Understanding how diet and life history strategies interact is important for exploring constraints of available nutrition on energetically expensive life history events in wild animals (i.e., reproduction, annual migration, molt). Previous research on migratory birds breeding in the Northern Hemisphere has demonstrated trophic niche shifts from invertebrates to fruit in order to fuel spring migration. We examined whether a trophic niche shift occurred in a Neotropical austral migrant, the Fork-tailed Flycatcher (Tyrannus savana savana), prior to spring migration by measuring stable nitrogen isotopes in feathers. We found that the austral migrant subspecies T. s. savana did appear to shift in diet from a higher to a lower trophic level (consistent in pattern with a shift from a higher to a lower ratio of invertebrates to fruit) but the shift occurred earlier than expected if it was preparation for migration. A sympatric sedentary subspecies occupying the same habitat (T. s. monachus) appeared to forage only at the lower trophic level during its annual molt and showed no evidence of a trophic niche shift; however, the molt of the 2 subspecies occurs at slightly different times of year. The timing of the trophic niche shift leads us to conclude that a higher trophic level diet early in molt is not related to preparation for spring migration but that it may be related to seasonal changes in food availability as the wet season concludes. A remaining challenge for understanding the ecological consequences of trophic niche shifts is to find ways to empirically measure trade-offs between different diets across energetically expensive life history events and compare these between taxa with differing life history strategies.

Great Salt Lake (GSL) is a critical staging area for 2 species of phalaropes: Wilson's (Phalaropus tricolor) and Red-necked (P. lobatus). Both rely on the abundant invertebrate prey at GSL to fuel their fall migrations to Central and South America, but little is known about where phalaropes forage on GSL, what foraging methods are used, or what variables influence their foraging decisions. During 2014 and 2015, the frequency of specific foraging behaviors by phalaropes differed by GSL bays; surface picking was the most common foraging behavior (≥50%) on Carrington and Gilbert bays while spinning was the most common on Farmington Bay. Most (60%) Red-necked Phalaropes used surface picking for foraging compared to 32% of Wilson's Phalaropes. Spinning behavior to upwell prey was more common in Wilson's Phalaropes (used by 19% of foraging birds) than Red-necked Phalaropes (3%). The proportion of phalaropes in a flock that were foraging was positively associated with biomass of invertebrate prey at the flock's location. Most (64%) of the phalarope flocks were on Farmington Bay, and 75% of phalaropes in this bay were foraging, compared to 41% of birds on Gilbert Bay. Thus, Farmington Bay is particularly important for hundreds of thousands of Red-necked and Wilson's phalaropes that stage on GSL for 4 months during each summer. Farmington Bay is brackish, shallow, and depends on the Jordan River for its freshwater. The future of this water source, and therefore Farmington Bay itself, is uncertain because of future diversions by humans and longer droughts predicted from climate change.

Cannibalism, the killing and eating of conspecifics of any life stage, leads to a variety of behavioral and ecological consequences and is influenced by a range of environmental circumstances among numerous taxa. In birds, cannibalism is particularly well known among gulls. Although multiple studies have linked cannibalism to egg and chick failure in gull populations, gull cannibal behavior is poorly understood. During the 2014 and 2015 breeding seasons, we observed the behavior of Glaucous-winged Gulls (Larus glaucescens) that used conspecific egg predation, a form of cannibalism, as a feeding tactic on Protection Island, Washington, USA. Most egg stealing by egg cannibals occurred during colony disturbances, especially by Bald Eagles (Haliaeetus leucocephalus), but egg stealing often occurred without concurrent disturbances. Among other findings, our data showed that egg cannibals were always males, the number of eggs stolen each day correlated with the daily number of eggs laid, egg cannibals ate fewer fish than non-cannibals, and the reproductive success of egg cannibals was lower than that of non-cannibals. This study provides the most comprehensive evaluation to date of how larid cannibals find, capture, and eat conspecific eggs, and it includes the first assessment of reproductive success of egg cannibals in comparison with non-cannibals.

Multi-year monitoring of species distribution is important for conservation planners to understand population trajectories. In New York, USA, the Eastern Whip-poor-will (Antrostomus vociferus) is among several bird species that have been documented to be declining and has been monitored for several years through large-scale surveys such as the Breeding Bird Atlas and Breeding Bird Survey. We implemented a study to assess trends in site occupancy at 19 survey routes during 2014–2018 breeding seasons. We surveyed for Eastern Whip-poor-wills following the Center of Conservation Biology Nightjar Survey Network methodology and used these data to estimate yearly relative abundance, factors that may influence the probability of detection, probability of a site being occupied and potentially important landscape features, and dynamic processes of site colonization and extinction. The mean relative abundance ranged from 0.54 in 2016 to 0.89 in 2014, with all yearly estimates having 95% confidence intervals that overlapped. The probability of detection was negatively affected by the greatest wind speeds recorded (12.87–28.97 kph, [8–18 mph]). Site occupancy was relatively low each year ranging from 26% to 32% across all years. We observed a negative effect on site occupancy with survey sites located in the Adirondack ecozone of New York. We additionally found support for a negative effect of median elevation and a positive effect of area of hay and pasture on site occupancy within 675 m of survey sites. The probability of a site becoming colonized ranged from 0.05 to 0.14 and the probability of a site going extinct ranged from 0.14 to 0.42. Overall, we did not find support for a decreasing trend in site occupancy. The yearly relative abundance estimates and site occupancy estimates were small but did not decrease over time and the dynamic processes did not suggest increasing extinction or decreasing colonization rates. Occupied survey locations may represent some of the most suitable and stable habitat for these birds within the state. Important landscape characteristics of lower elevation and area of hay and pasture may be representative of forest mosaics that include open areas with forest edges at lower elevation, which has been documented in other studies.

Selecting nest sites that provide access to resources and reduce predation risk is crucial to maximizing fitness in breeding birds. Therefore, understanding what habitat features influence nest site selection and nest success is a key component of avian conservation because it allows for identification and protection of habitat that will promote population growth. We examined drivers of nest success in Gosling's Bunting (Emberiza goslingi) by evaluating variables that influence nest site choice and nest survival at 23 nests and an equal number of random, paired, non-nesting locations in a tropical savannah landscape in north-central Nigeria. Gosling's Buntings exhibited a nonrandom nest-placement pattern. Nests were either on or in proximity to large rock surfaces with nesting probability increasing when the immediate nesting area (100 m radius around the nest) consisted of 30–60% bare rock. Compared to random non-nesting sites, buntings selected areas that were low in litter cover and/or had short grass height. Daily nest survival probability was high (0.96) and was positively associated with the proportion of bare rock around the nest but negatively with the amount of litter cover. Although hatching success was 56.9%, only 30% of all nesting attempts successfully fledged a chick suggesting that nest failure occurred mostly at advanced stages of nesting (nestling phase) when renesting is less likely. Nest survival was higher at low concealment, but only significantly higher than nest failure within a restricted concealment range of 45–54%. Our findings show that microhabitat features could benefit reproduction and daily nest survival. Furthermore, by linking nest-site attributes with fitness indices, we highlight the potential importance of fitness measures as a key component of habitat quality assessment for these buntings in tropical savannahs.

As grasslands have become the most threatened ecosystem in North America, so too have many migratory obligate grassland birds. Chestnut-collared Longspurs (Calcarius ornatus) are a great example, as they have experienced an 89% population decline during the last 5 decades. We captured and tracked individuals during the winters of 2018–2019 and 2019–2020 and calculated their home ranges as both minimum convex polygons (MCP) and fixed kernel density estimates (KDE). Across the 2 winters, we captured and banded 116 longspurs (∼75% males), fitting 90 of them with VHF radio-transmitters. The winter (5 Dec–8 Mar) mean home ranges defined by MCP were 128.8 ha, while the 95% KDE indicated a mean of 29.87 ha. Wintering longspurs used larger areas and displayed higher nomadism than reported for other grassland bird species. Therefore, management for the species scales up beyond the relatively small areas that longspurs aggregate into flocks within and will require landscape-level coordination to maintain habitat adequate for effective winter population.

Barrier islands along the northern Gulf coast provide critical stopover habitats for Nearctic–Neotropical migratory songbirds using a spring trans-Gulf migration strategy. Islands bordering Apalachicola Bay, Florida, project southward into the Gulf of Mexico providing an opportunity for first landfall. In 2013 and 2014, we studied spring stopover ecology on St. George Island, Florida. We provide a detailed description of the arrival body condition and fuel deposition rates of 8 species of migratory birds. We used 3 approaches to measure fuel deposition rate: (1) estimated an hourly rate of mass change by regressing body mass or scaled body mass by time of day, (2) estimated a daily rate of mass change by examining body mass of recaptured individuals, and (3) for 4 species, measured plasma triglyceride concentrations as a proxy of individual refueling rate. The majority of migratory birds in the eastern Gulf of Mexico arrived in poor body condition with depleted fat and muscle stores. We found no significant changes in body mass or scaled body mass as the day progressed, except for Indigo Bunting (Passerina cyanea), which gained mass throughout the day. Recapture rate was low on St. George Island (<5%), but most recaptured individuals tended to lose mass. Using plasma triglyceride concentration, we found that refueling rate for Gray Catbird (Dumetella carolinensis) declined throughout the day. We found no relationship between body condition and refueling rate in Gray Catbird or Catharus thrushes. Our results suggests that long-distance migratory birds arriving on St. George Island after a nonstop migratory flight may be physiologically challenged due to poor body condition. Our results provide the first quantitative assessment of songbird refueling performance on Florida panhandle barrier islands and reinforce the importance of Gulf of Mexico barrier islands as critical stopover sites for long-distance migrants in poor body condition.

Raptor pellets are regularly encountered in the field in a variety of habitats. Where multiple species of similar-sized raptors are sympatric, there can be uncertainty about which species produced a pellet based on visual assessments alone. We developed a DNA barcoding protocol that used environmental DNA (eDNA) to identify birds of prey that had produced pellets. Two different PCR primer pairs were required to successfully ascribe a pellet to the source bird species. Troubleshooting different suspension temperatures and applying multiple primer sets to the same eDNA sample provided sequences that successfully identified Red-tailed Hawk (Buteo jamaicensis) and Great Horned Owl (Bubo virginianus) pellets. Because eDNA degrades, this protocol will only work on pellets that have been in the environment for a limited time, probably <6 months.

Consumption of bats (chiropterophagy) is globally known in 237 bird species. However, bat predation by a non-raptor is rarely observed. Here, we report a predation event by an endemic Malabar Grey Hornbill (Ocyceros griseus) on a Greater short-nosed fruit bat (Cynopterus sphinx) in Western Ghats, a biodiversity hotspot in southern India. This opportunistic record, and other published instances of animal consumption by this hornbill, suggests that such predation activity may be more prevalent during their breeding season.

The Black-necked Crane (Grus nigricol-lis) only breeds in high-altitude wetlands of the Tibetan Plateau. An important breeding area for this species, Qinghai Lake, has recently undergone large water level changes both inter- and intra-annually. Continually rising water between years and rapid rise of water levels during Black-necked Cranes' hatching period led to inundation of eggs. Hatching success among a study population of 13 nests at Qinghai Lake had a mean of 30.77% during 2009–2014. To examine (1) how readily Black-necked Cranes might adapt to artificial nests, and (2) whether artificial nests can improve their breeding performance, we built artificial nests for Black-necked Cranes at Qinghai Lake during 2015–2017. Results showed that Black-necked Cranes adapted well to artificial nests with 16 pairs hatching young in the structures out of 27 attempts, and the occupation rate exceeded 50% in 3 years. Furthermore, cranes using artificial nests had high hatching success rates of 77.78%, 100%, and 72.73%, respectively, and breeding success rate was 11.11–22.22% less than hatching success rate each year. Compared with Black-necked Cranes using natural nests in the study area during 2009–2014, nesting success rate of Black-necked Cranes that used artificial nests during 2015–2017 improved significantly. Therefore, we propose that artificial nests can be used to maintain Black-necked Cranes' nest success rate at Qinghai Lake; our study contributes to the protection of this species in the future.

We documented use of rattle calls when adult Belted Kingfishers (Megaceryle alcyon) approached or departed active nest burrows, and contrasted rattle-call use during incubation and nestling phases of nesting. Adults rattled on 92.7% of 109 nest approaches and 56.2% of 105 nest departures (P = 0.021) combining both phases of nesting. During the incubation phase rattling occurred on 81% of 36 approaches and 28% of 32 departures (P < 0.001), and during the nestling phase rattling occurred on 99% of 73 approaches and 69% of 73 departures (P < 0.001). Overall, a significantly lower amount of rattling occurred during the incubation phase, both when approaching and departing the nest. Males and females exhibited similar patterns of rattle-call use at nest burrows during both phases of nesting. We suggest that use of rattle calls is more prevalent when approaching the nest burrow, despite drawing attention to the nest location, to advertise a mate's or parent's presence prior to entering the burrow and to avoid injury from the tending adult or nestlings defending themselves against an unknown intruder. We also suggest that adults are more secretive near the nest burrow during the incubation phase, especially when departing, because of a reduced need to communicate with their mate while tending the eggs during lengthy bouts of nest attendance. Nevertheless, it remains unclear why adults use rattle calls as much as they do when departing from the nest, which appears to unnecessarily advertise the nest location.

We monitored the emergence of cooperative breeding behavior in 2 Brown-headed Nuthatch (Sitta pusilla) populations that were reintroduced to formerly occupied sites in south Florida. Individuals from presumed family groups were captured and moved (n = 48) in the first reintroduction attempt (1998–2001) on Everglades National Park, Florida, USA. Two cooperative breeding groups were observed in the second breeding season (2000) and the proportion of cooperative breeding groups increased to ∼20% of the territories present in year 5. The second reintroduction attempt focused on capture and release of juveniles (n = 30) onto Jonathan Dickinson State Park, Florida, USA. A cooperative breeding group was observed in the first breeding season (2019) of this second attempt and in the 2 breeding seasons that followed (2020–2021). Cooperative breeding behavior was observed in both reintroduction attempts when nuthatches occupied a small fraction of the available habitat. Habitat saturation has been linked to cooperative breeding behavior in other avian taxa, but our observations point to the potential influence of other factors in promoting cooperation in the nuthatch. Recent studies suggest these factors might include mate limitations, benefits derived from group activities, and direct benefits of co-breeding among >2 adults.

The Cerulean Warbler (Setophaga cerulea), a Neotropical migrant passerine, inhabits deciduous forests across the eastern and midwestern United States and Canada. Within this broad geographic distribution, Cerulean Warbler populations select specific tree species for nest placement and are known to use a variety of deciduous tree species depending on the population. In southern Indiana, Cerulean Warblers typically nest in white oak (Quercus alba), but we have documented 19 tree species used, all of which are deciduous species. During 2018 and 2019, we discovered 2 instances of Cerulean Warblers nesting in pine trees (Pinaceae) in southern Indiana. Our observations suggest that Cerulean Warblers may in some instances select atypical nest sites as long as specific microhabitat characteristics are present at the nest location.

Literature describing the ecology of Montezuma Quail (Cyrtonyx montezumae) is severely lacking. Their unique foraging strategy allows observers to study their foraging habitat selection without capturing them. We located 37 foraging sites in the pinyon-juniper (Pinus-Juniperus) woodlands of Lincoln County, New Mexico, over 2 years and analyzed the data using logistic regression analysis. The mean heights and the mean distances to the closest trees were the most significant factors in foraging site selection. Selection for a site increased by 19% for every 1 m increase in the mean distance to closest trees and decreased by 64% for every 1 m increase in the mean height of the closest trees. These findings support previous Montezuma Quail foraging site selection studies in oak (Quercus spp.) woodlands, which predicted Montezuma Quail select for relatively low (26%) canopy cover.

I present 2 noteworthy foraging observations of a Lesser Yellow-headed Vulture (Cathartes burrovianus) and a Turkey Vulture (C. aura) in Crooked Tree Wildlife Sanctuary and Cockscomb Basin Wildlife Sanctuary, Belize, respectively. I observed a Lesser Yellow-headed Vulture successfully capture a live fish from the water and a Turkey Vulture feeding on feces of neotropical otter (Lontra longicaudis) along a river. To my knowledge, these observations represent novel reports for each species, and contribute to the understanding of the breadth of foraging behavior of cathartid vultures.

The postfledging period is a critical phase of avian life history. In the initial few weeks after fledging, juveniles face various hazards and develop necessary life skills. Knowledge of the postfledging period is important for understanding the fate of juvenile birds. From May to July of 2015, we tracked 22 Gray-backed Thrush (Turdus hortulorum) juveniles from 20 nests in a population in northeastern China using radiotelemetry. Juveniles dispersed from their natal sites for a mean (± SE) of 21.0 ± 2.4 d after fledging. The initial dispersal distance was 560.9 ± 109.4 m (the distance between the natal area and the first postdispersal area). The natal range size of the juveniles had a mean of 1.7 ± 0.5 ha (95% minimum convex polygons). Ten of 22 (45.5%) of the monitored fledglings died within the first 4 weeks after fledging, and predation was the primary cause of mortality. The Cox proportional-hazards regression model showed that there was a positive correlation between tarsus length and the survival rate of fledglings, while the influences of fledgling weight, date of fledging, and brood size on survival were not significant. Our results indicate that mammalian predators were the main threat to juveniles in the first few days after fledging when the juveniles had limited mobility. After the first week postfledging, raptors became the most important source of juvenile mortality.

The relatively new technique of measuring corticosterone (cort) levels extracted from feathers provides a less invasive, more integrated method of assessing a bird's stress physiology. Current understanding is that cort is deposited into the feather via blood when the feather is replaced during molt. The blood supply in the feather is cut off when the new feather completes growth, thereby ending the influx of cort. Previous studies assumed that cort deposited during feather growth remained constant throughout the feather's attachment to the bird, allowing an accurate retrospective index of circulating cort at the time of feather growth. We tested this assumption by measuring cort levels in feathers collected from different wild House Sparrows (Passer domesticus) across 6 important life history stages spanning a single year, thus representing feathers of different ages but grown during similar environmental conditions. If the common assumption is correct, we predicted that feather cort would not vary across the year. We further simulated substantial feather wear by removing the top 20% length of duplicate samples from the same birds across the same time span. We found significant differences in cort levels across life history stages, but no effect of sex or 20% feather removal. After excluding feather wear and sex and re-running the analysis, the effect of life history stage was no longer significant. Furthermore, despite uncontrolled individual and environmental variation, there was not a sustained decrease in feather cort over time. These data support the assumption that feather cort levels are stable while feathers are on the bird, regardless of feather age or typical wear.

The Wilson's Plover (Charadrius wilsonia) occurs along the Atlantic and Pacific coasts from the United States to Brazil, and occasionally in Chile. It is known to breed in the United States, Mexico, Belize, El Salvador, Costa Rica, Colombia, Brazil, Jamaica, the West Indies, and Peru. Outside the United States, we know little about its reproduction and nesting site habitats. On 12 May 2019, we observed a female at a nest with 3 eggs and a separate pair of adults with 2 chicks around the ponds of the Mayasal shrimp farm in Jutiapa, Guatemala. These 2 reports are the first records of Wilson's Plover nesting in Guatemala. Conservation concerns on both breeding and wintering areas include habitat loss, climate change, and human disturbance, as well as a small population size and restricted reproductive range.

I recorded social polygyny in an Eastern Bluebird (Sialia sialis) population located in central Wisconsin. A male simultaneously tended nests with 2 different females at his second and third broods. The polygyny threshold model is not an adequate explanation of this observation. Polyterritoriality cannot be ruled out. Multiple brooding behavior likely created an opportunity for an early breeding male to exhibit social polygyny. Food supplements and breeding asynchrony likely mitigated the costs of sharing a male.

The avian genus Chrysothlypis has 2 species distributed in Central and South America. We report the first description of the nest and breeding behavior of the Scarlet-and-white Tanager (Chrysothlypis salmoni) from the Colombian Chocó. A single nest was found and monitored in March 2018 during a field season in the Anchicayá Valley, Valle del Cauca, Colombia. The nest resembles the nest of congeners in the subfamily Hemithraupinae: a cup constructed with rootlets, leaves, fungal rhizomorphs, moss, and spiderwebs. It was placed 6 m above ground in a Cespedecia spathulata tree located at the forest edge alongside a gravel road. We observed only the female brooding a single chick, but the male helped feed the nestling. Groups of vocal individuals visited the nest and, on one occasion, a suspected helper fed the nestling. Our study presents the first nesting information for this species.

We report the first photographic record of the nest and nestling of the Tepui Swift (Streptoprocne phelpsi) on the top of Mount Roraima, in Venezuela. Two adults and one nestling were observed on a nest in September 2017, at an elevation of 2,630 m, at the entrance of the Cueva del Hotel Guácharos (Ojos de Cristal Cave System), making this the highest record in altitude for the species in the Pantepui region.