Micro-endemic species are at greater risk of extinction because of their small populations and limited distribution. We conducted a breeding population survey of 3 little-known Mexican endemic bird species: Rose-bellied Bunting (Passerina rositae), Cinnamon-tailed Sparrow (Peucaea sumichrasti), and Orange-breasted Bunting (Passerina lechlancherii) in Sierra Tolistoque, Oaxaca. The purpose of the survey was to (a) determine the population density and size of these 3 species in the Sierra Tolistoque, (b) estimate the relative importance of various landscape features for each species, and (c) provide more rigorous scientific information to aid in the conservation and management of these species. In the case of Rose-bellied Bunting, we aimed to assess whether it prefers ravines over other landscape types during the breeding seasons, as stated in previous studies. Between late May and June 2012, we conducted point counts (n = 209) throughout the southern slope of the Sierra Tolistoque on the Pacific slope of the Isthmus of Tehuantepec, in Oaxaca, Mexico. Overall bird density was 0.98 birds/ha for Rose-bellied Bunting, 0.547 birds/ha for Orange-breasted Bunting, and 0.514 birds/ha for Cinnamon-tailed Sparrow. The estimated population in each landscape category showed that despite the existence of subtle interspecific preferences, hillsides are the major reservoirs for the 3 species. Rose-bellied Bunting did not occur in greater density in ravines compared to hillsides, which comprised more than twice the area of ravines. The importance of the Sierra Tolistoque for the long-term conservation of the 2 micro-endemic species is crucial considering our population estimates suggest that ∼30% of the estimated world population of Rose-bellied Bunting and Cinnamon-tailed Sparrow are found within the range of the Sierra Tolistoque.

Habitat type can dramatically affect wildlife by influencing availability of resources (such as food) or behavior, which in turn can impact reproductive output. Human-dominated areas with short grass, such as golf courses, can provide habitat for wildlife but may have reduced arthropod abundance, which can lower habitat quality for birds. We investigated food availability, foraging behavior, and reproductive success of Eastern Bluebirds (Sialia sialis) nesting in areas with relatively short grass (primarily golf courses) and in nearby fields with taller grass (natural areas) in Wisconsin, USA. We found that areas with shorter grass had significantly lower arthropod biomass. When foraging, bluebirds made more successful prey captures at sites with short grass, but individual foraging success did not influence fledging success or number of broods. Overall, no differences were found between areas with short grass and tall grass in terms of the number of eggs laid or young fledged. The results of this study suggest that despite having lower food abundance, mowed areas with short grass, such as golf courses, can potentially provide valuable habitat for bluebirds.

On the Missouri River, the federally endangered interior population of Least Terns (Sternula antillarum) historically nested on sandbars created by sediment deposited during high flows. The Missouri River has been dammed and regulated, however, resulting in decreased flooding and sediment deposition and thus decreased sandbar habitat. In 2011, unusually high water releases created extensive sandbar habitat on the Gavins Point Reach of the Missouri River, and from 2012 to 2014 we examined the post-flood demography of Least Terns. We monitored 382 nests, uniquely marked 672 chicks, and attempted to recapture chicks every 3–4 d until fledging (∼18 d). Daily nest survival was high (0.99 [SE 0.002]), resulting in high mean nest success (0.87 [0.03]). Nest success was highest in 2012 and declined slightly each year. Daily chick survival was 0.96 (0.01), resulting in a mean survival to fledge of 0.44 (0.08). Daily chick survival did not vary by year or by age of chicks but was negatively correlated to hatch date. Similar to another sandbar nesting species, the federally threatened Piping Plover (Charadrius melodus), Least Terns were highly productive on sandbars created by flooding on the Gavins Point Reach of the Missouri River. Least Terns may have taken advantage of newly created sandbars with similarly high reproductive output to boost and maintain population levels.

Former landfills have long been recognized as a potential source of early successional habitat for wildlife, but their use by migrating grassland and shrubland songbirds has yet to be studied. We estimated mass change rates of 5 grassland and shrubland songbird species during autumn stopovers at a reclaimed landfill in New Jersey, to assess the quality of a former landfill as a stopover habitat. We also examined minimum length of stay, age ratios, and age differences in body mass and fat scores. Regressions of capture time and body mass were statistically significant and indicated gains of 0.8–1.2% of average body mass per hour in Savannah Sparrows (Passerculus sandwichensis), Lincoln's Sparrows (Melospiza lincolnii), and Palm Warblers (Setophaga palmarum), but coefficients of determination were weak (<0.06). White-crowned Sparrows (Zonotrichia leucophrys leucophrys) and Indigo Buntings (Passerina cyanea) did not gain significant mass. Minimum length of stay based on recaptures ranged from an average of 4.7 d in Savannah Sparrows to 10.1 d in Indigo Buntings. Adults did not have higher mass gain rates, body mass, or fat scores than immature birds in any species, with the exception of adult Savannah Sparrows being heavier than immatures in 1 year. The age ratio was significantly skewed toward immatures in all species except the Indigo Bunting, in which the opposite pattern occurred. Food availability at our site may have been poor, limiting the ability of birds to gain mass, or possibly time is not as important to these species at this stage of their migration as energy minimization and predator avoidance are. Considering the low temporal pressure and slow pace of autumn migration relative to spring, these autumn migrants might be using the landfill for rest, energy maintenance, and predator avoidance more so than rapid and substantial fuel deposition. The independence of mass change rate and energetic condition from age suggests that any potential age differences in dominance or foraging ability in these species do not affect their ability to refuel during stopover.

Wetlands under moist-soil management are managed using disturbance and water regimes to enhance vegetative production during the growing season and flooded in the fall to accommodate waterfowl; however, little research has investigated the use of such wetlands by secretive marsh birds. Our objective was to determine patterns of habitat use by bitterns (Ardeidae) and rails (Rallidae), “secretive marsh birds,” in relation to habitat structure within and among moist-soil wetlands during spring and fall migration in Kansas. We used call-playback (spring) and flush counts (fall) to survey birds. Of our target species, only American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Virginia Rail (Rallus limicola), and Sora (Porzana carolina) were detected. Abundances varied markedly between years of our study (2014 and 2015), perhaps because of annual variation in precipitation or drawdown timings. In spring, Sora were found in wetland units with relatively tall Polygonum. No other significant habitat-use patterns were found for other species among wetland units in spring or for any species during fall migration. At the microhabitat scale (within wetlands) during fall, American Bittern and Sora were detected at points of less bare ground, lower grass cover, and greater water cover and depth than systematic sampling points along survey transects. American Bitterns were detected in microhabitats with higher cattail (Typha spp.) cover and height than Sora locations or systematic sampling points along survey transects. Sora were detected in microhabitats with greater Polygonum spp. cover and height and deeper water than American Bittern locations or habitat sampling points along transects. Among years and within wetlands, marsh birds in moist-soil managed wetlands were associated with thick standing vegetation and water, which are likely affected by drawdown timing.

Many birds that breed in mature forest are known to use early successional habitat to some extent during the postfledging period, but the degree of roosting use remains unclear for most species. In fact, for Neotropical migrant passerines, roosting ecology on the breeding grounds is largely undescribed. To determine female Worm-eating Warbler (Helmitheros vermivorum) breeding status, clearcut utilization, and roosting habitat during the breeding season, we attached radio transmitters to 19 female Worm-eating Warblers with fully developed brood patches caught in 8 year old clearcuts from 1 to 15 June 2016. Of the 19 radio-tagged females, 11 were found with dependent fledglings by 17 June: 5 individuals were considered to be independent (i.e., foraging and moving through the landscape without fledglings) and 6 (3 with fledglings and 3 without) to be transitory (i.e., located <5 times before the signal was lost). Nest-searching and telemetry data suggest that the postfledging period may have started by 28 May 2016 for some Worm-eating Warblers. Overall habitat use of radio-tagged female Worm-eating Warblers differed, with 2 individuals associated with clearcut habitat, 3 associated with mature forest habitat, and 8 showing variable use of edge/both habitat classes. We recorded 116 different roost locations for 18 radio-tagged females in clearcut, mature forest, and edge habitats (55, 42, and 19 locations, respectively). Overall habitat preference differed among individuals, but our study suggests that early successional young forest habitat may serve an important role in Worm-eating Warbler roosting and postfledging ecology.

Black-capped Vireos (Vireo atricapilla) and White-eyed Vireos (Vireo griseus) are closely related and ecologically similar. Despite these similarities, the White-eyed Vireo is widely distributed and common, whereas the Black-capped Vireo has a restricted breeding range and is currently federally endangered in the United States and Mexico. Here we address this apparent paradox with a comparative ecological study of co-occurring Black-capped and White-eyed vireos. We studied vireos in shrublands and woodlands in central Texas, USA, in 2013 and 2014. We used point count surveys (n = 256) and nest monitoring (n = 144) to determine arrival dates, settlement patterns, nest site selection, and nest survival relative to temporal and habitat factors. Additionally, we conducted reciprocal playback trials (n = 16) to test for the presence of interspecific aggression. White-eyed Vireos arrived first and established territories in both habitats with equal probability. Black-capped Vireos arrived after White-eyed Vireos and settled in greater numbers in shrubland habitat. White-eyed Vireos initiated nests earlier than Black-capped Vireos and selected nest sites surrounded by taller, more mature, and more densely wooded vegetation. For both species, nest survival declined as the season progressed and was greatest in tall, mature vegetation. Lower nest success in Black-capped Vireos (27% vs. 40%), although equivocal, supports earlier findings and suggests that the flexibility demonstrated by White-eyed Vireos confers a reproductive advantage. Playback trials failed to detect evidence of interspecific aggression, suggesting that competition with White-eyed Vireos is not limiting the Black-capped Vireo.

The breeding biology and natural history of Gray Tinamou (Tinamus tao) is poorly known. Camera traps and artificial feeding stations allowed us to study 2 nests and to observe courtship behavior at Copalinga Ecolodge, Zamora Chinchipe province, southeast Ecuador, between February and August 2014. Nests were shallow depressions in the leaf litter. One adult male incubated 2 turquoise eggs for at least 18 d at one nest, whereas the other nest was depredated. The fledglings and adult abandoned the nest 1 d after hatching. Courtship display included chasing, coordinated movements, soft rolling vocalizations, and mating. Further, we describe plumage development from a few days after hatching to 12–13 week old immature stage and discuss the species breeding biology in comparison to other Tinamidae species.

Females often invest more in parental care than males, but in socially monogamous systems, males invest as much as females in caring for their offspring, and male contribution is believed essential for reproductive success in these systems. Here we describe the number of visits, the feeding rate to their nestlings, and the time on the nest invested by each sex of the socially monogamous songbird, the Clay-colored Thrush (Turdus grayi), for 16 nests in San José, Costa Rica. Both males and females fed their nestlings at a similar rate, but females visited the nests more frequently than males. The feeding rate of both females and males was also similar when controlled by age of nestling. The feeding rate was highly variable across males (minimum 1, maximum 15 visits per 2 h), possibly related to the probability of males fathering the offspring of the attended nest. Females spent more time on the nest than males, but males tended to remain near the nest to defend it from predators. Moreover, male contribution during the nestling period correlated with the reproductive success.

The invasion of exotic grasses is a potential threat to the winter habitat of migratory grassland birds by reducing native sources of seed food. We compared seed preferences among 3 native (blue grama [Bouteloua gracilis], sideoats grama [Bouteloua curtipendula], and green sprangletop [Leptochloa dubia]), and 3 exotic (Lehmann lovegrass [Eragrostis lehmanniana], buffelgrass [Pennisetum ciliare], and natal grass [Melinis repens]) grass seeds in captive Baird's (Ammodramus bairdii), Grasshopper (A. savannarum), and Savannah (Passerculus sandwichensis) sparrows to investigate factors that determine vulnerability of grassland passerines to exotic grasses in the Chihuahuan Desert. We hypothesized that seed handling time would determine the ability of sparrows to exploit exotic grass seeds, and that larger-billed birds would be able to better exploit a larger variety of seeds, including exotic seeds. We offered seeds in choice and nonchoice trials and determined handling times for the different seed and bird species. The results indicate that handling time in relation to seed size determined seed preferences. Sparrows preferred seeds they could handle more efficiently to maximize energy intake over time. Baird's and Savannah sparrows, with intermediate and small bill sizes, respectively, preferred natal grass seeds of intermediate size and short handling time, and Grasshopper Sparrows, with the largest bill, preferred the larger sideoats grama seeds. Lehmann lovegrass, the smallest seed with intermediate handling time, was avoided by the 3 sparrows. Buffelgrass, the largest seed with the longest handling time, was avoided by Baird's and Savannah sparrows. Blue grama, the second-smallest seed with relative short handling time, was neither preferred nor avoided, and green sprangletop, an intermediate-sized seed with a relatively longer handling time, was avoided in the choice trials but consumed in the nonchoice trials. These results indicate that exotic grass seeds may be a source of food for 3 sparrows wintering in the Chihuahuan Desert, provided they can be handled efficiently. Our results also show, however, that wintering grassland sparrows are probably unable to consume sufficient buffelgrass and Lehmann lovegrass seeds to meet daily energy requirements, indicating that these grasses may be a threat by reducing exploitable sources of seed food.

Tropical dry forest is one of the most threatened ecosystems in the Neotropics as a result of agriculture, cattle ranching, and timber extraction. The effects of disturbance on the bird communities of this ecosystem have not been well studied. In this study, we evaluated changes in the richness, abundance, and diversity of birds and their diet types in the following land uses in southwestern Mexico: agroecosystem, palm grove, forest edge, and undisturbed forest. Visual and auditory sampling was performed for 1 year (August 2014 to July 2015) in 40 circular plots with a radius of 30 m (10 plots per land use). Differences in the composition and the abundance of bird species in plots of distinct land use were analyzed by a non-metric multidimensional scaling (NMDS) ordination to determine similarity among the data. In total, 101 species from 29 families were found in the study sites. The agroecosystem presented the greatest species richness (70 species), followed by undisturbed forest (57). Overall abundance of birds differed significantly among land uses. Bird abundance and dominance, in addition to the abundance of diet types, also varied significantly among land uses and between dry and rainy seasons. We found species of open habitats as well as species dependent on undisturbed forest fragments. The results suggest that seasonal variation in the abundance of birds is mainly determined by the availability of food resources and other local environmental factors. The abundance of carnivorous, granivorous, omnivorous, insectivorous, and frugivorous birds was higher at disturbed sites while the abundance of nectarivorous birds was higher in the undisturbed forest. The species composition of the undisturbed forest was most distinct among the land uses. Our results showed that the comparison of diet types was more useful for understanding the effect of land-use changes than the sole evaluation of the structural patterns of bird assemblages.

The genus Turdus has a nearly complete anthology of nesting descriptions for its 70 species. One species yet to have nesting described is Turdus hauxwelli, a Neotropical bird native to South America. In addition to an altitudinal range expansion, here we document 19 active T. hauxwelli nests from 2 elevational regions (400 and 1,350 m) in the Andes of Southeastern Peru. Along with detailed descriptions of nest measurements and composition, we also describe nesting behavior. We present detailed information on T. hauxwelli temperature fluctuations in nest and eggs, and nest attentiveness during incubation and nestling period. The average egg weight was 6.12 g with dimensions of 26.71 × 20.05 mm. The female conducted an average of 28 trips per day during incubation, which lasted 13.7 d while the nestling period lasted 14.25 d. The overall daily survival probability for the nests is 19.5%. Other nesting traits were also similar between sites, with only nest mass differing by 37% between elevations, and even greater at higher elevations. Nesting traits among Turdus species do not vary drastically, however, despite occupying a variety of ecosystems from sea level up to 4,500 m, suggesting a low evolutionary lability in nesting traits in this genus.

Reproductive competition in the form of ovicide is common in some joint-nesting birds, species in which multiple females lay eggs in a single nest. Joint-nesting Smooth-billed Anis (Crotophaga ani) often bury eggs under a new nest floor prior to laying their own eggs. Anis apparently cannot recognize their own eggs, which raises the question of how individuals can minimize their loss of young due to egg burial or consequences of hatching asynchrony. Newly laid eggs are coated with a white layer of vaterite (calcium) while older eggs may be almost entirely blue. Leaving older, bluer eggs in the nest presumably leads to a more competitive nest environment for the female's own young because newer eggs hatch later, producing smaller chicks at risk of getting trampled or bumped out of the nest. We hypothesized that Smooth-billed Anis use egg color as a cue for egg age. We predicted females not yet laying would bury older-looking blue eggs and tested this by removing the vaterite layer from all eggs in selected nests. Contrary to our prediction, altering egg color of whole clutches to make them look bluer, and thus older, did not trigger egg burial. The number of eggs buried increased with increasing female group size, however, consistent with previous work on this species.

Nest failure of most pairs of Roseate Terns (Sterna dougallii) at Falkner Island, Connecticut, in 2002–2003 (due mainly to predation by Black-crowned Night-herons [Nycticorax nycticorax]) was followed by the rapid departure of many of the failed individuals in both years. Nine failed pairs (16.7%) stayed while 40 (74.1%) of 54 unsuccessful pairs left within 2 d following nest failure in 2002, and 7 pairs (21.9%) stayed while 25 (78.1%) of 32 unsuccessful pairs left within 2 d in 2003. Individuals that departed this colony site by the end of June likely had time to prospect and renest at another colony site in the same year, and individuals that successfully renested at another colony site could have shown reduced colony-site fidelity to Falkner Island in subsequent years.

Long-term monitoring of seabird breeding cycles and breeding success is essential for conservation and a valuable indicator of ecological change, but is logistically expensive and time consuming. We describe the annual cycle and year-round colony attendance patterns for Gentoo Penguins Pygoscelis papua at Martillo Island, Beagle Channel, by analyzing camera trap photographs. We deployed a Reconyx HC500 Hyperfire trail camera programmed in time-lapse mode to take single pictures once per hour year-round (27 Feb 2013 until 27 Feb 2014). The nonreproductive stage began 23 April 2013 when adults completed molt and ended 24 September 2013 when the first pair formation was observed. In general Gentoos Penguins performed daily trips, and the number of adults present at 1900 h ART was not significantly different at any stage except the late chick-rearing and premolt stages. Breeding success was 0.92 chicks per nest. Small variations in day length had a significant influence on penguin's trip duration during the nonreproductive stage. The method proved to be effective for monitoring this species and provided important data for management and conservation.

Sources of measurement error using analog thickness gauges include differences in eggshell thickness at the points of measurement, imperfections in the micrometer within the limits specified by the manufacturer, imperfections or contamination of the eggshells, and human error in applying and reading the (analog) instrument. The errors due to using a mechanical instrument can be avoided by using an instrument such as the Magna-Mike 8600 or the MiniTest 7200 FH Hall-effect thickness gauges (HETG), which perform nondestructive measurements of non-ferrous materials by precisely measuring the distance between a small steel reference ball (min 1.59 mm) and a magnetic probe. The difference corresponds to the thickness of the eggshell and membrane (if present) to the nearest 0.001 mm and provides a precise and accurate digital measurement. Measurements at the equator of eggs using the HETG were similar to measurements using the Starrett thickness gauge (i.e., correlation coefficient = 0.946) measuring the same parts of the eggshells but generally measured 0–9% thicker, and overall variation in measurements was similar (coefficient of variation for 750 measurements of 150 eggshells was 15.5% using the HETG and 16.3% using the Starrett). When HETG measurements were compared to literature-reported pre-DDT-era eggshells of Clapper Rails (Rallus longirostris) and Forster's Terns (Sterna forsteri), the HETG measurements were about 12% thicker. Measurements thinner than published values may be due to measurements taken from museum eggshells, which are usually blown-out eggs, so only a small area around or across from the blow-out hole was measured with the analog gauges, whereas the entire eggshell thickness around the equator was measured using the HETG. Each eggshell was measured twice with a Starrett and HETG (using slightly different methods) to determine which measurement provides the most precise, and therefore most repeatable, measurement. I found the HETG to be a useful device that provides accurate and precise measurements without many of the measurement errors of analog mechanical devices, and it can also measure smaller more fragile eggs without damage to the eggshells.

In the breeding seasons of 2014 and 2015, we determined sexual size dimorphism and mating pattern in a breeding population of the Plain Laughingthrush (Garrulax davidi concolor) at Lianhuashan Nature Reserve in Gansu, China. We found that males were significantly larger and heavier than females, with a 104.8 body mass dimorphism index. Positive assortative mating based on culmen length was found across breeding pairs. Male-biased territory defense and mate-guarding suggest that sexual selection may be responsible for sexual size dimorphism in this bird. We also found significant positive correlations of body mass and body temperature between breeding pairs. We propose that this type of positive assortative mating could be a consequence of synchronous breeding by pairs in a similar physiological state.

This paper describes the first case of successful polyterritorial polygyny in the European Blackbird Turdus merula. It was detected in an intensively studied color-banded population of European Blackbirds in Szczecin (northwestern Poland).

Biologists interested in using radio telemetry to track the movements of birds should concurrently conduct studies to assess potential impacts on study organisms, particularly when monitoring threatened or endangered species. We investigated the effects of traditional and digital very high frequency (VHF) radio transmitters on daily nest survival and chick survival rates of Piping Plovers (Charadrius melodus) along the Atlantic Coast in 2012, 2013, and 2015. We attached 1.0–1.2 g transmitters to 110 plovers and monitored their 160 nest attempts. We also monitored 221 nest attempts by 161 control pairs with no transmitters. There was no evidence that nest or chick survival differed between tagged and control pairs. Transmitters did not seem to adversely impact Piping Plover daily nest and chick survival and are a valuable tool to monitor movements of this threatened species.

We present the first description of Common Nighthawk (Chordeiles minor) diet from the boreal biome. Knowledge of diet is important for this crepuscular aerial insectivore, whose population declines may be related to insect food sources. We collected 4 nestling diet samples as food boluses from 1 adult female and 3 adult males on the breeding grounds in northern Alberta, Canada. Coleopterans comprised the majority of samples, and the composition of the sample from the female differed from those collected from males. Further research is needed across the boreal forest to characterize foraging strategies and assess the potential role of food availability in population declines.

The use of video cameras to monitor avian nests has allowed identification of key nest predator species and could potentially improve our understanding of parental nest defense. For songbirds, cameras have often shown snakes to be the most common nest predator, although video evidence of passerines successfully defending nests against snakes is lacking. We describe the first evidence of a small passerine, the Louisiana Waterthrush, successfully thwarting a possible predation attempt by a juvenile ratsnake. This recording documents rarely observed nest defense behavior and allows us to consider how this event fits within theories of optimal nest defense.

In contrast to the thoroughly studied incubation and nestling periods, the postfledging period of the Common Cuckoo (Cuculus canorus) remains virtually unknown. Here, we report detailed observations of a cuckoo fledgling attended by a male Chaffinch (Fringilla coelebs). Molecular data (nuclear DNA) showed the fledgling was a male belonging to the Cuculus c. canorus/C. saturatus clade while mitochondrial DNA data confirmed that it did not belong to blue egg gens that parasitizes Redstarts (Phoenicurus phoenicurus), which is the most common local host and the only regular Common Cuckoo host. During one week of observations, feeding rates did not change, body mass decreased (by 10%), and wing length increased (by 16%). Video recordings showed that the provided diet consisted mostly of larvae and that the fledgling also self-fed on lichens. A radio transmitter fitted on the fledgling revealed that daily movement distances ranged from 0 to 650 m and significantly increased with age. We suggest that future studies should focus on the postfledging period in brood parasite young because this stage currently represents a major gap in our understanding of parasite–host arms races.

The Silvery-throated Jay (Cyanolyca argentigula) is a poorly known Neotropical corvid endemic to the Cordillera de Talamanca of Costa Rica and western Panama. In April 2016, we found an active Silvery-throated Jay nest in Chirripó National Park, Costa Rica. Here we provide the first description of the breeding biology of this species, including nest architecture, estimates of incubation and nestling periods, and observations of adults attending the nest. The large cup nest, placement in the crown of a small tree, and breeding phenology are similar to other Cyanolyca species. We observed up to 5 adults associated with this nest, including at least 3 different adults that fed chicks. These observations suggest cooperative breeding at this nest but are also consistent with the possibility of communal breeding. Future studies with color-banded individuals and genetic sampling will be necessary to better understand what seems to be cooperative breeding in the Silvery-throated Jay.

The endangered Peruvian Plantcutter (Phytotoma raimondii) is a strictly herbivorous, mostly folivorous passerine endemic to the arid lowlands of northwestern Peru. Previous information obtained from the study of 3 of its major populations consistently suggests the selective use of plant material from the shrub Grabowskia boerhaaviaefolia and Prosopis spp. trees; however, our generalized understanding about the relative importance of these plants could be biased. Some of the Peruvian Plantcutter's populations in which these plants are scarce, and even seemingly absent, have been generally overlooked. We investigated resource use for foraging and nesting by Peruvian Plantcutters at one of these locations. We conducted nest searches inside the area and diet selection analysis in 5 territories of mated pairs. We found 7 nests, built almost exclusively of Scutia spicata twigs, a shrub previously reported for another population as a selected food source along with G. boerhaaviaefolia and Prosopis spp. Here, S. spicata was the food source selected by all mating pairs while Prosopis pallida was scarce overall, selected by just one pair and found only within 2 territories. G. boerhaaviaefolia was not detected throughout the sampling area. This study reveals that the Peruvian Plantcutter occupies a wider range of breeding habitats than previously thought; however, its flexibility in resource use is still expressed within a narrow array of known selected plant species.

Documented observations of interspecific nest usurpation are rare and have been observed mostly in cavity-nesting species, where cavities are limiting and competition for them can be strong. We report one of the few known instances of interspecific nest usurpation in the family Parulidae (North American wood-warblers) between the Cerulean Warbler (Setophaga cerulea) and American Redstart (Setophaga ruticilla). During May and June 2016, we observed a female American Redstart usurp and successfully fledge at least one of its young from a nest built by a female Cerulean Warbler in Yellowwood State Forest, Brown County, Indiana. Based on our field observations, we provide information on nest chronology and describe American Redstart adult behaviors at the usurped nest. We hypothesize that this instance of interspecific nest usurpation may have been a result of high local breeding densities of both Cerulean Warblers and American Redstarts in our study area.

Cotingas are considered essentially frugivorous, but a few records suggest they might include small vertebrates in their diet, mainly during the breeding season. In March 2015, we recorded a young male of an Andean Cock-of-the-rock (Rupicola peruvianus) chasing and eating an adult Canada Warbler (Cardellina canadensis) in Santa Maria, Boyacá (Colombia). The next day, we observed another adult male chasing a Swainson's Thrush (Catharus ustulatus), but we were unable to observe the end of the chase. Observations of hunting small vertebrates suggest this species may be omnivorous, not only during the breeding season but throughout its annual cycle. These may be rare cases, but notably both events involved migratory species that may not recognize these colorful birds as possible predators because they are not exposed to cotingas in the temperate zone. Predation on adult birds is difficult to observe in the wild, but this information is essential to better understand the life histories of birds and the different selection pressures acting on them.

Demographic assessments of nesting birds typically focus on failures due to nest predation or brood parasitism. Extreme weather events such as hailstorms, however, can also destroy eggs and injure or kill juvenile and adult birds at the nest. We documented the effects of a severe hailstorm on 3 species of sagebrush-associated songbirds: Sage Thrasher (Oreoscoptes montanus), Brewer's Sparrow (Spizella breweri), and Vesper Sparrow (Pooecetes gramineus), nesting at eight 24 ha study plots in central Wyoming, USA. Across all plots, 17% of 128 nests failed due to the hailstorm; however, all failed nests were located at a subset of study plots (n = 3) where the hailstorm was most intense, and 45% of all nests on those plots failed due to hail. Mortality rates varied by species, nest architecture, and nest placement. Nests with more robust architecture and those sited more deeply under the shrub canopy were more likely to survive the hailstorm, suggesting that natural history traits may modulate mortality risk due to hailstorms. While sporadic in nature, hailstorms may represent a significant source of nest failure to songbirds in certain locations, especially with increasing storm frequency and severity forecasted in some regions with ongoing climate change.

We investigated whether visual cues of a nest predator at the nest site prior to the completion of nest building would induce Eastern Bluebirds (Sialia sialis) to abandon their nesting attempt and switch to another box 10 m away. Upon detecting the onset of nest building in one of the paired boxes, we presented the birds with either a visual predator cue (a rubber black rat snake (Pantherophis obsoletus) or a visual control cue (a model Northern Cardinal (Cardinalis cardinalis) on the active nest box for 15 min and recorded the responses of the resident pair of bluebirds. We returned 1 week later to determine whether the presentation of the snake or cardinal resulted in no change, a switch to the other box, or abandonment of the box pair. Although the bluebirds seemed to respond more negatively to the model snake, we found no significant difference in their propensity to abandon the box pair (vs. remain in one of the paired boxes). We found a similar majority of bluebirds continued to nest in the same box (vs. abandon the effort) in both treatments. Even when we restricted our analysis to the box pair, we found no difference in the propensity to stay vs. switch. Although a larger proportion of bluebirds responded to the snake vs. cardinal model with mobbing, the difference did not reach significance. Bluebirds that mobbed the model were no more likely to abandon the box pair than those that did not mob the model. Although more mobbers abandoned their nest start than did non-mobbers, this difference was not significant. We conclude that the costs of finding a new nest cavity and the close proximity of the boxes provided limited the options of these secondary cavity nesters, even those that engaged in mobbing.