Little is known about the ecology of the Grey-headed Fish-Eagle (GHFE; Ichthyophaga ichthyaetus) despite it being a globally near-threatened species in apparent decline. We here present the first quantitative information on nesting ecology of this species, in a regionally significant population at Prek Toal, part of the seasonally flooded swamp forest surrounding the Tonle Sap Lake, Cambodia. We found that GHFE selected trees as nest sites that had an open crown structure and were relatively tall. Grey-headed Fish-Eagles preferred nesting closer to permanent water than expected, but the timing of breeding did not differ according to distance to permanent water: we suggest that their preference for nests near water may reflect an advantage based on prey availability. Water snakes, known prey of GHFE, were significantly more abundant at a site in permanent water than at a temporarily flooded site, in December. We also found that human habitation was negatively correlated to GHFE nest-site occupancy rates. This may reflect indirect effects of human exploitation of GHFE food supplies, which may be exacerbated in the future by changes to the Tonle Sap ecosystem resulting from upstream dam construction.

We conducted repeated aerial surveys for breeding cliff-nesting raptors on the Yukon Delta National Wildlife Refuge (YDNWR) in western Alaska to estimate detection probabilities of Gyrfalcons (Falco rusticolus), Golden Eagles (Aquila chrysaetos), Rough-legged Hawks (Buteo lagopus), and also Common Ravens (Corvus corax). Using the program PRESENCE, we modeled detection histories of each species based on single species occupancy modeling. We used different observers during four helicopter replicate surveys in the Kilbuck Mountains and five fixed-wing replicate surveys in the Ingakslugwat Hills near Bethel, AK. During helicopter surveys, Gyrfalcons had the highest detection probability estimate (;  =  0.79; SE 0.05), followed by Golden Eagles (  =  0.68; SE 0.05), Common Ravens (  =  0.45; SE 0.17), and Rough-legged Hawks (  =  0.10; SE 0.11). Detection probabilities from fixed-wing aircraft in the Ingakslugwat Hills were similar to those from the helicopter in the Kilbuck Mountains for Gyrfalcons and Golden Eagles, but were higher for Common Ravens (  =  0.85; SE 0.06) and Rough-legged Hawks (  =  0.42; SE 0.07). Fixed-wing aircraft provided detection probability estimates and SEs in the Ingakslugwat Hills similar to or better than those from helicopter surveys in the Kilbucks and should be considered for future cliff-nesting raptor surveys where safe, low-altitude flight is possible. Overall, detection probability varied by observer experience and in some cases, by study area/aircraft type.

Little is known about the abundance and distribution of Chinese Goshawks (Accipiter soloensis) during spring migration along the Western Pacific flyway around Taiwan. This species is the most numerous migratory raptor in East Asia. In April 2004, we employed weather radar at Kenting and Chiku to study the spatial and temporal distribution and flying behavior of migrants in the Taiwan area. Goshawk flocks migrating across Luzon Strait toward Taiwan (n  =  193) averaged 3.1 km in length (SD  =  3.41, range 1.0–27.5 km) and 0.7 km in width (SD  =  0.30, range 0.3–2.5 km). Using a regression model relating bird numbers to the reflectivity of radar images, we estimated that at least 225 935 Chinese Goshawks passed through the study area during 5 d in the month of April. Flocks crossing the Luzon Strait approached the Hengchun Peninsula, at the southern tip of Taiwan, along several inland and offshore routes, making it difficult to obtain accurate and complete observations from the ground. Farther north at Chiku, we used radar imaging to estimate 150 619 northbound migrants, 67% of the number detected by the Kenting radar. Of these, 24% bypassed Taiwan and flew nonstop to mainland China via the Pescadores, located off the west coast of Taiwan. Another 55% flew over the southern end of Taiwan and then across the Taiwan Strait to the mainland. The remaining 21% continued north over Taiwan after spending up to 2 d in the central mountains of Taiwan. This likely explains why relatively small numbers of goshawks are observed in central and northern Taiwan. Chinese Goshawks flew more slowly and higher over land than over water, and their ground speed increased with favorable winds.

The breeding distribution of the Upland Buzzard (Buteo hemilasius) is restricted to the eastern Palearctic. In comparison to other Buteo species, little is known about this species' breeding ecology. The objectives of our study were to describe nest sites and reproductive success of Upland Buzzards in Mongolia. The average clutch size for 304 breeding attempts in 2001–07 was 3.49 eggs (±1.09 SD; range 2–8; total of 1061 eggs laid). For 215 breeding attempts, the average brood size was 1.95 nestlings (±1.53; range 0–6). We found that the nest materials and nest size varied greatly, probably corresponding to the availability of nesting materials within the territory. However, the variation in nest size may also reflect the fact that some of the smaller nests were built on human-made structures, such as electric pylons or roofs of small buildings.

Although the White-tailed Kite (Elanus leucurus) is widely distributed throughout the Americas, winter communal roosting has been recorded only in the Nearctic portion of its range. As a result, data on the food habits of the White-tailed Kite in South America during the nonbreeding season are scarce and, when available, limited to pellets from solitary individuals. Here, we report the communal roosting behavior and the winter diet of White-tailed Kites in an agricultural habitat on the Argentine pampas based on information gathered over three consecutive years (2006–2008). From May to July of each year, we observed an average of 11 (±SD  =  2.8) kites roosting in a grove of Eucalyptus viminalis. Prior to roosting, kites gathered in a tall, dead, and leafless Eucalyptus tree before flying to more densely foliated trees where they spent the night. The diet of kites during winter was composed almost entirely of small mammals, mainly Calomys sp. and Akodon azarae. Because agricultural intensification in the Argentine pampas is ongoing, further studies are needed to gain a complete knowledge of White-tailed Kites in this habitat and of the effects of land-use changes on their foraging and other behavior.

Endoparasites of raptors are rarely documented to cause pathogenecity. We examined 60 live and 5 salvaged Swallow-tailed Kites (Elanoides forficatus) for gastrointestinal parasites. Methods included screening excreta collected from nestling and adult kites and their nests and dissecting the alimentary canals of salvaged nestlings. Kites hosted the following helminths (nematodes: Dispharynx sp., Procyrnea sp., and an immature ascarid; trematodes: Order Strigeatida; cestodes: Taenia vexata; acanthocephalan: Centrorhynchus spinosus), and two taxa of protozoans (Phylum Sporozoa: unidentified coccidia; and Phylum Metamonada: Giardia sp.). Two of 43 nestlings we examined during banding hosted larval Protocalliphora sp. (Diptera: Calliphoridae). Helminth prevalence was 27.7%, with trematodes and nematodes being most prevalent, 13.8% and 10.8% respectively (n  =  65). The prevalence of Dispharynx sp. in first-year kites was 11.5% (n  =  52). Dispharynx sp. caused stomach lesions in two first-year kites.

Infectious diseases can potentially affect the seasonal migration of hawks. We tested three species of California hawks from autumn 2004 to spring 2006 for haemosporidian blood parasites (Plasmodium, Haemoproteus, and Leucocytozoon spp.). We screened 323 Red-tailed Hawks (Buteo jamaicensis), 100 Cooper's Hawks (Accipiter cooperii), and 21 Red-shouldered Hawks (B. lineatus) for blood parasites using polymerase chain reaction (PCR). Among these hawks, 221 (50%) were infected with Haemoproteus, 134 (30%) with Leucocytozoon, and none with Plasmodium species. We compared blood parasite prevalence results to identify infection patterns in two populations (birds captured during autumn at a migration watchsite in the Marin Headlands [Golden Gate Raptor Observatory] vs. birds captured during winter in the Central Valley) and between years, seasonal periods, and sex and age classes. In 2004, Marin Red-tailed Hawks were more likely to test positive for blood parasites if sampled late in the migration; however, we observed the opposite pattern in Cooper's Hawks. The prevalence of both Haemoproteus and Leucocytozoon followed the same seasonal trends in each host species, which suggested a possible effect of infection status on raptor migration. We also observed different patterns of variation in parasite prevalence between years at the two sampling sites, but no significant differences between juvenile and adult birds at either site. In addition, using a simple measure of body condition, we observed significant differences between males and females with regard to the effects of parasite infection and sampling location. These results provide a baseline for future studies monitoring long-term changes in parasite prevalence and effects on California's migrating hawks.