During the last 2 centuries, widespread declines have been observed in migratory species, and these declines have largely been linked to anthropogenic causes. Migrants move across multiple spatiotemporal scales with wide-ranging movements that can cross multiple jurisdictions. Consequently, conservation and management require the incorporation of these wide-ranging movements. However, for many nongame species, basic information on migration and wintering ecology is poorly known. Yellow Rails (Coturnicops noveboracensis), LeConte's Sparrows (Ammospiza leconteii), Nelson's Sparrows (A. nelsoni), and Sedge Wrens (Cistothorus stellaris) represent a diverse avian assemblage that breeds in prairie potholes, boreal forest, and coastal areas of northern and eastern Canada and winters in coastal prairies in the southern United States. We used a stable deuterium isotope (δ²H_f) analysis to assign breeding season locations for individuals captured wintering in the southeastern US. We obtained deuterium values from secondary feathers of birds spending the nonbreeding season from Oklahoma and Texas east to Florida. We found substantial differences in the δ²H_f values of Yellow Rails and Nelson's Sparrows, with birds wintering in Oklahoma and the western Gulf of Mexico having δ²H_f values that were probabilistically assigned to the western half of their breeding range, while birds wintering in Florida were probabilistically assigned to the eastern portion of their breeding range. LeConte's Sparrow breeding season assignments for birds wintering in Texas and Oklahoma overlapped. Sedge Wrens did not exhibit spatial variation in isotope values.

Collisions with tall anthropogenic structures (power lines, wind turbines, communication towers, and buildings) are a regular cause of mortality for nocturnal avian migrants. To better understand relationships between weather and migrant collision risk, we compared nocturnal hourly mean barometric pressure, temperature, relative humidity, wind direction, and wind speed to avian passage rates (targets/km/h) and flight heights during 1 year of spring and fall migrations near a recently reconstructed transmission line crossing Kittatinny Ridge, New Jersey, using 2 marine radars. We found lower spring flight heights associated with decreasing barometric pressures, temperatures, and relative humidity across all wind directions. Spring flight heights showed the strongest decreases with increasing wind speeds for headwinds and crosswinds while flight heights slightly increased with stronger tailwinds. Spring passage rates increased with lower relative humidity and higher temperatures. With increasing wind speeds, spring passage rates declined faster with headwinds and crosswinds, and only slightly with tailwinds. We found lower fall flight heights with decreasing temperatures and relative humidity, but the relationships varied by wind direction. The lowest flight heights occurred under tailwind and crosswind conditions. Increasing fall passage rates were associated with increasing barometric pressures and when wind speeds were lowest. Fall passages rates declined with higher wind speeds but were more gradual under tailwinds and crosswinds when compared to headwinds. Overall, 2–4% of birds migrated under conditions that would have placed them at risk of collision with the transmission lines. Similar studies conducted along migratory pathways could be used to predict nights where birds exhibit low flight heights around other obstacles along their migration path. These predictions could improve detection rates for carcass searches documenting relatively rare collision events. For sites with topographic features likely to concentrate nocturnal migrants, radar studies could be conducted before siting towers so that impacts to migratory birds could be avoided at these sites.

We recovered 12 archival geolocators deployed on Eastern Kingbirds (Tyrannus tyrannus) breeding in New York (NY; n = 3, 2 with 2 years of data), Nebraska (NE; n = 6, 1 with 2 years of data), and Oregon (OR; n = 3) to describe migratory routes, timing and rates of migration, nonbreeding season distributions, and migratory connectedness. NY fall migrants migrated along the Atlantic coast to Florida, flew either nonstop across the Gulf of Mexico (GoM; 2 of 3 birds) or stopped once along the way (Cuba and Cayman Islands in different years) to land in Yucatan/Central America. Fall birds from NE and OR arrived at the GoM in the region of the border between Texas and Louisiana, and most likely took a land route to Central America. In spring, all NY birds flew nonstop across the GoM, and once in North America, took a more inland route than in fall. Trans-GoM flights were more common among NE and OR birds in spring than fall. Birds migrated faster in spring than fall, and in both seasons, late departure was associated with more rapid migration. Migratory connectivity was low, and all birds from OR, and one bird from NE and NY each, occupied a single region in northwestern Amazonia (southern Colombia, northern Peru, and eastern Ecuador) while in South America. Most kingbirds from NE and NY were intratropical migrants, occupying 2 regions for periods of ≥30 d. The latter birds migrated farther south to western Brazil and northern Bolivia, but then moved north to later use the same area in northwestern Amazonia where other birds remained throughout the overwinter period. Northwestern Amazonia thus appears to be a critical area for all Eastern Kingbirds during the nonbreeding season, possibly because a prolonged wet season supports abundant fruit resources.

Eastern Towhees (Pipilo erythropthalmus) are partial migrants that inhabit dense thickets of shrubs in both breeding and nonbreeding seasons and have declined range-wide by approximately 50% since the mid-1960s. Few studies have addressed the nonbreeding season natural history of Eastern Towhees. The objectives of our study were to (1) describe and quantify nonbreeding habitat use and social interactions, and (2) relate these metrics to winter weather conditions. We captured and radio-tagged 9 Eastern Towhees and tracked them using homing and triangulation for a total of 528 locations from late November 2015 to March 2016, plus 3 Eastern Towhees tracked in 2014–2015. The mean (± SE) home range size (80% kernel isopleth) was 7.31 ± 0.22 ha, and the mean (± SE) core area (30% kernel isopleth) was 1.52 ± 0.94 ha. The mean overlap of home ranges between neighbors was 36%, and 24% between neighboring core areas. The study area was classified into 4 habitats: mowed, blackberry scrub, woody shrub, and wooded. Habitat use did not directly correspond with availability: Eastern Towhees occupied woody shrub habitat most (48% of locations vs. 35% of available habitat), suggesting that of our 4 habitat types, woody shrub was preferred. For weather, wind speed did not significantly affect habitat use, foraging method, vocalizations, or flock size. Although temperature did not significantly affect any of the behaviors, there were trends for less ground foraging and more use of wooded habitat in freezing temperatures. Snow cover influenced habitat use (odds ratio = 0.60), vocalizations (odds ratio = 1.77), and flock size (odds ratio = 1.97), but not foraging. These results contribute to understanding the nonbreeding natural history of Eastern Towhees and demonstrate that inclement weather in the nonbreeding season may influence habitat use and behaviors in ways that could affect nonbreeding season survival.

Increased sea-surface temperatures lead to increased egg cannibalism in Glaucous-winged Gulls (Larus glaucescens). Under these conditions, female gulls, which lay an egg approximately every 2 d, can synchronize egg laying with other females on an every-other-day schedule. Eggs that are laid synchronously are less likely to be cannibalized. The mechanism for synchronization has remained unknown. We studied the relationship between egg laying and mounting in a colony of Glaucous-winged Gulls on Protection Island, Washington, for clues to a synchronizing mechanism. We found that for an individual female an oviposition event reduced the likelihood of mounts for that day as compared to the day before, and that for sampled areas of the colony, total numbers of mounts and eggs laid occurred in an out-of-phase rhythm. These findings support the following conceptual model: early in the breeding season, individual females that have begun laying exhibit a daily alternation of higher and lower mounting activity caused by their natural 2 d oviposition oscillation. By social facilitation, these mounting oscillations of early layers synchronize mounting across the colony, including mounting events involving females that are not yet laying. Mount synchronization eventually leads to every-other-day egg laying synchronization.

Nesting is a particularly sensitive period during which birds are highly vulnerable to predation, parasitism, and other natural events resulting in high mortality rates. Some factors can increase nesting success, such as habitat selection. In general, only female hummingbirds build nests, incubate eggs, and provide nestling care until chicks can feed independently. The purpose of our study was to describe nests (shape, size, and construction materials), nest survival, and habitat use of 3 resident hummingbirds in western Mexico: Cinnamon Hummingbird (Amazilia rutila), Golden-crowned Emerald (Cynanthus auriceps; a Mexican endemic), and Broad-billed Hummingbird (C. latirostris). In all 3 species, the nest is an open cup built with plant material and bound together with spider web. All 3 species used the same materials (silk cotton, wood, and grass) for nest construction. However, Cinnamon Hummingbird was the only one that used lichens at its outer surface, whereas Broad-billed Hummingbird used only seeds. We did not find interspecific differences among the materials used and their quantities. A low nest survival (26%) can be explained by the high rate of predation but also by the occurrence of natural events such as hurricanes. All 3 species showed preference for nesting in semi-deciduous forests but chose different nest placement sites that differed in (1) nest height, (2) the height of trees or shrubs where nests were built, and (3) the diameter of the supporting branch within a shrub or tree. Other factors, such as distance to the nearest stream, and distance to nesting-branch tip or trunk, did not differ among species.

To inform the design of targeted, species-specific surveys of Prairie Warbler (Setophaga discolor) in Ontario, Canada, we used autonomous recording units (ARUs) to document patterns in male vocal activity. We deployed recorders within the territories of breeding males at coastal sites near Georgian Bay, and at inland sites near Kaladar, in June 2015 and 2016, respectively. Although coastal and inland sites are <250 km apart, we observed distinct differences in the patterns and frequency of male singing. Overall, the mean number of songs per minute of males at inland sites near Kaladar was nearly triple that of coastal sites near Georgian Bay. Daily singing activity peaked shortly after sunrise and declined throughout the day at both sites. Daily singing activity was uniformly high across the entire morning period at coastal sites, whereas at inland sites the highest rates of singing were during the post-dawn morning period. Singing activity varied by chronological day at inland sites, with distinct peaks at the beginning and end of June. Singing at coastal sites did not vary by chronological day and was consistently low throughout June. Although our sample sizes are small, with minimal replication, we discuss our results in the context of reduced pairing success and male-biased sex ratios in small, isolated populations. In addition to documenting singing activity patterns to optimize future surveys for species of conservation concern, ARUs may also signal potential demographic differences important for population persistence that warrant further exploration.

The annual patterns of precipitation in the dry deciduous forest of Madagascar are characterized by a dry season when the majority of trees lose their leaves and a wet season with full foliage development. Such variation allows the examination in shifts in the vertical distribution of birds and to their response to changing environmental conditions. Patterns of birds in the dry deciduous forest of Kirindy CNFEREF, central western Madagascar, were analyzed related to the vertical variation of vegetation structure and microclimate during 2 study periods: the dry (24 Aug to 16 Sep 2017) and wet seasons (25 Jan to 17 Feb 2018). Six line transects in forest habitat of 1,000 m each were used to survey birds, and each was associated with linear sampling to quantify vegetation structure. Data loggers were employed to record temperature and relative humidity across the vertical strata. During the dry season, associated with the microclimate aridity and reduction in vegetation cover in the upper strata, the number of species and individual birds found on the ground increased. During the wet season, fewer birds occurred on the ground, and abundance and species richness increased in the canopy. These results show the sensitivity of birds with regard to environmental fluctuations. However, regardless of the season, birds frequented mainly the mid-story, which had the highest abundance of species as compared to upper and lower vertical strata.

Breeding biology data are crucial for avian life history theory, but this information is unavailable for nearly half of the current living tropical bird species. Predation is the main driver of nest survival among tropical birds, and spatial and temporal factors may affect nest predation risk and survival. In this study, we describe the breeding biology of the Rusty-backed Antwren (Formicivora rufa), a bird that inhabits a coastal sandy plain in southeastern Brazil, and examine the effects of date and microhabitat features on nest survival. We found 47 nests over 2 breeding seasons. The nesting season lasted 7–8 months. The mean (± SD) nest-building time was 7.3 ± 1.1 d, the mean incubation period was 16 ± 1.9 d, and nestlings remained in the nest for 10 ± 0.8 d for a full nesting cycle that lasted for ∼26 d. Clutches invariably had 2 eggs and egg-laying occurred over 2 consecutive days. Males and females were both observed building nests, incubating eggs, and feeding nestlings and fledglings. We also report a nestling with a depigmented body, which may represent albinism. Most nests were depredated (68.1%, n = 32). Nest survival was constant throughout the breeding seasons and did not vary with microhabitat features (nest height above the ground, and vertical and horizontal distances between nest and shrub edges). The nesting biology of the Rusty-backed Antwren fits the general pattern typical of antbirds, and micro-spatial or temporal features cannot predict nest survival in our study population.

The Yellow-headed Parrot (Amazona oratrix) is considered globally endangered due to intense poaching pressure and extensive tropical forest loss. We examined the relationships among nesting pair density, survey area, tropical forest type, and forest conservation conditions to estimate the potential population size in central-western Mexico. The surveyed areas constitute a representative sample of forest types, property ownership, and land use in the region. We estimated the overall surveyed area and the nesting pairs in general and by each forest type. Data were analyzed in multiple and single linear regression models. We used a high-resolution vegetation model to measure the extent of each forest type and land use in the area with suitable climatic conditions for nesting. We recorded 111 nesting events in 77 distinct nest trees during the 2002–2013 study period in an area of 185.3 km². Overall nesting density was 0.59 ± 0.28 pairs per km². Individual areas surveyed showed a broad variation in nest densities (0.14–1.5 per km²). Primary tropical semi-deciduous forest held 64% of the nesting pairs and the highest nesting density (1.98 ± 0.82 per km²). Tropical dry deciduous forest contained 11% of nesting pairs and 0.20 ± 0.19 pairs per km². Single linear regression models by forest type performed better and are more practical for abundance calculations than multiple regression models. We estimate the size of the nesting population in the region at 701 pairs (95% CI: 526–876), which corresponds to about 1,399–2,330 parrots, using the mature/immature ratio used by the IUCN. The results suggest that central-western Mexico may hold about 27% of the species' global population.

Belted Kingfishers (Megaceryle alcyon) are widely distributed across aquatic environments in North America, but their behavior in marine habitats remains understudied, especially during the post-fledging period. We recorded daily activity budgets of adult and fledgling Belted Kingfishers on San Juan Island, Washington, and investigated the effects of tides and age class on feeding behaviors. Feeding attempt rate was highest at high tide, but strike success was highest at low tide. Adults foraged more successfully than juveniles and caught fish almost twice as large, consistent with juvenile inexperience during the post-fledging period. Strike success rates also varied between study sites for both adults and juveniles, potentially reflecting habitat quality. These results improve our understanding of how Belted Kingfishers behave in marine environments, and to our knowledge provide the first study of marine Belted Kingfishers during the post-fledging period. Follow-up studies quantifying prey availability and comparing seasonal behaviors of kingfishers in freshwater and marine habitats may help clarify the mechanisms behind the patterns we observed.

Knowledge of the breeding behavior of Evening Grosbeaks (Coccothraustes vespertinus) is based largely on a multiyear study in Colorado during the 1980s. In Colorado, the duration of full incubation bouts by female grosbeaks had a mean of 26.6 min, a value repeated since then in the literature. For one nesting pair of grosbeaks I studied in Montana, full incubation bouts (n = 5) by the undisturbed female during 22 h of direct nest watches on 7 d in June 2018 had a mean of 112.6 min (range = 45–202 min), much longer than the value reported in the Colorado study. Incomplete incubation bouts (female already incubating on my arrival or at my departure) by the undisturbed Montana female (n = 11) during the same observation period had a mean of 56.2 min, 4 of which were a minimum of 94–146 min, further suggesting that longer duration incubation bouts may be the norm for this species. Duration of incubation bouts for Evening Grosbeak in the Colorado study appear to be brief relative to other North American fringillids, but my limited data suggest that Evening Grosbeaks are typical in this regard. Mean duration of 10 nest absences by the undisturbed Montana incubating female was 9.7 ± 7.6 min (range = 3–26 min), similar to the Colorado study (10.1 ± 10.7 min). Male behavior during incubation also appeared similar to results from Colorado (no attending the eggs, frequent exchange of vocalizations with the nesting female, escorting and feeding the female only when off the nest). I conclude that the duration of nest watches (60–80 min) in the Colorado study was inadequate to determine the length of many longer incubation bouts by female Evening Grosbeaks.

In the breeding season f 2018, we found a much larger egg in one nest of Cinereous Tit (Parus cinereus) in Zuojia Nature Reserve, Jilin Province, China. The tit pair abandoned their nest soon after the alien egg hatched, which resulted in the death of the foreign chick. Based on DNA identification, this foreign chick was confirmed as a Great Spotted Woodpecker (Dendrocopos major), suggesting that the woodpecker laid or carried one of her own eggs into the tit nest. Limited cavity availability as the woodpecker lost its own nest might have contributed to this occurrence.

Saltmarsh Sparrows (Ammospiza caudacuta) are highly specialized tidal marsh obligates that are predicted to go extinct within this century as inundation of nests becomes increasingly frequent due to sea level rise. Short-term strategies for boosting reproductive success are greatly needed while best management practices for habitat restoration are being developed. Fostering orphaned chicks in active nests may be one such strategy. Males provide no parental care, so the loss of a nesting female will doom the brood. We confirmed the predation of a female attending a nest that contained two 6-day-old chicks. We translocated these 2 nestlings into an active Saltmarsh Sparrow nest at the site with similar-aged chicks. All chicks reached fledging age and were gone from the nest soon thereafter. This is the first documented case of a nestling translocation of a Saltmarsh Sparrow being performed, and it appeared to be successful, although survival of the fledglings throughout the subsequent year remains to be documented. Based on our result, translocation bears further experimentation and modeling to determine the probability of success and potential contribution to population trends.

Little is known about the migration of the Gray-headed Lapwing (Vanellus cinereus). During the fall migration season of 2018, we tracked 3 birds from Guiyang Airport, China, a stopover site of Gray-headed Lapwing, in order to analyze their migratory and wintering movements by means of GPS-GSM satellite telemetry. We obtained 3 partial fall migration routes and 2 complete spring migration routes from September 2018 to July 2019. We identified E India and Bangladesh as their wintering ground and NE and E China as their breeding area. The spring migration covered 3,380 km and took 12 d on average (n = 2). Gray-headed Lapwings migrated at night, flying at speeds of 29.11–91.12 km/h. In winter, the mean home range area (95% utilization distribution) was 18.56 km² (SD = 21.74, 3 birds) and the mean core area (50% utilization distribution) was 1.28 km² (SD = 1.49, 3 birds).

This study reports on findings about the natural history of the Cloud-forest Pygmy-Owl (Glaucidium nubicola). Recently described as a species, the general ecology of the Cloud-forest Pygmy-Owl remains poorly documented. Three banded individuals at a private reserve in the province of Pichincha, Ecuador, are used to describe its habitat use, diet items, and individual longevity. Our observations suggest this local population prefers wet primary cloud forest and appears to have a generalist diet. Multiple recaptures of a banded individual indicate a longevity record of 5 years. Additionally, ectoparasites were found on 2 out of 3 captured individuals.

Parent birds often vocalize near the nest to communicate with each other and their young. We observed a call made by Black Phoebes (Sayornis nigricans) as they approach the nest to feed their young that has not previously been studied in this context. The Wee call is more complex than the simple call that males and females commonly make near the nest. We hypothesized that one parent makes the call when arriving at the nest with food to signal to a brooding parent to depart from the nest. Over 3 years, we collected observational data at phoebe nests by observing them once during the incubation stage and then early and late in the nestling stage. As we predicted, phoebes did not make the Wee call during the incubation stage. When individuals approached the nest with food and made the Wee call during the nestling stage, the brooding parent normally responded by leaving the nest. Additionally, the brooding bird was likely to return to the nest if the other parent made the Wee call upon departing. While vocalizations near the nest can attract predators, in phoebes these calls appear to coordinate parental care efforts.

We investigated both social and foraging plasticity in a population of Common Loons (Gavia immer) that overwinter inland on Lake Jocassee Reservoir, South Carolina, using transects and time-activity budgets from 4 January to 10 March 2017. Loons were observed as either solitary individuals (65%) or in groups (35%, i.e., within ≤5 body lengths of another loon). Loons were more social (i.e., in groups) on transects with a river mouth (40.9% ± 7.1) than on transects without a river mouth (24.2% ± 5.4). The mean (± SE) dive duration for solitary loons was 71.3 ± 7.7 s (n = 46, range 15–219 s) and several dives exceeded 2 min (22.2%, 10/46). In contrast, 15 foraging flocks were characterized by numerous shallow dives of <20 s. The mean group size (± SE) was 6.9 ± 0.8 individuals and group foraging bouts lasted 8.3 ± 1.2 min. In addition, Horned Grebes (Podiceps auritus) and Ring-billed Gulls (Larus delawarensis) joined loons forming multispecies foraging flocks, 26.7% and 13.3% of the time, respectively. These data indicate Common Loons wintering at Lake Jocassee are social and exhibit foraging plasticity.

We documented a potential interspecies feeding event between 2 species of hummingbirds in southeastern Mexico in 2019. We used morphological and behavioral traits to identify the hummingbirds as an adult female White-bellied Emerald (Chlorestes candida) and a juvenile Rufous-tailed Hummingbird (Amazilia tzacatl). We ruled out the possibility of hybridization due to a lack of intermediate traits in the juvenile hummingbird, which allowed for the speculation of 4 interspecies behavioral mechanisms: brood parasitism, courtship feeding, simultaneous multiple nesting, or alloparental care of young. Due to the complexity of the first 3 mechanisms and lack of documented evidence of the behaviors between the 2 species of hummingbirds, the most likely mechanism to explain the observed behavior is alloparental care of young by an inexperienced adult female White-bellied Emerald.

Cattle Egrets (Bubulcus ibis) are active foragers that typically pursue and capture insects flushed by grazing mammals. Arboreal foraging by Cattle Egrets has occasionally been reported, although this behavior appears to be rare, poorly documented, and not well understood. We observed Cattle Egrets arboreally foraging at 2 locations in Myanmar: Yangon University (24 Dec 2018–7 Jan 2019) and Khamti (1 Apr 2019). We observed Cattle Egrets at Yangon University feeding in the canopy of a mango tree (Mangifera indica) on swarms of pollinating insects attracted to flowers. Foraging egrets were scattered throughout the canopy; most remained stationary beside a single flower cluster to catch insects, although on occasion more active behaviors were employed. In Khamti, we observed Cattle Egrets perched on trees above an emergence of winged termite alates (Isoptera). Egrets remained stationary and attempted to capture flying termites in close proximity. Our observations together with other published reports suggest arboreal foraging by Cattle Egrets may occur under the following conditions: (1) when insects are concentrated in trees (e.g., pollinators swarming at flowers) and/or (2) when an elevated perch provides access to flying insects. Our observations at Khamti appear to be the second record of Cattle Egrets among bird assemblages opportunistically preying on alate termites.

We report the first record of Bronzed Cowbird (Molothrus aeneus) brood parasitism on the year-round resident Golden-crowned Warbler (Basileuterus culicivorus). Our observations represent the 105th known host species for this cowbird species and the ninth known host species from the Family Parulidae. Our assignment of these records to the true host list are based on observations of a pair of Golden-crowned Warblers feeding caterpillars to a Bronzed Cowbird fledgling in a shade coffee plantation in Zentla, Veracruz, Mexico.

The European Starling (Sturnus vulgaris) is a cavity-nesting species that aggressively competes with other cavity nesters, such as woodpeckers, and usurps their nest cavities. Interspecific parental care among birds is uncommon and scarcely reported for European Starlings and woodpeckers. Here, we report an observation of a clutch of 3 Hairy Woodpecker (Dryobates villosus) nestlings being fed by both an adult female Hairy Woodpecker and at least 1 adult European Starling in southern Ontario, Canada. There are differences in parental behavior observed between the starling and female Hairy Woodpecker, namely only the starling entered the cavity (7.0 times/h) and removed fecal sacs (4.2 times/h) while the female Hairy Woodpecker never showed these behaviors during our observation period, but she fed nestlings 7.4 times/h compared to 4.9 times/h by the starling. Although proximate causes of this behavior are unclear, nest site competition, overlap of the timing of breeding and preferred habitat, or the loss of the male woodpecker may have triggered this behavior.

Filial cannibalism (cannibalistic infanticide) is a common strategy among raptors though rare among other groups of birds. We describe the first case of possible parental infanticide followed by cannibalism by an adult and nestmates of Red-legged Seriema (Cariama cristata) in a brood of 3 in the Cerrado (savanna-like) ecosystem. A 20 min video recording showed a possible parent killing and eviscerating 1 of its nestlings and subsequently feeding it to the other 2 nestmates. This new record of brood reduction for wild Cariamidae might be a common behavior in both species of the family and may increase food availability and survival of the larger nestlings.

Climate change has advanced the onset of spring and, subsequently, avian nesting activity. Although this advance can have negative consequences such as phenological mismatch, species may be able to increase the annual number of young fledged. Eastern Bluebirds (Sialia sialis) can rear 3 broods to fledging, but in this paper we report 3 pairs that reared 4 broods to apparent fledging in 2016 and 2020 in northeastern Arkansas. Nesting attempts began as early as 18 March with the first laid egg and concluded as late as 18 September with the last fledging event; brood sizes ranged from 2 to 5 chicks. Nests were checked daily 15–18 d post-hatching, increasing confidence in our determination of successful fledging. Unlike a previous report of 4 broods reared by a male that mated with 2 females at once, the pairs at our site all remained together through all 4 attempts. These pairs all consisted of after-second-year birds and we discuss why we believe these nests were successful, as well as factors that allowed these pairs to attempt to rear an additional brood.

Birdsong's primary function is attracting and stimulating mates and repelling rivals during the breeding season. However, many species also sing during the nonbreeding season, which raises questions about the function of nonbreeding season song and the mechanisms underlying its production. In this study, we compared spectral and temporal measurements from a large sample of breeding (N=267) and nonbreeding season songs (N=283) of the Carolina Wren (Thryothorus ludovicianus), a nonmigratory, temperate species that sings year round. We found that breeding season songs were longer than nonbreeding season songs and had more syllables within each song. Trill rate, the number of notes per syllable, minimum and maximum frequency, and frequency bandwidth did not differ detectably between the 2 seasons. This study is the first to examine seasonal song differences in Carolina Wrens and provides a basis for future investigations into the drivers behind this seasonal variation.