After a well-documented recovery following substantial population declines throughout most of North America, the Peregrine Falcon (Falco peregrinus) was delisted under provisions of the Endangered Species Act in 1999. Post-delisting monitoring for the Peregrine Falcon stipulated surveys of breeding locations and did not specifically emphasize other metrics of population dynamics such as survival. We used banding data from Peregrine Falcons captured on the Washington coast during 1212 vehicle surveys between 1995 and 2018 to assess apparent survival and resighting frequencies. Our mark-recapture data set included 226 Peregrine Falcons: 148 females and 78 males. Fourteen Peregrine Falcons were recovered dead and another eight were found injured or uninjured and unable to fly due to illness or substantially soiled feathers. We had 744 resightings, 67.1% (n = 499) by our research group during surveys (Group A) and 32.9% (n = 245) by others (Group B). We found a dramatic increase in Group B contributions beginning in 2008 due to the emergence of digital camera use in wildlife photography and increased public awareness of our project. Data from 1995 to 2018 supported the estimation of apparent survival for three age classes of Peregrine Falcons: 0.424 (SE = 0.057) for hatch-year (<1 yr old); 0.663 (SE = 0.066) for second-year (1–2 yr old), and 0.738 (SE = 0.030) for after-second-year (>2 yr old). Our long-term mark-resighting analyses of overwintering and migratory Peregrine Falcons along the Washington coast provide evidence of a reasonably high level of apparent survival that suggests good population performance.

Identifying migratory raptors' wintering areas and migration routes is an essential part of predicting their responses to habitat and climate change throughout their annual cycles, and therefore important for their conservation. Among the world's most widespread migratory species, the Peregrine Falcon (Falco peregrinus) has been the subject of intensive study on its breeding grounds and at some migratory stopover sites, but the links between its breeding, stopover, and wintering areas remain poorly known. In particular, few empirical data are available on migratory F. p. tundrius and F. p. anatum (hereafter, Nearctic peregrines) wintering in South America during the austral spring and summer. Here, we present evidence connecting Nearctic peregrines wintering in Peru with their natal and breeding territories in North America using mark-recapture data collected between 1963 and 2019. We documented eight encounters of banded wintering Nearctic peregrines, whose natal origins or breeding regions included the Northwest Territories, Nunavut, and Yukon Territory in Canada, and Alaska, Minnesota, and Nebraska in the USA. Our findings indicate that both tundrius and anatum peregrines winter in Peru and originate from a widespread geographic breeding range, corroborating other research suggesting that Nearctic peregrine migration is highly dispersive. Peregrines exhibit sex-related differential migration patterns in which males tend to migrate farther than females, and our data from the capture of 208 Nearctic peregrines suggest that the majority of wintering birds in Peru are males (n =150; 72%). We also report new records of Nearctic peregrine arrivals in Peru that represent advances of approximately 2–3 wk compared to the earliest previously published reports. The variability of peregrines' migratory movements may be related to the behavioral plasticity that facilitated their successful recovery following their catastrophic declines in much of North America. As peregrines remain vulnerable to human impacts including habitat and climate change, continuing to fill gaps in our knowledge of Nearctic peregrines' migratory connectivity will enable continuing conservation measures for these spectacular birds.

Birds show huge variation in color displays evolved for communication. However, among colored phenotypic traits, eyes remain largely overlooked, with only a few studies suggesting a potential signaling function or a role in mate recognition and crypsis. Iris color is a remarkably striking feature in the wholly cryptic pattern of many owls, and may potentially play a signaling function, a possibility so far neglected. Here, we studied variation and potential signaling of iris yellowness as an indicator of quality in parent-offspring communication and other social contexts in the Little Owl (Athene noctua) and Eurasian Scops-Owl (Otus scops). Yellowness did not differ between the sexes; however, adults of the two species had more intensely yellow irises than owlets. Most of variation in iris yellowness of owlets occurred between rather than within nests and seemed to be linked to parental qualities of Little Owls, but was unrelated to condition among Eurasian Scops-Owl owlets. In adults, however, we found that iris yellowness of females was positively associated with nest success (an index of female fitness) in Little Owls, but not in Eurasian Scops-Owls. This study suggests that iris color variation is unlikely to play a role in parent-offspring communication for these two owl species, but that iris yellowness of female Little Owls may potentially play a signaling role in social contexts, a possibility that should be studied in the future.

For more than three decades, a restored population of Ospreys (Pandion haliaetus) in the Minneapolis-St. Paul, Minnesota, metropolitan area has used artificial nesting structures nearly exclusively. Nests on opportunistically used structures (not originally intended for nesting) were higher, farther from lakes, and in locations with greater coverage of pavement and buildings than nests on structures provided specifically for Ospreys. The frequency of use of provided structures was best predicted by a linear model that incorporated the height of the nest, the height of the nearest tall tree or artificial structure, distances to the nearest tall tree/structure, road, and lake, and coverage of trees, water, and developed land within 200 m of the nest structure. Since 1995, nesting success has ranged from 61% to almost 90%, averaging 76%. Active nests (i.e., nests where eggs were laid) averaged 1.6 young fledged per nest since 1995. Adults typically used the same structure in successive years, with little change in productivity (i.e., the number of young produced per active nest) in successive years. However, a few adults that experienced lower productivity used different structures in the succeeding year with a marked increase in productivity. Productivity at nests on provided structures did not differ from that at nests on opportunistically used structures. Productivity was not related to characteristics of the nest structure or its vicinity.

Bald Eagle (Haliaeetus leucocephalus) populations have been recovering throughout North America for the past several decades, and long-term monitoring efforts have been useful for understanding the ecological and anthropogenic drivers that influence population trajectories. We analyzed data on Bald Eagles in Kansas over 30 breeding seasons (1989–2018) to describe population growth, habitat selection, temporal trends in productivity, and predictors of nesting attempts. The breeding Bald Eagle population in Kansas recovered from a single documented nesting pair in 1989 to 137 documented nesting pairs in 2018. Habitat in and around large artificial reservoirs was important for early colonizing nesting pairs. However, as the population grew, nesting territories along river shorelines made up a majority of the total. Birds nesting in territories near rivers and large artificial reservoirs, newer territories, and territories closer to electrical lines were significantly more likely to have a nesting attempt compared to those in other territories. Capture-mark-resighting efforts allowed us to track productivity, recruitment, and site fidelity for a portion of the breeding population in Kansas (272 banded individuals). Growth of the breeding Bald Eagle population in Kansas has shown little sign of slowing in the first three decades following recolonization. Continued annual increases in the number of new nesting territories indicate that the availability of suitable habitat does not appear to be limiting population growth.

As part of a project to introduce avian predators for biological pest control, we used hard and soft release methods to introduce Barn Owls (Tyto alba) in the urban area of Universiti Sains Malaysia in Penang, Malaysia. We tested five methods: (1) hard release of non-acclimated adults, (2) hard release of non-acclimated juveniles, (3) soft release of hand-reared fledglings, (4) soft release of acclimated juveniles, and (5) soft release of acclimated adults. We employed radio-tracking to analyze the success of all methods, and the movement and survival of some of the released birds. We analyzed regurgitated pellets to study the diet of the successfully introduced owls. All hard-released non-acclimated adults and non-acclimated juveniles left the study area within a few days after their release. Soft release of hand-reared fledglings was also unsuccessful, as we could only detect the radio-tracked owls for ≤10 d after their release. Of the nine acclimated juveniles that were soft released, one stayed within the study area for 25 d but eventually dispersed. The soft release using acclimated adults was the most successful release method, as 60% (3 of 5 birds) of the released owls were tracked for >30 d and became established as resident birds in the study area. We observed these adults roosting and hunting prey within the study area. Analysis of regurgitated pellets showed the resident Barn Owls preyed primarily on small mammals. Our results suggest that the most suitable method to introduce and establish Barn Owl populations in an urban area was by using soft release of acclimated adults.

We report on the morbidity and fate of 138 raptors of 27 species admitted to the Royal Society of the Conservation of Nature rehabilitation center in Jordan during 2017–2018. Peregrine Falcons (Falco peregrinus) made up the greatest percentage admitted (28.3%), followed by the Long-legged Buzzard (Buteo rufinus; 7.3%), Saker Falcon (Falco cherrug; 7.3%), Eurasian Eagle-Owl (Bubo bubo; 7.3%), and nine species represented by a single individual each. Confiscation due to illegal possession or transport (n = 81) was the most common reason for raptor admittance, followed by trauma (n = 26) and infections/disease (n = 26). Other major reasons for admittance included malnutrition (n =12) and orphaning (n =12). Twenty-six birds (18.8%), mostly falcons, were still in the rehabilitation center at the time of publication, and 22 (16%) individuals died during treatment due to their injuries (n =14) or severe Newcastle infections (n =8). Seventy-seven individuals were released into nature reserves, accounting for 55.8% of the total rehabilitated birds, and 13 individuals (9.4%) were returned to their owners.

Arthropod-borne viruses represent the most important emerging viruses worldwide. Saint Louis encephalitis (SLEV) and West Nile (WNV) viruses are vectored by Culex spp. mosquitoes and amplified by several bird species. We carried out an extensive retrospective serosurvey study to analyze the exposure of free-ranging raptors to SLEV and WNV in central Argentina. We collected samples from eight species of raptors between 2008 and 2015. We used Plaque Reduction Neutralization Tests (PRNT) to analyze 523 plasma samples for both viruses. Of the individuals tested for WNV, 85.2% of the Swainson's Hawks (Buteo swainsoni) were positive. Fewer birds presented neutralizing antibodies against SLEV: 20.8% of the Black Vultures (Coragyps atratus), 25% of the Southern Caracaras (Caracara plancus), and 0.3% of the American Kestrels (Falco sparverius). One Swainson's Hawk was positive for both viruses. We found no neutralizing antibodies in samples from Turkey Vultures (Cathartes aura), Chimango Caracaras (Phalcoboenus chimango), Burrowing Owls (Athene cunicularia), and a Ferruginous Pygmy-Owl (Glaucidium brasilianum). Although seroprevalence varied among species, our results confirmed SLEV and WNV circulation in resident and migratory populations of raptors in central Argentina. These findings suggest the need for further studies regarding circulation and ecological characterization of these viruses in bird communities in Argentina.

In recent years, several phylogenetic studies on the genus Buteo have been conducted. However, little is known about the lineage of the Eastern Buzzard (Buteo japonicus). We sequenced 919-bp fragments of mtDNA from 45 Eastern Buzzards from Japan and compared them with the sequences of the genus Buteo registered in the DDBJ/EMBL/GenBank databases. ND6 and pseudo control region phylogenetic analyses were performed on 15 and 35 specimens in the database, respectively. All 45 Eastern Buzzards from Japan possessed the same novel sequence in the ND6 gene, which differed in four base pairs from sequences previously reported for the Eastern Buzzard from continental Asia. Phylogenetic analysis of the ND6 gene showed that Japanese birds with the novel sequence did not form a clade with those from continental Asia with the previously reported sequences; instead, the continental Eastern Buzzard formed a clade with Himalayan Buzzards (Buteo refectus). A phylogenetic tree constructed using pseudo control region sequences showed that Eastern Buzzards were divided into two groups: one containing the Himalayan Buzzard, and one containing birds with the novel sequence. Our results suggested that the novel sequence revealed in this study is a geographic variant that may represent the “true” Eastern Buzzard, and that the previously reported sequence (from continental Asia) is that of the Himalayan Buzzard. We suggest that it is necessary to examine the habitats and characteristics of Eastern and Himalayan Buzzards in eastern Eurasia to more accurately classify these birds.

Animal perception of risk and response to vehicle approach affect survival. We quantified American Kestrel (Falco sparverius) behavioral response to aircraft approach in an airport environment, by examining the likelihood of initiating escape, flight-initiation distance (FID), and the type of escape response. We observed 32 American Kestrel-aircraft interactions at Burke Lakefront Airport in Cleveland, Ohio, USA, from June 2015 through September 2016. American Kestrels responded to aircraft by initiating escape (i.e., FID > 0) 34% of the time, with a mean FID of 64 m and frequent (82%) returns to the same location occupied before the escape. Based on effect size estimates, the trajectory of an aircraft approach (direct vs. nondirect) was a more important determinant of whether an American Kestrel initiated escape than was the type of aircraft (propeller or piston vs. jet-powered). Assuming an average aircraft ground speed of 51.4 m/sec on landing phase, birds responded on average 1.2 sec before an aircraft was over or at the bird's position. Based on the relationship among likelihood of initiating escape, FID, and reported bird-aircraft collisions (strikes) across species studied at the same airport, American Kestrels followed a strategy of relatively low likelihood of initiating escape and short FIDs, which led to infrequent strikes. However, compared to American Kestrels, some other species that followed a similar strategy had more aircraft strikes, whereas some species with different strategies experienced similar numbers of strikes. This variation among species in escape strategies and strikes should be studied further, as it could lead to new ways of modeling bird-strike risk at airports.

Nest boxes are a popular tool for research and conservation of American Kestrels (Falco sparverius; hereafter “kestrel”). The size of nest box entrance holes affects occupancy, interspecific competition, and nest predation for a number of bird species, but effects on prey delivery success are unstudied. We used digital video cameras to monitor kestrels using two nest box designs, one with a small circular entrance hole (8.75 cm in diameter; n = 8) and the other with a large U-shaped entrance hole (7.62 cm wide by 12.07 cm high; n = 6), to compare the rates at which kestrels failed to deliver large prey (vertebrates) into the nest box while provisioning nestlings. Across 111 d of monitoring, we observed a significantly higher prey delivery failure rate at the boxes with small holes (8.9%) compared to boxes with large holes (1.6%). Boxes with small holes fledged 4.33 nestlings and boxes with large holes fledged 4.5. These results suggest that kestrels nesting in boxes with small entrance holes may have higher costs while provisioning nestlings, compared to kestrels using boxes with larger entrance holes. We conclude that the ideal entrance hole size for kestrel nest boxes may be a compromise between being small enough to minimize predation, yet large enough to allow kestrels with large prey to easily enter. Future research should investigate whether boxes with higher prey delivery failure rates have lower reproductive success.

Sex identification is an important research topic in avian ecology because easy and accurate sex identification is useful for studies of evolution, behavior, and population dynamics. We used field photographs to measure the markings on the tail feathers of adult Grey-faced Buzzards (Butastur indicus) breeding in Japan to elucidate the attributes that allow individual sex determination. We labeled the dark, horizontal bands B1, B2, and B3, starting from the tip of the tail feathers and proceeding toward the base; we designated the light, horizontal band between B1 and B2 as W1, and the light, horizontal band between B2 and B3 as W2. To clarify the difference between the tail feathers of the sexes, we measured the ratio of W2 to W1 (W2/W1) of the right tail feather 3, right tail feather 4, left tail feather 3, and left tail feather 4, and calculated the average of these four values (average W2/ W1). We tested these ratios using the Brunner-Munzel test to determine whether they discriminated the sexes. We found that the four individual feather ratios differed significantly between males and females. In addition, males and females could be reliably distinguished using the average W2/W1. This method can be widely used for fast, non-invasive sexing of Grey-faced Buzzards because it does not require sophisticated techniques.