The Ferruginous Hawk (Buteo regalis) is a keystone raptor in arid-land ecosystems in western North America that is experiencing population declines in some regions. Range-wide migration patterns, destinations, and chronology of adult hawks have not been described. Between 1999 and 2014, we captured 69 adult Ferruginous Hawks east and west of the Continental Divide and monitored them ≤6 yr with satellite telemetry to document their migration ecology. During a short time (x̄ = 30 d, SD = 23) before migrating, 22% of hawks made brief movements away from territories (x̄ = 211 km, SD = 133) and then returned. Migrating hawks (98% of 89 analyzed patterns) moved across broad fronts using five different strategies in three distinct periods: summer (July–August), fall (September–November), and spring (February–March). Breeding range longitude and latitude strongly influenced (r = 0.78) timing of summer migration that was directed to focal areas shared by breeding populations of hawks in the Northern Grasslands and Central Plains. Hawks nesting in grasslands from Canada to the Southern Plains demonstrated a strong pattern of southward migration to summer and winter ranges along the east front of the Rocky Mountains to central Mexico. Hawks from shrub-steppes in the Columbia Basin and Great Basin migrated eastward to summer ranges across the Continental Divide to grasslands, then to wintering areas in California and northern Mexico. On average, adult hawks spent 64% of the year away from breeding home ranges and migrated 2376 km (SD = 1165) annually, but differences in migration destinations, distance (P = 0.048), and duration (P < 0.0001) among populations potentially exposed them to variable levels and types of stressors. Accordingly, conservation of nonbreeding habitats used by Ferruginous Hawks is important for maintaining health of breeding populations; conservation efforts should emphasize protection of fossorial prey and habitats on shared summer ranges and winter ranges in the Mexican grasslands and Central Valley of California.

Collisions between wildlife and aircraft (wildlife strikes) pose notable risks. Previous research has found that a variety of birds and mammals are involved in wildlife strikes, but no comprehensive evaluation of collisions between owl and aircraft (owl strikes) has been conducted. We queried the Federal Aviation Administration's National Wildlife Strike Database (from 1 January 1990 to 30 June 2014) and the US Air Force's Birdstrike Database (from 1 January 1994 to 30 June 2014) to characterize owl strikes. We found 2531 owl strikes involving at least 20 species of owls. Barn Owls (Tyto alba) were the most frequently struck species, accounting for 42% of all reported owl strikes. Almost 75% of owl strikes occurred during the night. Owl strikes typically occurred within the airfield environment itself, and 86% of owl strikes occurred when the aircraft was at or below 30 m above ground level. Some mitigation tools and techniques (e.g., nonlethal hazing, translocation, lethal removal) can reduce the frequency of owl strikes, but the efficacy of these methods remains unevaluated. An important area of future research will involve the development and evaluation of effective, publicly acceptable methods of reducing human–owl conflicts.

Although best known for capturing live prey, five of the six members of the genus Falco in the United States or Canada are documented facultative scavengers. During 1109 surveys of three coastal beaches in Washington between 1983 and 2015, we observed hunting and feeding by Peregrine Falcons (Falco peregrinus), a species that migrates through and overwinters at those coastal beaches. Excluding records of Peregrine Falcons with food items of unknown origin (n = 44), our 172 observations of feeding included 77 prey items that we concluded the falcons had captured, 46 direct observations of prey captures, and 49 cases of scavenging. Scavenging records represented 29% of our observations of Peregrine Falcons with food items, and included food items representing 19 taxa. Seabirds and waterbirds were the most common food items consumed as carrion (44 of 49 items; 90%), whereas other captured or targeted prey were most often shorebirds or other small birds (206 of 277 items; 74%). We observed 21 color-banded falcons, ranging in age from <1 to 4 yr, scavenging up to three times each. We observed more scavenging by immature (<1 yr old) falcons than by adults, even though hunting success was similar between immature and adult falcons. We detected no difference in the occurrence of scavenging by season. Given the frequency of scavenging, the biomass of carrion potentially consumed, and the apparently predictable presence of carrion in the study area, we concluded that scavenging by peregrines in coastal Washington is relatively common. Additionally, carrion may represent a commonly used and important source of food in other regions of the world, particularly where carrion is common and persistent in the environment.

We conducted surveys of breeding pairs of the endemic and globally “Near Threatened” Striated Caracara (Phalcoboenus australis) on 79 outer islands in the Falklands archipelago (Islas Malvinas) during the austral-summer breeding seasons of 2013–2014 and 2014–2015. A total of 354 breeding pairs (defined as pairs with evidence of egg-laying), or an archipelago-wide adult breeding population of at least 0.05 birds/km² was recorded. An additional 477 probable breeding pairs also were found. The distribution of breeding pairs remains similar to that found during surveys in the 1990s and 2000s. Grand Jason, Steeple Jason, New Island, Beauchêne Island, and Bird Island, the five islands with the highest numbers of breeding pairs, accounted for half of the total breeding population. “Vegetationally pristine” islands with dense areas of tussac grass (Poa flabellata) and high densities of small burrowing seabirds—namely Bird Island, Saddle Island, and Beauchêne Island—supported the highest densities of breeding pairs. Eighty percent of all pairs occurred on National Nature Reserves or on privately owned nature sanctuaries. Our surveys suggest that sustained protection of key breeding sites is critical for the long-term conservation of this species. We recommend that populations of Striated Caracaras at Tierra del Fuego also be surveyed and that the global population status of the species be reassessed.

Sexual differences in parental care investment may affect individual survival or performance, and also demography. We investigated parental-care behavior of the endangered Chaco Eagle (Buteogallus coronatus) to evaluate implications for population conservation in semiarid habitats of central Argentina. From 2004 to 2012, we monitored three breeding attempts using video recording (275 hr) during the incubation period, and nine pairs during the nestling-rearing period by means of video recording (1087 hr) and focal observations at nests (232 hr). Chaco Eagles showed a strong division of parental care by sex. Females contributed significantly more than males to incubation, shading/brooding, and feeding of the nestling, whereas males provided prey to females during incubation and to nestlings during the early nestling-rearing period. Foraging males, which spend more time away from the nest, may be more exposed to anthropogenic activities and negative interactions with humans. If males are more vulnerable to such effects, this could decrease the survival of breeding males and potentially increase the recruitment of immature males to the breeding population. In this event, the ability of the inexperienced immature males that replace the adult eagles to cope with the food and care demands of the mate and offspring is critical for ensuring Chaco Eagle population maintenance.

The Black Kite (Milvus migrans) has a limited distribution within Taiwan due to a dramatic population decrease during the late 20^th century. Prompted by some poisoning incidents of Black Kites and other farmland birds, we hypothesized that poisoning may be an underreported yet important threat. Thus, we created a citizen-science Facebook group in October 2014 in order to receive more information about possible poisoning incidents. By September 2016, we had received reports of 4753 dead birds in 213 separate poisoning incidents in agricultural areas. The types of fields most often associated with poisoning incidents were direct-seeded rice (Oryza sativa), rice that was soon to be harvested, and red beans (Vigna angularis). We tested tissues from 29 dead small birds for pesticide residues. Twenty-eight birds contained carbofuran, and one bird contained terbufos, both highly toxic pesticides. Furthermore, of seven dead Black Kites tested from 2010 to 2016, four contained carbofuran, and three contained second-generation anticoagulant rodenticides. After interviewing farmers and reviewing older agricultural literature, we concluded that most of these incidents represented intentional poisonings by farmers attempting to control avian pests and rats (mostly Bandicota indica and Rattus spp.). We suggest that the Black Kites were likely the victims of inadvertent secondary poisoning incidents. The dramatic decrease of the Black Kite in the 1980s coincided with the rapid increase in the area planted with direct-seeded rice and the widespread use of carbofuran and rodenticides. The recent decreased use of these pesticides due to restrictions has coincided with the recent slow recovery of the Black Kite population. Therefore we initiated public awareness campaigns, and the Taiwanese government has adjusted some pesticide-use policies.

The Forest Owlet (Heteroglaux blewitti), Spotted Owlet (Athene brama) and Jungle Owlet (Glaucidium radiatum) are small owls coexisting in the East Kalibhit Forests in the Khandwa District of Madhya Pradesh State, India. We compared their diets to better understand their food habits, dietary overlap, and the mechanism of their coexistence. The diet of the three species differed significantly. The diet of the Forest Owlet was dominated by small mammals (52.2%, by frequency), whereas invertebrates dominated the diets of the Spotted Owlet (58.1%) and Jungle Owlet (84.8%). The Forest Owlet consumed a wider array of prey (food-niche breadth [FNB] = 0.40) compared to the Spotted Owlet (FNB = 0.13) and the Jungle Owlet (FNB = 0.06). The dietary overlap was highest between the Forest Owlet and Spotted Owlet (56%), lower between the Spotted and Jungle Owlet (28%), and lowest between the Forest and Jungle Owlet (22%). Diets also differed significantly among the three owls in terms of the mean prey mass of the species consumed. The Forest Owlet is a generalist predator feeding on various sizes and types of prey; the Spotted Owlet feeds on large and medium-sized mammals, as well as invertebrates, and the Jungle Owlet is a specialist feeding mainly on invertebrates and small mammals. Our results suggest the three species coexist by consuming prey of different sizes.

Elucidating the differential use of resources by animals is fundamental to both understanding ecological processes and making informed conservation decisions. Such information is particularly important for poorly studied species that may be dependent upon heavily exploited resources. We examine habitat selection of the Northern Pygmy-Owl (Glaucidium gnoma), which is thought to depend upon mature forests, but for which information on habitat use is scant. We conducted our study in northern Idaho and western Montana, and used the synoptic model of space use. We obtained sufficient location data to include 27 radio-tagged owls in the study (16 in Idaho and 11 in Montana). To evaluate habitat selection, we developed 36 models in Idaho and 24 models in Montana, each with different combinations of habitat covariates hypothesized to influence Northern Pygmy-Owl space use. Covariates representing larger tree size were statistically significant ( ≥ 3.01, t ≥ 2.7, P ≤ 0.02) predictors of space use in the best-supported population-level models in both Idaho and Montana. In addition, the distance-to-stream covariate was a statistically significant ( = −3.60, t = −3.3, P = 0.005) predictor of the probability of use in the best-supported population-level model in Idaho, but not in the best-supported Montana model ( = −0.08, t =0.03, P = 0.98). Owls selected forested areas with larger tree sizes and (in Idaho) selected areas closer to stream courses. Differences between the two study areas in the apparent importance of stream proximity to habitat selection may reflect differences in timber harvest practices and the amount of coniferous vegetation; however, this hypothesis should be addressed with additional research.

Evaluating raptor populations is challenging because of their low population densities and secretive breeding behavior. Barn Owls (Tyto alba) are particularly difficult to monitor given their nocturnal nature and irregular vocalization patterns. In an effort to help develop more effective survey protocols for locating breeding Barn Owls and for monitoring Barn Owl populations, we examined factors influencing Barn Owl detections and responses to broadcast surveys. We conducted 288 surveys at 33 different nest locations in 2013 and 2014 in Illinois, USA, and examined the influence of using call broadcasts, breeding stage, day of year, cloud cover, moon phase, time of night, wind speed, ambient noise, temperature, and the number of Barn Owls in proximity on detection rates. We detected Barn Owls on 11.2% of passive surveys and 49.4% of broadcast surveys; 97.6% of the detections during broadcast surveys involved individuals flying within 20 m of observers. Detections were more common earlier in the breeding season and in areas where density of known Barn Owl nests was greater, but these variables affected detections from broadcast and passive surveys similarly; other variables did not have meaningful associations with Barn Owl detections. These results suggest that broadcast surveys may be an effective approach for identifying areas where Barn Owls are breeding or for monitoring population trends.

Roost sites are likely an important component of the American Kestrel's (Falco sparverius), kestrel(s) hereafter, nonbreeding habitat, as quality roost structures can provide thermal cover and protection from predators. We studied winter roost-site use by kestrels in an agricultural landscape in South Texas, where the population is composed of a combination of territorial wintering birds and migrating individuals passing through. Through observations of color-marked and unmarked birds, we identified 50 roost sites during September–March, 2014–2017. Kestrels utilized foliated shrubs and trees as roosting sites (n = 24), as well as various human-made structures (n = 26) including buildings, petroleum and farm equipment, and electrical structures for roost sites. Roost sites varied greatly in the level of concealment and exposure, with seven kestrels roosting on electric structures that allowed high levels of exposure to weather and potential avian predators. We observed aggression between kestrels around roost sites, and we documented small communal kestrel roosts. Because we observed roosting in sites exposed to weather and predators, aggression around roost sites, and communal roosting, we speculate that roosting sites suitable for kestrels may be limited or poorly dispersed in this agricultural landscape.

Raptor rehabilitation programs allow thousands of raptors to be released back into the wild each year that otherwise would have perished without medical treatment. Although species-specific and age-specific results from research conducted across the nation vary greatly, there is a general consensus that raptor rehabilitation is an important part of raptor conservation. We investigated differences in diagnoses and treatment outcomes, along with survival and release rates for 1225 individuals of 17 species admitted between 2010 and 2014 to the Southeastern Raptor Center (SRC), a raptor rehabilitation center in the southeastern United States, to identify trends related to age, species, and activity type (diurnal vs. nocturnal). Adult nocturnal raptors were admitted more frequently than young birds, but we found the opposite trend for diurnal raptors. Young diurnal raptors had higher release rates than adults, likely due to their less-severe injuries. Nocturnal species were more often involved in vehicle collisions than diurnal raptors and were admitted most commonly for head trauma. Diurnal birds were more frequently shot than nocturnal raptors, but were treated most often for fractures, body trauma, and other injuries and illnesses. The SRC had an overall raptor release rate of 38%, which is higher than that of many other rehabilitation centers, and a survival rate of 42%. These results, based on a large number of individuals and a wide diversity of raptor species, may be helpful for informing and improving raptor rehabilitation efforts in the region.

We report on the nesting of Southeastern American Kestrels (Falco sparverius paulus) in nonnative Monk Parakeet (Myiopsitta monachus) nests in Florida, USA. Two kestrel pairs nested within parakeet stick nests located on top of steel support structures at electric utility substations in Pasco County, Florida. Kestrels fledged young at both sites. The Monk Parakeet's ability to exploit anthropogenic habitats may facilitate the use of these areas by nest-site-limited species such as the Southeastern American Kestrel.

During a nest-camera study of Hen Harriers (Circus cyaneus), we recorded siblicide, cannibalism, movement of nestlings by adult birds, and interactions with predators. We deployed cameras at 13 nests across three study areas in Ireland between 2008 and 2010. At a nest with two well-developed nestlings (approximately 25–30 d old), the older nestling killed its sibling and fed on it. This was the first documented case of siblicide in this species, to our knowledge. Recordings also revealed three other events of cannibalism in which one of the nestlings in a brood died from unknown causes and was then eaten by its siblings (n = 1), by the adult male (n = 1), or was used by the adult female to feed the remaining nestlings (n = 1). At two nests, recordings showed the adult female picking up and moving nestlings that were outside the nest cup. In addition, cameras recorded two instances of full brood predation by red fox (Vulpes vulpes) and an attack on a nest by a female Eurasian Kestrel (Falco tinnunculus) that had no apparent consequences for the nestlings or the female Hen Harrier. The behaviors reported here, which are difficult to observe directly, may have important consequences for our understanding of productivity and population dynamics of Hen Harriers.