The Broad-winged Hawk (Buteo platypterus) is an obligate long-distance migrant that breeds in deciduous and mixed forests of North America and migrates to Neotropical regions to overwinter. Despite advances in understanding the breeding ecology and migration of this species, the overwintering period and associated threats remain understudied. We used telemetry data to quantify land cover composition and threats during the overwintering period of seven females affixed with Argos solar-powered transmitters between 2014 and 2018. Broad-winged Hawks in our study nested in Pennsylvania, USA, and overwintered in Colombia, Brazil, and Peru. Overwintering areas varied in size (x̄ = 243.6 ± 101.2 km²) and were composed of evergreen sub-montane forests, lowland non-flooded forests, and lowland flooded evergreen forest. In general, the loss of forest cover in all areas used by Broad-winged Hawks in our study did not exceed 10% of the total overwintering area used, suggesting Broad-winged Hawks may select wintering areas with little forest disturbance. Illegal mining was a common disturbance in areas used by Broad-winged Hawks overwintering in southern Peru, and forest fires were the prevalent disturbance in the overwintering area of Mato Grosso in western Brazil. These results provide the first analysis of land cover composition and threats of Broad-winged Hawks during the overwintering period. Although more data are needed to determine specific habitat selection for this species, our study suggests large forested areas in the Neotropics are key to ensure the conservation of the Broad-winged Hawk during the overwintering period, an understudied stage of its annual cycle.

South America is home to the highest diversity of birds on the planet, yet we still understand relatively little about their seasonal movements, or even which species are migratory. During two consecutive years, we used satellite transmitters to study the movement ecology of 10 individual Snail Kites (Rostrhamus sociabilis) captured in southern Brazil. We detected highly variable movement patterns among Snail Kites, with some migrating between two well-defined sites, migrating up to 4000 km to the mouth of the Amazon River. Others exhibited nomadic/facultative movements, moving different distances and to different sites between seasons and years. Overall, Snail Kites spent most of the migration period at stopover sites, moved at a higher speed, and used fewer stopovers in austral spring than in fall. These results provide the first evidence that Snail Kites in South America move across large distances, effectively connecting major watersheds, and suggest that individual Snail Kites are highly flexible in how they track resources over time and space. The complex movements and highly variable migratory behavior we detected among Snail Kites points to the need for more detailed research on the behavioral ecology and risks to survival across the annual cycle and broad range of this enigmatic and poorly understood species.

Reintroductions are an important tool in conservation for preserving and enhancing biodiversity and preventing extinction, and post-release monitoring is essential to evaluate and inform conservation management and maximize recovery success. By quantifying genetic diversity levels and effective population size (N_e) over time, managers can gauge to what degree additional efforts are needed to increase the likelihood of population persistence. The endangered Northern Aplomado Falcon (Falco femoralis septentrionalis) population in South Texas was reestablished and supplemented with captive-bred individuals originating from 27 founders collected in eastern Mexico (San Luis Potosí, Veracruz, Tabasco, and Chiapas). A total of 927 Aplomado Falcons were released at 23 locations along the southern coast of Texas between 1985 and 2004, and in 2012 and 2013. To assess the species' reintroduction and recovery, we applied a genetic monitoring approach using sampled nestlings (n = 267) from a total of 108 nests in 2004–2005 and 2012–2016. Based on ten microsatellite loci, levels of genetic diversity (i.e., allelic richness and heterozygosity) remained stable over the sampled time period, with no indication of inbreeding. Diversity levels were comparable to a subset of samples collected from the captive population founders (n = 11). Similarly, individuals from the South Texas population showed strong admixture with the founding population, and levels of both N_e and of effective breeding (N_b) showed no signs of decline over the sampled time period. To what degree overlapping generations and the release of additional Aplomado Falcons during the sampled time period limited our assessment of the South Texas population is not fully known. Continued monitoring across multiple generations is advisable to assess the population's ability to persist.

The Peregrine Falcon (Falco peregrinus) breeds locally in the Guerrero Negro wetland complex, Baja California Sur, Mexico, but the most recent investigation of their breeding ecology in this wetland area was in 1998. Our objectives were to update the information on the reproduction of Peregrine Falcons in Guerrero Negro and to evaluate the relationship of reproductive parameters with the environmental temperature, rainfall, and nest substrate (natural or artificial). From 2012 to 2016 we surveyed for Peregrine Falcon nests, and monitored them from February to May each year. We recorded the type of nest substrate (natural or artificial) and the nest contents (eggs, nestlings, or fledglings) at every visit. Pooled across years, we recorded 34 reproductive events that produced 42 fledglings. On average per year, there were 6.8 ± 1.6 egg-laying pairs, and 4.4 ± 1.8 were successful, with a productivity of 1.23 ± 0.06 fledglings/egg-laying pair. Monthly mean air temperatures and rainfall had no effect on breeding parameters; however, there were significant relationships with type of nest substrates. On average, we found falcons had greater nesting success and productivity on artificial substrates (83 ± 15% and 1.91 ± 0.12 fledglings/egg-laying pair) than on natural substrates (36 ± 21% and 0.36 ± 0.21 fledglings/egg-laying pair). Compared to the 1998 estimate, the number of egg-laying pairs in Guerrero Negro has more than doubled (from four to nine); this wetland area currently holds the largest number of breeding pairs along the Baja California Peninsula.

We searched for nests and studied aspects of the breeding biology of Southern Caracaras (Caracara plancus) in the Patagonian grasslands biome of southern Santa Cruz province, Patagonia, Argentina, at the southern limit of the species' continental distribution. In this open, mostly flat landscape where potential nest substrates are rare and isolated yet conspicuous, caracaras nested in native Magellan barberry shrubs (Berberis microphylla), exotic trees associated with ranch houses and other buildings, on coastal cliffs, and on human-made structures associated with petroleum and gas extraction plants. These extraction activities, which began only in the past three decades in this region have provided new nesting opportunities for this species. Nest characteristics, brood size, and productivity recorded in our study area were similar to what has been previously reported for the Southern Caracara nesting across its broad latitudinal range. In our study area, average productivity in both years combined (2010–2011) was 2.1 fledglings per successful pair (n = 27). The nesting season for this caracara population apparently extends from September through January, phenology that is similar to that reported for caracaras nesting at a similar latitude in Chile and for other raptor species in Santa Cruz province. However, the nesting season seems to be shorter than for caracara populations nesting at northern latitudes in Argentina. In this vast, open landscape, nest substrates provided by human-made structures may be an important determinant of the spatial distribution of Southern Caracara nests.

The availability of habitat determines patterns of habitat use and selection by raptors, and habitat loss in human-modified landscapes may influence habitat use by individual raptors. This is important for tropical forest-dependent species, which face an accelerated rate of habitat loss worldwide. I evaluated habitat use and selection by Collared Forest-Falcons (Micrastur semitorquatus) in the fragmented rainforest of the Los Tuxtlas Biosphere Reserve, state of Veracruz, Mexico. I conducted vantage point and transect observations combined with playbacks to survey Collared Forest-Falcons in March–June 2012 and 2013. I estimated habitat use and selection by forest falcons that inhabit low forest-cover and high forest-cover landscapes. In general, Collared Forest-Falcons selected primary forest and included higher proportions of this habitat within their territories and core areas. Even though the falcons avoided cattle pastures, individuals inhabiting low forest-cover landscapes included a higher proportion of this land cover within their territories, probably as a response to low forest availability in the landscape. Results from this study demonstrate that Collared Forest-Falcons preferentially selected primary rain forests but also used secondary forests in Los Tuxtlas Biosphere Reserve. Low forest-cover in the landscape may be influencing habitat use patterns of falcons, forcing them to use a higher amount of the suboptimal habitat, and increasing their risk of mortality with potential consequences for population dynamics.

The Crested Eagle (Morphnus guianensis) is the second largest Brazilian forest eagle. Crested Eagles are distributed from southeastern Mexico to southern Brazil, northern Argentina, and Paraguay; however, the species is one of the least-studied Neotropical raptors. Our objective was to determine diet and feeding strategies for Crested Eagles in the Brazilian Amazon. We recorded Crested Eagle diet at four nests from 2010–2012 through a combination of direct observations from the ground, remote photographs (camera-traps), and pellets and prey remains collected in and under the nests. We identified a total of 79 prey individuals, composed of 21 different prey species. We found that Crested Eagles fed mainly on medium-sized rodents, and medium-sized to large mammals. Prey were mainly nocturnal (70%), including mostly scansorial, cavity-dwelling marsupials and rodents. Fewer prey were diurnal (20%) and these were typified by arboreal, gregarious mammals (monkeys); rare prey included one owl (Strigidae) and one porcupine (Coendou sp.). We suggest that this may indicate a diet not specialized on a particular prey species or group, but rather focused on specific prey behaviors or microhabitats.

Organic waste in garbage dumps serves as an easily obtained food subsidy for many species globally, with a variety of both positive and negative effects on animals' reproductive and health parameters. However, in some regions, such as southern Patagonia, this phenomenon remains unstudied. In Ushuaia, Tierra del Fuego province, Argentina, seven species of facultative and obligate scavenging raptors have been recorded using the garbage dump. During November 2018 to September 2019, we assessed seasonal garbage dump use by facultative and obligate scavenging raptors in Ushuaia, Argentina, and recorded abundance, mortality events, and microplastic ingestion. We observed up to 225 raptors of five species foraging in the deposit zone of the garbage dump, with a fourfold overall increase in early winter compared to the other seasons. We recorded 17 dead raptors of three species, and we identified shooting, entanglement, plastic ingestion, and electrocution as the causes of mortality. Even in samples collected from control birds not associated with the garbage dump, 80–90% of the excreta samples contained microplastics. We suggest that raptors at the Ushuaia garbage dump may serve as sentinel species for environmental monitoring programs, which can facilitate evidence-based conservation management.

Tropical owls are one of the most threatened groups of birds. Studying the association between landscape features and owl assemblages is challenging due to the logistical difficulties of nocturnal fieldwork. We analyzed the association of landscape composition and spatial configuration of forest cover with the composition of the owl assemblages in a tropical rainforest in southeastern Mexico. During the 2014 reproductive season (April to June), we estimated owl abundance through auditory detection and playbacks at 60 survey points distributed in 12 landscapes (625 ha each) within a gradient of forest cover. We found that the owl community comprised six out of the 10 expected resident species. The landscape unit with 41% forest cover contained the most diverse assemblage. The owl species most susceptible to local extinction were specialists of interior areas of old-growth forest. The abundances of the Middle American Screech-Owl (Megascops guatemalae), Great Horned Owl (Bubo virginianus), and Black-and-white Owl (Ciccaba nigrolineata) were positively associated with the proportion of forest cover as well as with the average size of the patches, but negatively associated with environmental temperature. The abundances of the Barn Owl (Tyto alba) and Ferruginous Pygmy-Owl (Glaucidium brasilianum) were positively related to the amount of urban area in the landscape. The only species recorded along the entire gradient was the Mottled Owl (Ciccaba virgata), a species that is a generalist in habitat and diet; its abundance was positively related to the proportion of forest cover and the amount of water surface (lakes and rivers) in the landscape. Four resident species were not recorded: Crested Owl (Lophostrix cristata), Spectacled Owl (Pulsatrix perspicillata), Striped Owl (Pseudoscops clamator), and Central American Pygmy-Owl (Glaucidium griseiceps).

Western Burrowing Owls (Athene cunicularia hypugaea; hereafter, Burrowing Owls) were once widespread residents of grasslands throughout western North America, but their range has contracted, and abundance has declined in some regions. The causes of declines and geographic variation in population trends of Burrowing Owls are unclear but may be linked to changing land use and urbanization. Burrowing Owls are often found in association with airfields and airports, and their presence at such facilities is sometimes considered to be in conflict with those operations. Documenting the long-term persistence of Burrowing Owls at active airfields can help airfield managers who face decisions regarding compatibility of owls and airfield operations. We report the results of a long-term effort to monitor Burrowing Owls on Kirtland Air Force Base in New Mexico, USA, including the rapid recovery of Burrowing Owl numbers from near-extirpation and the relationships between abundance and other demographic traits. The number of breeding pairs of Burrowing Owls increased from one pair in 2013 to 28 pairs in 2019 and 2020, and the number of fledglings produced increased from one in 2013 to 84 in 2019 and 61 in 2020. The recovery was not uniform across all areas of Kirtland Air Force Base, and some formerly occupied areas remained unoccupied. We documented dispersal outside the Air Force base boundary and that the number of breeding pairs was more strongly influenced by the number of offspring produced in the prior year than the number of owls returning from prior years, which indicated that the population is part of a larger meta-population. Our results demonstrate that the maintenance of Burrowing Owl populations is not necessarily at odds with safe airfield operations, that Burrowing Owls exhibit complex population dynamics, and can rapidly recolonize previously occupied areas if habitat and nest sites remain suitable.

Nesting in burrows is uncommon among birds, but one example of a burrow-nesting raptor is the Burrowing Owl (Athene cunicularia). In most areas of North America, where this raptor has been extensively studied, it typically uses burrows of fossorial mammals, but in southern South America this owl digs its own burrows. We studied characteristics of size, lining, and decoration of Burrowing Owl nests located in dunes, rural areas, and urban areas of the Pampas of Argentina, and analyzed whether such characteristics vary according to land cover. We found that Burrowing Owls construct burrows of similar characteristics in the three habitats sampled, although nests in dunes had wider entrances and longer tunnels. Such variation might relate to the soil, which is more compacted in the dunes than at the rural and urban areas. In both rural and urban areas, owls used manure to line the burrow and decorated the nest entrance with visible objects, but the diversity and amount of materials used for decoration was much higher in urban nests. Our results on burrow measurements, burrow-lining, and decoration behavior of Burrowing Owls in the Pampas were consistent with those reported for North American populations, even though burrow construction processes differ at both ranges of the species' distribution.

The persistence of a species throughout its geographic range requires dispersal among its populations. The study of dispersal is particularly relevant for species whose geographic range has contracted, such as the endangered Northern Aplomado Falcon (Falco femoralis septentrionalis). We used Argos 5-g PTT-100 satellite transmitters to determine the movements of two wild Chihuahuan Desert Aplomado Falcons (one female and one male) from fledging to breeding (male), or transmitter failure (female), at 1062 d and 439 d of age, respectively. Both falcons dispersed from their natal territories 2–3 mo after fledging. These falcons then wandered between activity centers near historic breeding territories and some territories recently converted to farmlands. These two falcons also explored areas outside known breeding areas via some long-distance movements to areas of potential breeding habitat being converted to farmland. In 2 yr, movements of the male covered 7412 km². This falcon nested unsuccessfully with an unbanded female in a vacant breeding territory 15 km from his natal site. His nesting attempt the following year yielded two fledglings. While a breeding bird, the male falcon had a home range of 200 km². For 17 mo, the female falcon wandered through an area of 12,136 km². The farthest distance she traveled from her nest site prior to transmitter failure was 154 km.

We used photo-documented citizen science data held in publicly accessible databases to better elucidate the diet of one of the smallest Neotropical Accipitridae, the Tiny Hawk (Accipiter superciliosus). Previous data are exclusively anecdotal, but a suggestion that this species is to some extent a specialized predator on hummingbirds (Trochilidae) is widely reported in the literature, despite being based on few observations. Using a total of more than 680 photographs of Tiny Hawks, we identified 33 items of avian prey from 15 families and at least 25 genera, including one hummingbird and some comparatively large non-passerines. Prey also included one bat. Although the Tiny Hawk is perhaps more liable to predate hummingbirds than most other Neotropical raptors, the available data suggest that the Tiny Hawk, like many other Accipiter species, is primarily a bird specialist. As evidenced by other recently published studies, internet-sourced photographs might prove useful for similar dietary analyses for other poorly known raptors.