patterns were generally better than temperature at explaining morphological variation. Short-term climatic conditions affected all metrics, but time trends in wing and mass:wing remained robust even after controlling for annual seasonal conditions. We attribute these results to pressures to increase resource economy under warming. Both seasonal and long-term morphological shifts suggest response to climate change and highlight its pervasive consequences, even in the heart of the world’s largest rainforest.

Host specificity is a key element to our understanding of symbiont diversification and is driven by multiple macro- and microevolutionary processes. Broad scale (e.g., species-level) studies can uncover relevant processes such as cospeciation and host-switching that shape host-symbiont evolutionary histories.

Determination of a bird’s age or cohort is critical for studies on avian demography, occurrence patterns, behavior, and conservation management. Age designations have largely been developed in north-temperate regions and utilize calendar-based or seasonally based codes; however, in tropical regions and in the southern hemisphere, these coding systems have limited utility at best. To address these issues, we had previously devised the “WRP system,” based on the nomenclature of Humphrey and Parkes (H–P) and Howell et al., which defines molts in an evolutionary context applicable to birds globally. Here we refine and build upon core concepts and definitions of the WRP coding system, resolving key limitations that were identified during its first decade of use. The WRP system employs a three-letter alpha code in which each letter describes a different aspect of H–P terminology: the molt cycle (which informs a bird’s age) and molt and plumage status within the cycle (each of which can also inform age). Here we recommend the continued use of most of the original (“core”) WRP coding while augmenting the system with an optional adjunct-code entry for comprehensiveness, clarity, and flexibility, and we clarify a few additional codes to cover less common molting and plumage strategies. For most users, from 7 to 13 core and 1 adjunct WRP code will be sufficient to describe all plumages and provide molt status and ages for demographic studies or other purposes. The revised WRP system is flexible enough to be adapted to the specific goals of programs while also providing core codes that can facilitate the comparison of avian age, molt, and plumage status on a global basis. We anticipate that our revised and standardized version of the WRP system will be easily adopted and could eventually replace calendar-based and seasonally based coding.

Bergmann’s rule is a well‐established, ecogeographical principle that states that body size varies positively with latitude, reflecting the thermoregulatory benefits of larger bodies as temperatures decline. However, this principle does not seem to easily apply to migratory species that are able to avoid the extreme temperatures during winter at higher latitudes. Further, little is known about the ontogeny of this relationship across life stages or how it is influenced by ongoing global climate change. To address these knowledge gaps, we assessed the contemporary relationship between latitude and body size in a long‐distance migratory species, the prothonotary warbler (Protonotaria citrea) across life stages (egg to adult) on their breeding grounds. We also measured historic eggs (1865‐1961) to assess if the relationship between latitude and size during this life stage has changed over time. In accordance with Bergmann’s rule, we found a positive relationship between latitude and body mass during all post‐embryonic life stages, from early nestling stage through adulthood. We observed this same predicted pattern with historic eggs, but contemporary eggs exhibited the reverse (negative) relationship. We suggest that these results indicate a genetic component to this pattern and speculate that selection for larger body size in altricial nestlings as latitude increases may possibly drive the pattern in migratory species as even rare extreme cold weather events may cause mortality during early life stages. Furthermore, the opposite relationships observed in eggs, dependent on time period, may be related to the rapidly warming environments of higher latitudes that is associated with climate change. Although it is unclear what mechanism(s) would allow for this recent reversal in eggs (but still allow for its maintenance in later life stages). This evidence of a reversal suggests that anthropogenic climate change may be in the process of altering one of the longest‐standing principles in ecology., Following Bergmann's rule, a positive relationship existed between latitude and body mass during all post‐embryonic developmental stages in a long‐distance migratory bird species, the prothonotary warbler (Protonotaria citrea). As this pattern appeared during the first days posthatching, these data suggest that the benefits of larger body size in colder environments may accumulate at an early age in altricial migratory species and may support the hypothesis of a genetic component underlying this pattern.

Estimates of migratory connectivity are needed for full annual cycle population models of migratory bird species experiencing rapid declines in abundance. One technique to determine migratory connectivity is through stable isotope analysis. This low-resolution method may be influenced by how data are calibrated between isotopes measured in precipitation and those measured in feathers, and can be informed by incorporating relative abundance into the assignment model. eBird abundance maps are a new tool combining citizen science data into a predictive species distribution model. In the Prothonotary Warbler (Protonotaria citrea), a wetland-associated songbird with a patchy breeding distribution, we sought to use stable-hydrogen isotope analysis informed by a species-specific calibration equation and eBird abundance data to determine the strength of migratory connectivity. We developed a species-specific calibration equation using known-origin samples from the breeding grounds and found that stable-hydrogen isotope values measured in precipitation explained 50% of the variation in stable-hydrogen isotope values among feathers. We found that the assignment model incorporating eBird abundance data correctly identified the true origins of 66% of individuals, and that the average assignment area (as a measure of precision) was 64% of the breeding distribution. These results represented a 7% increase in precision and a 3% decrease in accuracy when compared to a model that was not informed by abundance. Based on these models, wintering populations from 6 countries represented a mix of likely breeding origins, suggesting low migratory connectivity for Prothonotary Warblers. We found evidence that wintering latitude was related to likely breeding origin, with individuals at western wintering locations more likely to have southern breeding origins, but this relationship was weak. These results corroborate studies using archival light-level geolocators and high-resolution genetic markers, which also demonstrated weak migratory connectivity in this species. For patchily distributed species, eBird abundance data may not provide a useful increase in precision and accuracy for isotope assignments.

Although species lists from throughout Amazonia have become available, relatively complete inventories based on longterm work remain rare. Longitudinal comparisons at well-studied sites provide the best opportunities for describing communities and identifying changes in regional avifaunas. Within central Amazonia, no region has received as much consistent ornithological coverage as the terra firme forests north of Manaus, Brazil, at the Biological Dynamics of Forest Fragments Project (BDFFP). Here we provide an updated list of the area, including notes on all species added between 1997 and 2017. We recorded 21 species new for the site, most of which (>75%) are birds that prefer varzea or second-growth forest. This brings the cumulative BDFFP list up to 409 species, the majority (66%) of which inhabit primary terra firme forest. Together, this confirms that the regional terra firme community had been well-characterized by the 1990s, and that species additions to the list over the last 20 years are consistent with a changing landscape as urbanization, agriculture, and second-growth spread from Manaus. The final product continues to represent the most complete avian inventory for a single site in all of lowland Amazonia.

One of the greatest challenges to informed conservation of migratory animals is elucidating spatiotemporal variation in distributions. Without such information, it is impossible to understand full-annual-cycle ecology and effectively implement conservation actions that address where and when populations are most limited. We deployed and recovered light-level geolocators (n = 34) at 6 breeding sites in North America across the breeding range of a declining long-distance migratory bird, the Prothonotary Warbler (Protonotaria citrea). We sought to determine migratory routes, stopover location and duration, and the location of overwintering grounds. We found that the species exhibits a large-scale, east‒west split in migratory routes and weak migratory connectivity across its range. Specifically, almost all individuals, regardless of breeding origin, overlapped in their estimated wintering location in northern Colombia, in an area 20% the size of the breeding range. Additionally, most of the individuals across all breeding locations concentrated in well-defined stopover locations in Central America while en route to Colombia. Although error inherent in light-level geolocation cannot be fully ruled out, surprisingly much of the estimated wintering area included inland areas even though the Prothonotary Warbler is considered a specialist on coastal mangroves in winter. Based on these results, conservation efforts directed at very specific nonbreeding geographical areas will potentially have benefits across most of the breeding population. Our findings highlight the importance of using modern technologies to validate assumptions about little-studied portions of a species’ annual cycle, and the need to distribute sampling across its range.

Understanding how animals move in a complex habitat mosaic is critical to biodiversity conservation as deforested lands and secondary rainforests accumulate in landscapes previously dominated by primary forests. To visualize the spatiotemporal dynamics of secondary forest recovery after pasture abandonment, we formed a conceptual model predicting avian space use during a temporal sequence beginning with deforestation and continuing through regrowth of old secondary forest. We tested five predictions of the model at the Biological Dynamics of Forest Fragments Project near Manaus, Brazil, using 73 radio-tagged understory insectivores of three species: two woodcreepers (Glyphorynchus spirurus, Xiphorhynchus pardalotus) and a terrestrial antthrush (Formicarius colma). Both woodcreepers provided evidence to support all predictions except that of greater path tortuosity in primary forest. Woodcreepers using secondary forest had larger home ranges, larger core areas, and faster movement rates than in primary forest. Further, the proportion of all species' core areas in primary forest exceeded the proportion of home ranges in primary forest. Formicarius colma showed a fundamentally different pattern than the woodcreepers: it essentially avoided secondary forest until 27–31 years after pasture abandonment, at which point movements were indistinguishable from those in primary forest. Formicarius colma and other terrestrial insectivores show implastic spatiotemporal responses to recovering secondary growth, which we suspect contributes to the sensitivity of this guild to forest disturbance. Quantifying the value of marginal (and economically inconsequential) habitats such as secondary forest will be essential as land managers strive to maintain species persistence and connectivity in increasingly heterogeneous tropical landscapes.

Primary tropical rain forests are being rapidly perforated with new edges via roads, logging, and pastures, and vast areas of secondary forest accumulate following abandonment of agricultural lands. To determine how insectivorous Amazonian understory birds respond to edges between primary rain forest and three age classes of secondary forest, we radio-tracked two woodcreepers (Glyphorynchus spirurus, N = 17; Xiphorhynchus pardalotus, N = 18) and a terrestrial antthrush (Formicarius colma, N = 19). We modeled species-specific response to distance to forest edge (a continuous variable) based on observations at varying distances from the primary-secondary forest interface. All species avoided 8-14-yr-old secondary forest. Glyphorynchus spirurus and F. colma mostly remained within primary forest 100 m into secondary forest 27-31 yr old. Young Formicarius colma and most G. spirurus showed a unimodal response to 8-14-yr-old secondary forest, with relative activity concentrated just inside primary forest. After land abandonment, G. spirurus was the first to recover to the point where there was no detectable edge response (after 11-14 yr), whereas X. pardalotus was intermediate (15-20 yr), and F. colma last (28-30 yr +). Given the relatively quick recovery by our woodcreeper species, new legislation on protection of secondary forests > 20-yr old in Brazil's Pará state may represent a new opportunity for conservation and management; however, secondary forest must mature to at least 30 yr before the full compliment of rain forest-dependent species can use secondary forest without adverse edge effects. Florestas tropicais primárias têm sido rapidamente perfuradas com novas bordas devido estradas, extração de madeira e criação de gado, gerando vastas áreas de floresta secundária que surgem após o abandono de áreas desflorestadas. Para determinar como aves insetívoras de sub‐bosque da Amazônia Central respondem ao efeito de borda entre floresta primária e três classes etárias de florestas secundárias, nós monitoramos com a ajuda de rádio‐transmissores, dois dendrocolaptídeos (Glyphorynchus spirurus, N = 17; Xiphorhynchus pardalotus, N = 18), e um formicarídeo terrestre (Formicarius colma, N = 19). Nós modelamos respostas espécie‐específicas para a distância até a borda da floresta (variável contínua), baseadas em observações de distâncias variadas na interface entre a floresta primária e secundária. Glyphorynchus spirurus e F. colma permaneceram a maior parte do tempo dentro da floresta primária, < 100 m da borda jovem. Jovens de F. colma raramente adentraram > 100 m da floresta secundária mais velha (27–31 anos). Os jovens de F. colma e a maioria dos G. spirurus mostraram uma resposta unimodal em relação as florestas secundárias jovens, com atividade concentrada apenas dentro da floresta primária. Após o abandono da terra, G. spirurus foi o primeiro a demonstrar não haver mais um efeito detectável da borda (após 11–14 anos), enquanto que X. pardalotus apresentou uma resposta intermediária (15–20 anos), e F. colma a mais longa (28–30 anos +). Diante da recuperação relativamente rápida dos Dendrocolaptídeos, uma nova legislação que proteja florestas secundárias >20 anos no estado brasileiro do Pará pode representar uma nova oportunidade para a conservação e manejo. No entanto, a floresta secundária deve amadurecer por, pelo menos, 30 anos antes que toda a comunidade de espécies dependentes das floresta primária possa usar a floresta secundária sem os efeitos adversos das bordas. Fil: Powell, Luke L.. Instituto Nacional de Pesquisas da Amazônia; Brasil. National Zoological Park. Smithsonian Migratory Bird Center; Estados Unidos. State University of Louisiana; Estados Unidos Fil: Zurita, Gustavo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina Fil: Wolfe, Jared D.. Instituto Nacional de Pesquisas da Amazônia; Brasil. State University of Louisiana; Estados Unidos. United States Department of Agriculture. Forest Service. Redwood Sciences Laboratory; Estados Unidos Fil: Johnson, Erik I.. Instituto Nacional de Pesquisas da Amazônia; Brasil. State University of Louisiana; Estados Unidos. National Audubon Society; Estados Unidos Fil: Stouffer, Phillip C.. State University of Louisiana; Estados Unidos. Instituto Nacional de Pesquisas da Amazônia; Brasil

Prothonotary Warblers (Protonotariacitrea) are Nearctic-Neotropic migrants that have experienced declining populations over the past 50 yr. Determining their migration routes and wintering areas are critical steps in identifying habitats used by species and populations of conservation concern. We captured a male Prothonotary Warbler on its breeding territory in Louisiana in June 2013 and attached a geolocator. We recaptured this male in March 2014 and analysis of the geolocator data revealed that the male traveled an estimated 7950 km through seven countries. Fall migration was characterized by movements south into Central America on 13 August 2014, then east to the Greater Antilles for about 1 mo, followed by a second movement south to Panama or Colombia on 15 November 2014 where the male remained for the rest of the winter. Spring migration occurred rapidly, with the bird leaving its southern wintering area on 4 March 2014 and returning to its breeding territory on 23 March 2014. The movements of this male Prothonotary Warbler add to accumulating evidence that many migrant birds exhibit either prolonged stopover behavior or secondary migratory movements. Factors contributing to prolonged stopover behavior or additional migratory movements of the Prothonotary Warbler in our study warrant further investigation.

Given rates of deforestation, disturbance, and secondary forest accumulation in tropical rainforests, there is a great need to quantify habitat use and movement among different habitats. This need is particularly pronounced for animals most sensitive to disturbance, such as insectivorous understory birds. Here we use multistate capture–recapture models with radiotelemetry data to determine the successional stage at which within-day movement probabilities of Amazonian birds in secondary forest are similar to those in primary forest. We radio-tracked three common understory insectivore species in primary and secondary forest at the Biological Dynamics of Forest Fragments project near Manaus, Brazil: two woodcreepers, Glyphorynchus spirurus (n = 19) and Xiphorhynchus pardalotus (n = 18), and the terrestrial antthrush Formicarius colma (n = 19). Forest age was a strong predictor of fidelity to a given habitat. All three species showed greater fidelity to primary forest than to 8–14-year-old secondary forest, indicating the latter’s relatively poor quality. The two woodcreeper species used 12–18-year-old secondary forest in a manner comparable to continuous forest, but F. colma avoided moving even to 27–31-year-old secondary forest—the oldest at our site. Our results suggest that managers concerned with less sensitive species can assume that forest reserves connected by 12–18-year-old secondary forest corridors are effectively connected. On the other hand, >30 years are required after land abandonment before secondary forest serves as a primary forest-like conduit for movement by F. colma; more sensitive terrestrial insectivores may take longer still.