A “suture zone” is a zone where geographically otherwise separated faunas meet. New Guinea's Bird's Neck Isthmus potentially constitutes a double suture zone, where the avifaunas of New Guinea's northern and southern lowlands (otherwise separated by the Central Dividing Range), and also the avifaunas of the Vogelkop Peninsula to the west and New Guinea's main body to the east, are in contact. The Isthmus is a north/south corridor only 60 km long and only 160 m in maximum elevation. The watershed lies much closer to the north coast than to the south coast. We surveyed the northern 60% of the Isthmus's interior, previously unexplored ornithologically, to just south of Lake Yamur. We observed 178 species on the Isthmus, including some disproportionately in hilly terrain and others in flat terrain, and identified visually or vocally informative Isthmus populations of 30 geographically variable species. At the middle of the Isthmus, southern forms prevail over northern forms, and both western and eastern forms are represented. At least eight southern populations and one northern population extend across the Isthmus to the opposite coast. We present examples of hybridization, incipient speciation, achievement of sympatry, and ecological segregation. Three species confined to the mountains on the northern watershed descend to or near sea level on or near the Isthmus. We report the first ornithological survey of the waterbirds of Lake Yamur, Indonesian New Guinea's third largest lowland lake.

Wildlife conservation is often improved by understanding the movement ecology of species and adapting management strategies to dynamic conditions associated with movement. Despite a remarkable recovery over the past 30 years, the establishment of self-sustaining populations of California Condors (Gymnogyps californianus) has been challenging in the human-dominated landscapes of southern California. Among these challenges are those imposed by condor ground-foraging behavior that exposes them to environmental contamination. These include lead poisoning from the ingestion of spent ammunition and micro-trash ingestion and, during takeoff and landing, collisions with human structures. We tracked 28 California Condors for 24 months with patagially mounted GPS telemetry units to investigate the characteristics of ground sites condors visited and to identify spatiotemporal trends that might aid in conservation of this critically endangered species. Ground sites occurred on a wide variety of land cover types, primarily on steep slopes, and those more frequently used were associated with open cover. Condors concentrated their visits to ground sites around a 3 h period near midday, and usage increased from winter to late summer. Our study is the first to use remotely sensed telemetry data to describe fine-scale ecological correlates of condor ground-foraging ecology and therefore has important relevance for ongoing conservation and management strategies for this species. The descriptions of ground sites we provide can be used to target conservation or management actions.

Understanding home range size and habitat preferences is an important component of monitoring species in steep decline. Sprague's Pipit (Anthus spragueii) is a declining grassland specialist with a substantial portion of its population wintering in the highly threatened grasslands of the Chihuahuan Desert. We radio-tagged and tracked 10 wintering pipits between 2014 and 2017 at 3 sites across northern Mexico to generate baseline home range estimates and habitat preferences on their wintering grounds. We found that mean home range and core-use area size with 95% and 50% kernel density estimators were 11.4 ha and 2.4 ha, respectively, almost twice as large as some other grassland specialist passerines. Two birds left the study area and one individual shifted its home range 1.3 km after 20 d of monitoring, indicating that some individuals are flexible in their space use strategies. Within their home ranges, pipits selected grasslands with more bare ground and less “other cover” (litter, duff, animal excrement, and rocks) than what was available on the landscape. We found no relationship at the microhabitat scale between pipits and grass height nor shrub cover and heights, which in previous studies have been shown to influence habitat selection at larger scales. These findings may reflect different habitat use, diet, and predator avoidance strategies than other grassland passerines that select for denser grass cover during winter in the Chihuahuan Desert and highlight the importance of structurally heterogeneous grasslands. For this reason, strategies to manage and conserve Chihuahuan Desert grasslands and its avifauna must consider the diverse habitat and area needs of grassland birds to be effective.

The lower Huallaga River in Peru was the focal region of 2 important ornithological collections in the mid-19th century and a third in the early 20th century. Many new taxa were described from these collections, yet the lower Huallaga region has since been largely unexplored by ornithologists. There is a need for modern sampling, including collection of genetic and vocal data, near type localities in order to anchor taxonomic units and better inform conservation decisions. We undertook 2 ornithological expeditions to the lower Huallaga region (Jeberos on the left bank of the Huallaga River in 2001 and Santa Cruz on the right bank in 2016) that collected topotypes or near-topotypes for 18 taxa previously described from the area. We report large range extensions for several species and discuss notable records, taxonomic implications, and biogeographic patterns.

Mountain Plovers (Charadrius montanus) are migratory shorebirds of conservation concern that breed on grasslands and xeric tablelands scattered along the western edge of the Great Plains. Previous research from populations breeding on lower-elevation sites in Colorado and Montana suggests nest survival increases in cooler, drier environmental conditions. However, no studies have estimated Mountain Plover nest survival on high-elevation habitats, which have distinctively different climate and nesting phenology; therefore, it is unclear if these general trends hold true for the species as a whole or are regionally specific. In this study, we monitored nests of a population of Mountain Plovers breeding at high elevation in South Park, Colorado, to study influences on daily nest survival as compared to those found in literature from lower-elevation breeding sites. In contrast to studies on lower-elevation sites where daily maximum temperatures limited nest survival, we found daily minimum temperature best predicted variation in daily nest survival in South Park; survival odds declined with decreasing temperature. These results suggest that negative effects of extreme temperatures (hot or cold) may be generalities that exist between locales but are potentially mediated through different mechanisms at varying temporal scales. Although we cannot definitively conclude from our study why minimum temperature is associated with lower nest survival, we suggest alterations in incubation behavior may be a plausible mechanism that warrants future study. Overall, our study demonstrates the importance of considering differences between weather and phenology among breeding locations when estimating nest survival effects.

Nest predation is the main reason for breeding failure of small passerines. Theory states that predation in the incubation stage should be mostly due to predators finding poor-quality sites, whereas predation in the nestling stage may be driven by parental activity. Yet field evidence for this theory is mixed, and there are few studies from tropical Asia. Red-whiskered Bulbul (Pycnonotus jocosus; RWB) is an abundant generalist species in tropical Asia, often found in human-modified environments. Between 2012 and 2017 in the Xishuangbanna Tropical Botanical Garden, Yunnan, China, we monitored 775 RWB nests, including 287 nests with infrared-triggered cameras, 20 nests with digital video cameras, and 10 with temperature data loggers. The richness of nest predators was high, with at least 11 species, including mammalian, avian, reptilian, and invertebrate species; northern tree shrew (Tupaia belangeri) and Greater Coucal (Centropus sinensis) were the predator species most detected and identified. There was no significant difference in daily predation rate (DPR, as assessed by the Mayfield method) between incubation (DPR = 0.046, n = 682) and nestling (DPR = 0.049, n = 525) stages, even though parental visits in the nestling stage were almost 3 times the number in the incubation stage. Yet during the nestling period there was a strong positive relationship between the parental visitation on a particular day post-hatching (from day 1 to day 10; visitation measured with digital video cameras) and the nest predation rate of that day (measured on all nests). To determine the effect of nest sites on predation, we placed clay eggs in 127 previously used RWB nests. Sites that had been depredated at the incubation stage had marginally higher DPR (0.076, n = 43) when reused than sites that had been successful (DPR = 0.043, n = 50), although this difference was not significant when Bonferroni-corrected. This result thus provides weak evidence for an effect of nest site selection on nest predation. In total, this study emphasizes the strong forces of selection during the nesting period, particularly for birds in human-modified tropical habitats where the diversity of nest predators is high.

Territories provide important breeding and nonbreeding resources for many bird species. Most songbird territory research has been conducted in temperate regions during the breeding season, a situation in which primarily males appear to defend territories and for only a few months. In the tropics, however, both females and males of many species may defend territories year-round and for multiple years, yet few studies have verified this with marked or radio-tagged birds. To assess territory stability in both sexes between seasons and years, we examined similarity in territory size, location, and overlap with neighbors between the breeding and nonbreeding seasons and 2 subsequent breeding seasons in a tropical resident songbird, the Troupial (Icterus icterus). Mated females and males maintained similar-sized, tightly overlapping territories that had considerably less overlap with neighbors than each other. Both sexes maintained similar-sized territories in the breeding and nonbreeding seasons and between years. The location of territory centers and extent of overlap with neighbors was also similar between seasons and years. Divorce and/or territory switching appeared to be uncommon, but upon disappearance of a mate, both sexes often replaced the mate to maintain the territory. Our work quantitatively verifies for both sexes the year-round territorial behavior expected for this and many tropical species. Such territory similarity and stability likely plays a role in song, plumage, and sex role similarities also seen in female and male Troupials.

We describe the breeding biology of the Yellow-browed Tyrant (Satrapa icterophrys) in a native forest of central eastern Argentina. We monitored 23 nests during 3 consecutive breeding seasons (2015–2018). The breeding season lasted from mid-October to late January and all nests were built in native tree species. Modal clutch size was 3 eggs, incubation period was ∼15 d, and nestling period lasted ∼16 d. Daily nest survival rate was 0.96, and the cumulative probability of nest survival in a nesting cycle was 26%. Our data contribute to the knowledge of the life history traits of south temperate bird species. As the Yellow-browed Tyrant only nested in native trees close to temporal or permanent water bodies, we highlight the importance of preserving this type of native habitat which is under threat as a result of overexploitation and development.

I sought to distinguish between sexes and age classes of the Eskimo Curlew (Numenius borealis), as well as to clarify the historical migration pathways and breeding distribution of the species. Discriminant function analysis revealed that sexes significantly differed in bill and tail length, with bill length the best predictor of sex. I found no significant seasonal discrimination in measurements among individuals, nor did I find any difference between early and later Northeastern fall migrants (i.e., primarily adults vs. primarily juveniles). Breast marking shape and extent of white on throat were uncorrelated with other plumage characteristics, whereas pale abdomens and wide, paler margins of wing covert feathers correlated with low density of breast markings. Individuals with pale abdomens and heavily spotted backs also had wide margins of wing covert feathers. Back spotting was the only significant plumage character related to sex, with heavy spotting predominating among females and light spotting predominating among males. I found few clear seasonal differences in plumage among specimens, although dorsal ground color may have averaged darker on spring specimens. Moreover, more lightly back-spotted individuals tended to occur in later fall, which suggested that these birds were juveniles. The existence of individuals with few Y-shaped breast markings appeared to represent one end of a range of plumage conditions that exhibited no clear relationship to age, sex, or geographic location. Mapping locations of museum specimens clarified details of migration pathway extent, provided evidence of migratory concentration spots, and provided additional evidence that Alaska once possessed a breeding population. Examining dates of last collection indicated that populations collapsed below levels at which birds were regularly located after the first decade of the 20th century.

Color aberration in birds is a common biological phenomenon relative to other vertebrates. To date, a large number of avian species with abnormally colored individuals have been documented. Although evidence has shown that color aberration may co-vary with morphological and physiological traits, little information is available on the variations of morphological and physiological traits of free-living aberrantly colored birds. Here we report a case of a free-living female Eurasian Tree Sparrow (Passer montanus) with bleached bill but normally pigmented plumage. We further compare the differences in 5 morphological indices including body mass, body condition index (BCI), length of the bill, tarsus, and wing, and 14 physiological indices including core temperature, hematocrit (Hct), baseline plasma glucose (GLU), total protein (TP), uric acid (UA), total cholesterol (TC), triglycerides (TG), free fatty acid (FFA), beta-hydroxybutyrate (β-HB), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and creatinine (CREA) between the aberrant individual and other normal birds. Our results show that the aberrant sparrow has significantly shorter tarsi, longer wings, and higher core temperature, lower levels of plasma TP, UA, LDL-C, ALP, and CREA than normal sparrows, while no significant differences were noted in other morphological and physiological indices between the 2 phenotypes. Our results indicate that bill-color aberration in the Eurasian Tree Sparrow may be associated with a few morphological and physiological alterations, especially in terms of thermoregulation and protein metabolism. However, these alterations do not result in dramatic changes in body condition, other plasma metabolites, or enzyme activities.

Nomadism in birds is characterized by inconsistent and unpredictable migrations to breeding or nonbreeding areas often related to changing prey conditions. The Ferruginous Hawk (Buteo regalis) has been described as nomadic in studies that documented fluctuations in breeding territory occupancy and synchronous changes in prey abundance. However, documentation of tracked individuals engaged in nomadic movements is lacking and is important for evaluating population status. Between 1999 and 2014 we studied repeatability in patterns of interannual range occupancy and migration of radio-tagged, breeding adult Ferruginous Hawks (n = 33). We computed repeatability coefficients to test individual fidelity to seasonal ranges and migration paths, and timing of migrations among range-wide populations over multiple years (range = 2–6 yr). Hawks exhibited dramatic seasonal differences in annual repeatability of individual movements. During the post-breeding period in late summer, repeatability coefficients for annual range occupancy and migration path fidelity were low (r = 0.37), only 50% of hawks showed range fidelity, and hawks occupied multiple ranges (x̄ = 1.5 ± 0.2 ranges/yr). In contrast, repeatability was moderate to high (r ≥ 0.65) in the breeding season and winter, 83% and 87% of hawks showed range fidelity to respective ranges, and hawks occupied an average of one range each season. All hawks returned to the same breeding region each year. Variation attributed to differences between individuals was significant for most migration characteristics, providing evidence for flexibility within the species for individuals to adapt to different situations and conditions, but with each individual tending to follow the same patterns over multiple years. Seasonal nomadism in Ferruginous Hawks was limited to the post-breeding period in late summer, and we found no evidence for systematic nomadism in spring migration of Ferruginous Hawks that would confound interpretation of breeding population trends. However, we recommend further telemetry studies to simultaneously document migration repeatability for this species prior to and during dramatic prey declines.

Lack of information about basic life history traits of endangered species hinders conservation efforts, since such data have important implications for species' long-term survival. Little is known about the reproductive biology, ecology, and behavior of the Araripe Manakin (Antilophia bokermanni), despite its highly threatened status in Brazil. In this study, we provide detailed information about the Araripe Manakin's breeding biology and discuss ecological factors that affected nest survival rates across 3 breeding seasons. Females lay 1- or 2-egg clutches and may attempt renesting if the nest fails. The open-cup nests are built in the forking branches of 14 different identified plant species. The Araripe Manakin's nesting period corresponds to the rainy season of approximately 6 months, and its annual reproductive capacity is 2 fledglings. Nesting success of the species was high (72%) compared to other Neotropical species with similar nests, but varied across seasons and sampled areas. Fewer nests were associated with periods of less rainfall, more fragmented forest areas, and areas with higher rates of human activity. The shape of the nest also seemed relevant for nest success, where external diameter of the nest appeared to play an important role. Only females provided parental care in all nesting stages and no differences were found in parental investment between nests with 1 or 2 nestlings. We believe our findings are crucial for future population viability analyses and effective conservation strategies. We argue that although these results point toward this species' critical situation, they also suggest its intrinsic resilience.

Waterbird species face numerous threats and many are declining globally, but knowledge of distribution, abundance, and trend remains poor for many species. Five species of marsh-nesting colonial waterbirds are poorly monitored in Canada, and especially so in the core of their range in the Canadian Prairie Provinces (Alberta, Saskatchewan, and Manitoba). We summarized published and unpublished data on abundance and distribution of breeding colonies of Western Grebe (Aechmophorus occidentalis), Franklin's Gull (Leucophaeus pipixcan), Black Tern (Chlidonias niger), Forster's Tern (Sterna forsteri), and Black-crowned Night-Heron (Nycticorax nycticorax) in Alberta, Saskatchewan, and Manitoba. We also examined the degree of overlap in nesting phenology (egg dates) and summarized survey methods that have been used to monitor the species during the breeding season—information that may be useful for the development of a multispecies monitoring program. For all species, the largest number of records of breeding colonies occurred in Alberta, with records declining eastward through Saskatchewan and Manitoba. We identified a number of breeding colonies occurring outside of currently defined species ranges, especially for the poorly studied Forster's Tern. Of 137 waterbodies hosting a colony of at least one species over the past 10 yr, 57 (41.6%) hosted colonies of at least 2 species, and 3 (2.2%) hosted colonies of all 5 species. Species tended to be reasonably synchronous in their breeding phenology, but Franklin's Gulls and Black-crowned Night-Herons tended to initiate nesting slightly earlier than the other species. We conclude that a multispecies survey timed in late May or early June to count nests and/or incubating adults, using either ground-based or aerial surveys, would likely be the most appropriate for monitoring all species jointly in the Prairie Provinces. The approach we take to compiling data from multiple sources on species occurrence and breeding phenology may be applicable to others wishing to examine the feasibility of a multispecies monitoring plan.

Low mate fidelity and return rates are common in many migratory bird species. These low rates are likely due to high mortality during migration, making it impossible for between-year mate reunion to occur. Historically, the majority of return rate studies focused on long-distance migrants. We chose to study Eastern Bluebirds (Sialia sialis), a partially migratory and socially monogamous thrush, to better understand how variation in migration affects the evolution of breeding systems and mate choice. We monitored 59 pairs of Eastern Bluebirds across 4 breeding seasons to determine their return and reunion rates. We also examined the relationship between nest success and mate fidelity. Our data indicate that Eastern Bluebirds have high return and reunion rates. Many of the bluebirds that mated together in previous breeding seasons appear to not only reunite the next year, but they also return to the same territory and nesting cavity. Our results differ from previous findings on Eastern Bluebirds and stress the importance of replication in ecology and ornithology.

The understory has received little attention in studies of tropical forest birds. However, the growing use of camera traps for the study of vertebrates such as mammals has prompted studies on the diversity of terrestrial birds or birds with limited flying capacity. In this study we present an analysis of the diversity of understory birds in a perennial tropical forest of the Chimalapas region, in southeastern Mexico. We collected 967 independent bird records comprising 10 orders, 15 families, 22 genera, and 27 species with a total sampling effort of 8,529 trap-days. The effective number of species indicated the presence of 31 species while Clench's species accumulation model indicated 32, suggesting that over 15% of the species remain to be recorded. Although we did not register all the species potentially present in the understory, bird diversity was higher than in other studies using camera traps. Crax rubra, Tinamus major, and Geotrygon montana were the most abundant species recorded. We obtained records for small-sized (Anthracothorax prevostii, Leptotila plumbeiceps, and Zentrygon albifacies) and migratory (Hylocichla mustelina) species, highlighting the potential of camera traps for their study.

Hybridization between Cerulean Warbler (Setophaga cerulea) and Northern Parula (Setophaga americana) has been suggested from field observations at several sites in eastern North America, but without quantitative data to confirm this pairing. Here we present the first mensural and molecular evidence to confirm hybridization of these closely related species. Two suspected hybrids were detected based on atypical songs during the 2014 and 2015 breeding season in Summit County, Ohio, USA. Analysis of tissue samples, morphometric and plumage data showed a combination of Cerulean Warbler and Northern Parula plumage characteristics; the overall appearance resembled a Cerulean Warbler male but with white eye arcs, a weak yellow wash on the breast, and some yellow mantle feathers suggesting Northern Parula parentage. A mitochondrial and 2 nuclear genes were sequenced. Both individuals' mitochondrial sequences were identical to Cerulean Warbler sequences, indicating that both had a Cerulean Warbler dam. Sequences from nuclear genes had a total of 10 heterozygous loci, confirming that they were sired by Northern Parulas. These hybrids, and other reports, come from areas where Northern Parulas are expanding their breeding range into Cerulean Warbler range, suggesting that this hybrid combination may become more common.

We present observations of breeding behaviors exhibited by a bilateral gynandromorph Eastern Towhee (Pipilo erythrophthalmus) in Rhode Island during June and July 2017. The individual had the black plumage of a male towhee on the left side of its body and brownish plumage of a typical female towhee on the right side of its body. We observed this individual moving with, interacting with, and feeding fledged young. We also recorded the bird singing in similar locations over a 35 day observation period. This is one of the first observations of a free-living gynandromorph bird exhibiting certain breeding behaviors such as associating with another adult, singing, and feeding young.

The identities of avian nest predators remain unknown in many systems. The Mountain White-crowned Sparrow (Zonotrichia leucophrys oriantha) is a high-elevation ground-nesting passerine for which only 4 of 15 suspected nest predator species have been confirmed. In this short communication, we confirm 2 previously suspected but unverified nest predators of Z. l. oriantha that were video recorded during the 2016 and 2017 summer breeding seasons. These nest depredation events include a golden-mantled ground squirrel (Callospermophilus lateralis) in 2016 and a long-tailed weasel (Mustela frenata) in 2017. Both predators were recorded removing nestlings.

Interspecific feeding is an uncommon yet widespread phenomenon where an individual of one species feeds the young of another. There are numerous hypotheses to explain why this behavior might occur, but in most cases the observer can only speculate on the cause because they lack information on the nesting histories of the species involved. We observed a color-banded male Eastern Bluebird (Sialia sialis) feed 10-day-old Tree Swallow (Tachycineta bicolor) nestlings in a paired nest box 29 times during a 3 h nest observation. The male bluebird had previously fledged young from the box where the Tree Swallows were currently nesting and currently was nesting in the paired box, suggesting that the probable cause for this reproductive error was both the close proximity of the box and an attachment to the box where he had previously raised young. This observation suggests that instead of identifying the young by call, the male was using a place-based decision rule when he responded to the calls from the box where he had previously nested. Pairing nest boxes, a common practice used to reduce competition for nest boxes between bluebirds and Tree Swallows, may inadvertently increase the probability of interspecific feeding as a result of location-based decision rules for feeding and care of young.

The level of extra-pair paternity (EPP) is extremely variable among avian species. Although a powerful interspecific database has been provided, further extra-pair paternity investigations on different species and populations in different environments are needed to advance our understanding of avian mating systems. Two passerine species living in same desert environment, the Isabelline Shrike (Lanius isabellinus) and Saxaul Sparrow (Passer ammodendri), are socially monogamous, but exhibit differences in many traits. We identified 6 polymorphic microsatellite loci for the Isabelline Shrike and 10 loci for the Saxaul Sparrow to estimate the rate of EPP. The results indicated that 4.92% of Isabelline Shrike broods (3/61) contained extra-pair offspring, with 1.46% of nestlings (3/ 206) being sired by extra-pair mates. Of the Saxaul Sparrow, 38.82% of broods (33/85) had at least one extra-pair offspring; the percentage of extra-pair offspring was 11.22% (44/392). In conclusion, these 2 passerines have different levels of EPP; however, these levels are comparable to those found in congeneric species.

Although raptors are known to be among the predators of the squirrel monkey (Saimiri spp.), there is little specific information concerning this interaction. In this short communication, we report the use of a common squirrel monkey (Saimiri sciureus) as a food resource by a Great Black Hawk (Urubitinga urubitinga). Beyond aggregating useful information on the natural history and ecology of both the squirrel monkey and the Great Black Hawk, we also highlight that squirrel monkeys are, on average, heavier than the mammals most commonly consumed by Great Black Hawks.

Brood parasitism of Hooded Warblers (Setophaga citrina) by Brown-headed Cowbirds (Molothrus ater) has been well documented, but brood parasitism of this host by other bird species has not been recorded. Hooded Warblers are known to abandon nests with parasitic eggs early in the egg-laying phase, but are not known to remove parasitic eggs from their nests or to replace these foreign eggs with their own. In June 2017, a Hooded Warbler nest in northeastern Pennsylvania was observed to contain a cuckoo (Coccyzus sp.) egg. Within a span of 6 days, the cuckoo egg was gone and a third Hooded Warbler egg was observed in its place.

Introduced and invasive species are emerging as a significant threat to biodiversity, especially to endemic species, worldwide. One of the ways in which introduced species might impact native species is through competition for space, mediated through interspecific interactions. The Red-whiskered Bulbul (Pycnonotus jocosus) is one such species that was introduced to the central Nicobar from mainland India in the late 1800s. Several bird studies from the region postulate that it may pose a serious threat to the endemic Nicobar Bulbul (Ixos nicobariensis). In this study we explored broad patterns in habitat-use intensity of these 2 bulbuls using point counts. Further, we conducted playback trials to assess the nature of their interspecific interactions. Our results show that these 2 species show segregation in habitat use. The Nicobar Bulbul is a forest-dwelling species showing preference for primary forests, while the Red-whiskered Bulbul occurs in the secondary habitats around human habitation. Further, the playback experiments failed to yield any interspecific response indicating a lack of interspecific aggression. We believe that both species, being evolutionarily distinct, naturally segregate themselves on the currently available habitats on these islands. However, destruction of primary forest for plantations and infrastructure development might be a more immediate threat to the endemic Nicobar Bulbul.

Bird entanglement in plants is a relatively uncommonly documented occurrence, with only a handful of plant species known to recurrently trap birds and cause mortality. Here I describe a large number of bird entanglement events, including 3 confirmed bird deaths, involving Boerhavia torreyana (Torrey's spiderling) in an arid canyon in northern Arizona. Like many species of Boerhavia, B. torreyana possesses sticky rings on its stems that are hypothesized to enhance herbivory defense. I document that these sticky rings also frequently capture birds, and identify 39 separate bird entanglement events involving at least 9 different bird species in a small area where B. torreyana is common. Because B. torreyana is an annual plant that germinates with the arrival of the Southwestern monsoon in mid-summer, it matures and presents an entanglement risk at a time that coincides with the fall bird migration. Small ground-dwelling passerines and insectivores appear to be particularly at risk of being trapped. There are very few known examples of plant species that regularly causes bird entanglement and associated mortality, and the observations presented here document a new case of this phenomenon.

We confirmed a new nest predator for the Mexican endemic and endangered Sierra Madre Sparrow (Xenospiza baileyi). We found a Mexican dusky rattlesnake (Crotalus triseriatus) preying on three 6-day-old nestlings while their parents and a neighboring sparrow showed active defensive behavior. We also identified C. triseriatus as a new bird nest predator.

Gould's Wild Turkeys (Meleagris gallopavo mexicana) are the least-studied subspecies of Wild Turkey. Restoration efforts to establish sustainable populations of the subspecies continue throughout portions of the historical range in New Mexico and Arizona. Wild Turkey population viability is driven by reproductive success, yet information on aspects of the reproductive ecology of Gould's Wild Turkey is either scant or nonexistent. We used GPS telemetry to detail reproductive ecology of 23 females during 2017 in southeastern Arizona. We observed a nest initiation rate of 65% and nest success of 58%. Average estimated date for the onset of laying for initial nests was 17 May, which was later than for other subspecies of Wild Turkey. Estimated clutch size (x̄ = 5.6 eggs) across 14 nests and vegetative characteristics at nests were comparable to nest sites selected by Eastern and Rio Grande subspecies, but did not appear to influence nest fate. Mean size of incubation recess ranges was 21 ha (SD = 99), but was highly variable across individual females and we found no evidence of habitat sampling by female Gould's Wild Turkeys before initiating laying of eggs. Females used open/herbaceous habitats and pine-oak woodlands throughout the reproductive period but type of conditions used varied between the laying, incubation, and brooding period. While based on 1 year of field data, our work represents the only assessment of the reproductive ecology of the Gould's Wild Turkey in the United States and should prompt further investigations into the biology of this iconic southwestern species.

We tested whether Eastern Bluebirds (Sialia sialis) avoid nest cavities containing the odors of potential nest predators: the northern raccoon (Procyon lotor) and the house mouse (Mus musculus). In our first experiment, we applied either raccoon urine or white vinegar to partially completed bluebird nests and recorded whether the bluebirds continued nesting or switched to an empty nest box 10 m away. We restricted our analyses to cases in which the nest start was no more than 50% complete at the time we applied the odor. We found no difference in the propensity of bluebirds to switch nest sites in response to urine versus vinegar. Indeed, the vast majority of bluebirds continued nesting in the box into which we added an odor, suggesting that either bluebirds do not associate the odor of raccoon urine with a significantly increased probability of nest predation or that they perceive a nest box 10 m away as being no less threatened. In our second experiment, we presented bluebirds with a choice of 2 identical nest boxes, one containing clean (unused) mouse cage bedding and the other containing bedding soiled with mouse urine and feces. We concealed the bedding in both treatments under cardboard discs to eliminate visual cues and to force bluebirds to rely on their olfactory abilities. Although we used different volumes of cage bedding in the 2 summers, we found no difference between years in the propensity to avoid soiled bedding: bluebirds showed no sign of avoiding soiled bedding at all.

Here we documented brood parasitism by the poorly studied Whistling Hawk-Cuckoo (Hierococcyx nisicolor) on the Rufous-bellied Niltava (Niltava sundara). We describe new information on egg size and incubation and nestling periods for Whistling Hawk-Cuckoo as well as a novel observation regarding cuckoo nestling and host interaction. Whistling Hawk-Cuckoo chicks displayed a vivid-colored gape when host parents were provisioning food. In addition, Whistling Hawk-Cuckoo chicks displayed bright yellow wing patches to their host parents. We observed that host parents tried to place food onto the wing-patch of the nestling instead of into its mouth. We suggest that chicks displaying such wing patches mimicking nestling gapes might be a common strategy for some brood parasite species of the genus Hierococcyx. This behavior also likely occurs in 2 other cuckoos in this genus, H. pectoralis and H. fugax. Finally, we suggest that the bright yellow uropygial gland of young nestlings might also function as an extra gape for the period when the young nestling is not capable of displaying the yellow wing patches.

Long-distance migration is energetically costly and often has a significant impact on bird health and condition. Therefore, understanding the health status of birds during long-distance migration is of ecological interest; however, obtaining invasive health measures is not always feasible or practical. Bird feathers can provide information about individual bird condition independent of invasive and expensive blood tests and have been used previously as indicators of condition, even long after the season of feather growth. Here, we investigated this question using 2 migratory songbirds in North America, Western Palm Warblers (Setophaga palmarum palmarum), which have conspicuous white patches on their tail feathers, and Gray Catbirds (Dumetella carolinensis), which have prominent daily growth bars on their tail feathers. Feathers were collected from birds captured on Jekyll Island, Georgia, during their fall migration. From the feathers we quantified the size of white patches on warbler rectrices and estimated growth bar length (as an index of feather growth rate) on catbird rectrices using image analysis. We also obtained 2 measures of bird health for each species: estimates of white blood cell abundance from blood smears (immune status) and size-corrected body mass (body condition). Analyses of feather traits and how they relate to bird health indicated that warblers (n = 42) with larger white patches had significantly higher body condition indices, although no association with white blood cell abundance, and catbirds (n = 27) with faster feather growth had significantly lower white blood cell abundance, but no association with body condition. Given the utility of these feather characteristics, our results suggest these metrics can be used to provide some insights into the biology of songbirds during one of the most critical portions of the annual cycle, migration.

Birds react to capture, restraint, and handling by both innate physiological and behavioral means, which function to promote survival. Following capture, small birds are typically placed into holding bags for transport and restraint before data collection and/or banding. We examined physical characteristics of holding bags constructed from opaque cotton cloth or polyester mesh and measured behavioral responses of adult breeding Eastern Bluebirds (Sialia sialis) during a 20 min holding period in each bag type, and corticosterone levels at the end of restraint. Bags differed in thread count, percent internal temperature change, and light transmittance, but not in cloth thickness or CO₂ permeation. Birds held in mesh bags struggled and vocalized more over the 20 min holding period and had higher corticosterone levels at the end of the holding period than those held in opaque cloth bags. All birds, regardless of type of bag used to restrain them, returned to feeding their young within 30 min of release and none abandoned their brood. Research involving vertebrate animals ethically and legally requires the refinement of methods to reduce pain or distress. The results of this study suggest bag characteristics influence acute responses associated with capture and thus should be considered when designing capture and holding protocols and interpreting capture-induced corticosterone levels and behavioral responses.

Cooperative breeding is characterized by reproduction in the presence of helpers. What impact these helpers have on the reproductive success of group members is one of the long-standing questions in the cooperative breeding literature. In cooperative species, helpers are known to provide benefits during multiple stages or at a particular stage of the reproductive cycle. The aim of this study was to investigate whether helpers increased the daily survival rate of nests during the incubation stage in the Southern Lapwing (Vanellus chilensis), a crested plover with a cooperative breeding system. Southern Lapwings have a variable mating system, with some breeding groups composed of unassisted pairs, and others that breed in the presence of helpers. Our best-supported model indicated a positive effect of the presence of helpers on the daily survival rate of nests, leading to a probability of nest success (i.e., survival until hatching) of 83%, compared to 51% for nests of unassisted pairs. But a null model had a similar model weight as the best-supported model and was the second-best model. Our study provides evidence that helpers influence egg survival during the egg incubation stage, which could influence the fitness of breeders.