Wild bird feeding is a popular and growing activity, with approximately half of households participating in nations including the United States, Canada, the United Kingdom, New Zealand, and Australia. Supplemental feeding can increase survival and reproductive success of birds (which is often a goal of supplemental feeding efforts), but it raises concerns about phenological mismatch and possible increased risk of nest predation. Our objectives were to test whether access to supplemental food during the breeding season was correlated with (1) advanced egg-laying phenology, (2) increased clutch size, or (3) improved nest survival of 3 cavity-nesting species (Carolina Chickadee [Poecile carolinensis], Black-capped Chickadee [P. atricapillus], and Eastern Bluebird [Sialia sialis]) at a large spatial scale (the United States and Canada; spanning 22° latitude and 55° longitude). We examined data from 24,528 nest attempts submitted to NestWatch from 2014 to 2019. For Eastern Bluebirds, birds with access to supplemental insects initiated clutches 5.83 ± 0.89 (mean ± SE) days earlier than birds without access to food subsidies, whereas predicted nest survival was 5% greater for birds with access to supplemental insects (probability of nest success = 0.79, 95% CI: 0.77–0.81) than for birds without (0.74, 95% CI: 0.72–0.75). Clutch size of Eastern Bluebirds did not differ between birds with and without access to supplemental insects. For chickadees, supplemental feeding (of seeds, suet, insects, or fruit) was not correlated with phenology, clutch size, or nest survival. Our results suggest that supplemental feeding of insects can be an effective tool for increasing nest survival in Eastern Bluebirds and potentially other food-limited insectivores. However, the efficacy of supplemental feeding for improving reproductive success varies across taxa, likely related to diet. Despite widespread feeding of Black-capped and Carolina Chickadees, supplemental food had no discernable effect on timing of egg-laying, clutch size, or nest survival.

An understanding of the migratory connectivity between breeding and nonbreeding areas is fundamental to the management of long-distance migrants under pressure from habitat change along their flyways. Here we describe evidence for genetic structure within the nonbreeding range of the endangered Arctic-Canadian rufa subspecies of Red Knots (Calidriscanutus). Using blood and tissue samples from the major nonbreeding regions in Argentina (Tierra del Fuego and Río Negro), northern Brazil (Maranhão), and southeastern USA (Florida), we estimated genetic structure in 514 amplified fragment length polymorphism (AFLP) loci, applying cluster assignment analyses in DAPC, assignPOP, and STRUCTURE. Using a priori location information, individuals could be correctly re-assigned to their nonbreeding regions, which validated that the assignment accuracy of the data was sufficient. Without using a priori location information, we detected 3–5 genotype clusters, and posterior assignment probabilities of samples to these genotype clusters varied among the three regions. Lastly a chi-square test confirmed that allele frequencies varied significantly among nonbreeding regions, rejecting the hypothesis that samples were drawn from a single gene pool. Our findings hint at undescribed structure within the Red Knot rufa breeding range in the Canadian Arctic and indicate that each rufa nonbreeding area in this study hosts a different subsample of these breeding populations. The observation that nonbreeding sites of rufa Red Knots contain different genetic pools argues for separate conservation management of these sites.

Extreme weather events are becoming more frequent and severe, leading to an increase in direct, adverse thermoregulatory impacts on wildlife. Here, we document an unprecedented, single-day, heat-related mortality event of Magellanic Penguins (Spheniscus magellanicus) at Punta Tombo, Chubut Province, Argentina, one of the largest breeding colonies for this species. We found 264 dead adults and 90 dead chicks in the breeding colony and along the beaches after recording the highest temperature in the shade (44°C on January 19, 2019) since the study started in December 1982. We found dead adults and chicks in postures used to release heat (i.e. lying prone with flippers and feet extended away from the body and/or bills open). We found no evidence for other causes of mortality other than heat (e.g., disease, toxic algae, starvation). Adults potentially died of dehydration, because dead adults were in significantly worse body condition than adults that survived. Dead adults had either empty stomachs or <50 g of food, and 27% of the dead adults died traveling between the nesting area and the water. More males died than females (83% male and 17% female; n = 94). In one section of the colony, ∼5% of 1,153 adults died in the heat. Mortality rates of adults were unevenly distributed across the colony, suggesting that the presence of microclimates or easier beach access was an important factor to penguin survival. The body condition indices of dead and live chicks were similar and chicks that died from heat had food in their stomachs (mean = 405 ± 128 g; n = 14), suggesting that food likely inhibited their ability to thermoregulate. Documenting the effects of extreme weather events on populations is crucial to predicting how they will respond to climate change because these events, although rare, are expected to become more frequent and could have severe impacts on populations.

DNA metabarcoding is a popular tool for animal diet studies to address a variety of research topics across disciplines and taxa. Despite its widespread use, there has been relatively little focus on how digestion influences prey DNA detection and the description of a predator's diet. Fecal samples are a compelling source of dietary DNA because they are collected non-invasively. However, these samples may provide incomplete or inaccurate descriptions of diet because of differential digestion and DNA degradation across prey taxa during gut passage. This is especially pertinent for avian diet studies, which have widely adopted the use of fecal samples as a proxy for overall diet. To explore how digestion affects the recovery and detection of prey DNA in passerines, we used DNA metabarcoding to compare the recovery of prey DNA from paired stomach contents and fecal samples in Seaside Sparrows (Ammospiza maritima). Stomach contents produced ∼2.5 times greater DNA concentrations than fecal samples and—while this difference in DNA concentration was not statistically significant—stomach contents produced significantly more read identifications than fecal samples. However, these differences did not influence the description of diet, as similar measures of richness and diversity were found in both sample types. The relative read abundance of common prey families remained consistent between sample types, suggesting that while less DNA may survive digestion, the proportions of prey remain largely unaffected. We found no difference in the description of diet based on sample type at the population level, but our results show that comparing stomach and fecal samples from the same individual can reveal distinct foraging bouts. With no clear benefit to using stomach contents, we conclude that fecal samples are the preferred sample type for avian metabarcoding diet studies, unless research goals necessitate otherwise.

Imperfect detection in field studies on animal abundance, including birds, is common and can be corrected for in various ways. The binomial N-mixture (hereafter binmix) model developed for this task is widely used in ecological studies owing to its simplicity: it requires replicated count results as the input. However, it may overestimate abundance and be sensitive to even small violations of its assumptions. We used a 33-year dataset on the Marsh Tit (Poecile palustris), a sedentary forest passerine, from Białowieża Forest, Poland, to validate inference from binmix models by comparing model-estimated abundances to the true number of breeding pairs within the plots, determined by exhaustive population study. The abundance estimates, derived from 6 springtime (April and May) counts of males on each plot in each year, were highly reliable: 116 out of 132 year-plot estimates (88%) included the true number of pairs within the 95% confidence intervals. Over- and under-estimations were thus rare and similarly frequent (9 and 12 cases, respectively), with a tendency to overestimate at low densities and underestimate at high densities. Marsh Tits sing rarely but the frequency of countersinging increases with abundance, leading to nonindependence in detections. When accounted for in a submodel for detection, the per-survey number of countersinging events positively affected detection probability but only weakly affected abundance estimates. Simulations further demonstrate that this property, overestimation at low densities and underestimation at high densities, may be a systematic bias of binmix model even if density-dependent detection is absent. While the behavior of binmix models in specific situations requires more study, we conclude that these models are a valid tool to estimate abundance reliably when intensive population monitoring is not feasible.

Forecasting changes in size and distributions of populations is an essential component of conservation assessments. Such forecasts are only useful for species conservation and management when they are based on robust estimators of fecundity, survival, and density dependence. While apparent survival estimation is the main focus of mark–recapture modeling, fecundity and density dependence are rarely the subject of these models. Here, we present a Bayesian hierarchical framework that can estimate fecundity and density dependence along with age-based survival using only robust-design capture–recapture data. We refer to this framework as RD-pop. We used simulated capture histories to demonstrate that RD-pop can estimate vital rates and their density dependence with little bias. We applied RD-pop to capture history data from Brown Creeper (Certhia americana) and showed that estimates of fecundity are consistent with the breeding biology of this species. Finally, we illustrate that density dependence, even when estimated with uncertainty in the RD-pop framework, regularizes population dynamics and reduces the frequent population extinctions and explosions observed under density-independent models. RD-pop is a useful addition to the current mark–recapture modeling toolbox especially when the goal is to build population models that can make medium- and long-term projections. It can be applied to any population for which long-term robust-design mark–recapture data are available, and with slight modifications (incorporation of weather and climate effects on vital rates) has the potential to facilitate demographic projections under climate change.

Effective species conservation requires understanding environmental effects on stage-specific demographics driving population change. Northern Bobwhite (Colinus virginianus) is an early-successional shrub-obligate species that has experienced long-term, range-wide declines due to fire suppression, agricultural intensification, and sprawling development. Local habitat features and landscape context may interactively influence vital rates. Management affects food, cover, and other resources available locally, while surrounding landscapes often determine degree of isolation and predator communities. We evaluated relationships between juvenile bobwhite survival and local (50 m) and landscape (1 km) scale cover type composition and grassland management (i.e. conservation grazing, prescribed burns, mowing/haying) on 3 native grasslands and 2 traditionally managed conservation areas in southwest Missouri, USA, 2016–2018. We radio-tracked brood-attending adults and young from hatch to a maximum of 114 days and estimated juvenile survival with a Bayesian known-fate logistic exposure model. Juvenile survival was greatest on native grasslands that were burned and grazed at least once in the previous 2 years. Percent shrub cover was positively related to survival. Survival was relatively high in local agriculture, but these relationships were sensitive to surrounding landscape composition. For example, small patches of cropland surrounded by nonagriculture such as strip crops surrounded by grassland units on traditionally managed sites had low survival. Relationships between survival and agricultural landscape cover were dependent on local cover types; survival was high within crop fields but low in non-native grasslands surrounded by crop fields such as agricultural field borders. Patch-burn grazing practices on native grasslands provided the best habitat for bobwhite juvenile survival. Agricultural landscapes can support the recruitment of bobwhite if appropriately managed native grasslands are also available.

Over the last two centuries, the Red-and-Green Macaw (Ara chloropterus) has become locally extinct in Argentina. In an attempt to restore its key ecosystem functions as both disperser and regulator of large-seeded plants, a reintroduction project was initiated at the Iberá National Park in northeastern Argentina. The ability of released individuals to find food is crucial, especially when working with captive-bred animals, as long-term establishment of a self-sustaining population depends on their short-term ability to exploit wild food sources. Monitoring of feeding habits is usually conducted through behavioral observation, but in recent years DNA metabarcoding has emerged as an alternative for obtaining highly resolved data on diet composition. In this study, we use a combination of both techniques to characterize the breadth and composition of the reintroduced macaws' diet. In addition, we compare the efficiency of both observational and molecular techniques to assess diet composition in a frugivorous bird. Individuals fed on a variety of plant species (n = 49) belonging to a broad phylogenetic spectrum (28 families). Dietary richness estimated by direct observation and DNA metabarcoding was similar, though smaller than the combination of the two datasets as both techniques detected at least 15 species not recorded by the other method. While the total number of detected species was higher for observational data, the rate of species-detection per sampling day was higher for DNA metabarcoding. These results suggest that a combination of both methods is required in order to obtain the most accurate account of the total diversity of the diet of a bird species. The ability of reintroduced macaws to successfully exploit local food resources throughout the year indicates a good level of adjustment to the release site, an important step towards the creation of a stable, self-sustaining population of Red-and-Green Macaws in Northern Argentina.

Shorebirds have experienced a precipitous reduction in abundance over the past four decades. While some threats to shorebirds are widespread (e.g., habitat alteration), others are regional and may affect specific populations. Lesser Yellowlegs (Tringa flavipes) are long-distance migrants that breed across the North American boreal biome and have declined in abundance by 60–80% since the 1970s. The documented harvest of Lesser Yellowlegs in the Caribbean and northeastern South America during southward migration is a possible limiting factor for the species, but it is unknown to what extent birds from different breeding origins may be affected. To address the question of differential occurrence in harvest zones during southward migration, we used PinPoint GPS Argos transmitters to track the southward migrations of 85 adult Lesser Yellowlegs from across the species' breeding range and 80° of longitude from Anchorage, Alaska, USA, to the Mingan Archipelago, Quebec, Canada. We classified migratory locations as inside or outside three zones with high levels of harvest (Caribbean, coastal Guianas, and coastal Brazil) and then fit generalized additive mixed models to estimate the probability of occurrence of Lesser Yellowlegs in harvest zones according to their breeding origin. Individuals from the Eastern Canada population had a higher probability of occurrence within one or more harvest zones and remained in those zones longer than individuals breeding in Alaska and western Canada. Linear regressions also suggested that longitude of the breeding origin is an important predictor of occurrence in harvest zones during southward migration. Lastly, our findings, combined with other sources of evidence, suggest that current estimated harvest rates may exceed sustainable limits for Lesser Yellowlegs, which warrants further investigation.

The lack of high-quality information on data-poor species can hinder efforts to inform conservation actions via spatial distribution modeling. This is particularly true for tropical birds of conservation concern, for which ecological studies and assessments of their conservation status have received limited funding. Here we use a cost- and time-efficient protocol for assessing the distribution of range-restricted taxa and to identify priority areas for their conservation based on a sequential application of environmental niche models (ENMs) and occupancy-detection models. This approach first uses available geographical information and niche-theory to prioritize potential study sites, which can later be surveyed to obtain high-quality presence–absence data to accurately model distributional ranges with limited resources. We apply this protocol to identify priority areas for two Neotropical birds of conservation concern endemic to the Colombian Andes: Yellow-headed Brush-finch (Atlapetes flaviceps) and Tolima Dove (Leptotila conoveri). We first fitted ENMs using spatially filtered datasets containing all available records up to 2018. We then conducted field surveys across climatically suitable areas identified for both species, carrying out a total of 1,750 counts to generate input data for the occupancy models. Overall, our results suggested more extended and more continuous distribution ranges for both species than previously reported, but also identified population strongholds that are not currently represented within the national protected areas system. Both species occupied a narrow elevational belt (∼1,300–2,600 m above sea level) of the Central Andes of Colombia primarily on the slopes of the Magdalena River valley, with isolated populations in the Western and Eastern Andes; these areas have undergone some of the most marked landscape transformations in Colombia. This straightforward protocol maximizes available information and minimizes costs, while allowing for estimation of occurrence probabilities for range-restricted, data-poor taxa.

The Migratory Bird Treaty Act (MBTA) is critical to avian conservation in the United States, both through its protection of migratory birds and as a catalyst for a century of coordinated avian conservation. While more than 1,000 species are protected by MBTA, of extant bird species native to the continental U.S., only 20 species belonging to the order Galliformes are explicitly excluded. Management of galliforms has occurred largely without direct federal oversight, placing this group on a fundamentally different conservation path during the century following MBTA passage. In this paper, we review the historical context and biological justification for exclusion of galliforms from MBTA and synthesize how their present-day conservation differs from that of migratory birds. We find the most prominent difference between the two groups involves the scope of coordination among stakeholders. The U.S. government, primarily via the Department of Interior, acts as de facto coordinating body for migratory bird conservation and plays the central role in oversight, funding, and administration of management in the United States. In contrast, galliform management falls primarily to individual state wildlife agencies, and coordinated conservation efforts have been more ad hoc and unevenly spread across species. Migratory birds benefit from an almost universally greater scope of research and monitoring, scale of habitat conservation, and sophistication of harvest management compared with galliforms. Galliform harvest management plans, in particular, are less likely to use measurable objectives, reporting of uncertainty in population parameters, and explanation of harvest management techniques. Based on a review of species status lists (e.g., the U.S. Endangered Species Act), we found no evidence that galliforms were more frequently listed than migratory species. Regional trend estimates from the North American Breeding Bird Survey (BBS) were more likely to be negative for galliforms over the period 1966–2015, but this was primarily driven by Northern Bobwhite (Colinus virginianus). Data to assess galliform population status are generally poor, which complicates assessment for roughly half of galliform species. Increased support for coordination among state agencies and other stakeholders, similar to that applied to migratory birds, could help to ensure that galliform conservation is poised to tackle forthcoming challenges associated with global change.