We estimated relative abundance and density of Western Burrowing Owls (Athene cunicularia hypugaea) at two sites in the Mojave Desert (2003–04). We made modifications to previously established Burrowing Owl survey techniques for use in desert shrublands and evaluated several factors that might influence the detection of owls. We tested the effectiveness of the call-broadcast technique for surveying this species, the efficiency of this technique at early and late breeding stages, and the effectiveness of various numbers of vocalization intervals during broadcasting sessions. Only 1 (3%) of 31 initial (new) owl responses was detected during passive-listening sessions. We found that surveying early in the nesting season was more likely to produce new owl detections compared to surveying later in the nesting season. New owls detected during each of the three vocalization intervals (each consisting of 30 sec of vocalizations followed by 30 sec of silence) of our broadcasting session were similar (37%, 40%, and 23%; n  =  30). We used a combination of detection trials (sighting probability) and double-observer method to estimate the components of detection probability, i.e., availability and perception. Availability for all sites and years, as determined by detection trials, ranged from 46.1%–58.2%. Relative abundance, measured as frequency of occurrence and defined as the proportion of surveys with at least one owl, ranged from 19.2%–32.0% for both sites and years. Density at our eastern Mojave Desert site was estimated at 0.09 ± 0.01 (SE) owl territories/km² and 0.16 ± 0.02 (SE) owl territories/km² during 2003 and 2004, respectively. In our southern Mojave Desert site, density estimates were 0.09 ± 0.02 (SE) owl territories/km² and 0.08 ± 0.02 (SE) owl territories/km² during 2004 and 2005, respectively.

The Papuan Harrier (Circus spilonotus spilothorax), currently classified as a subspecies of the Eastern Marsh-Harrier (C. spilonotus), is endemic to the island of New Guinea and may be in need of conservation attention because of threats from grassland burning. I here detail the discovery of the first known nests in lowland Papua New Guinea and provide egg dimensions and prey data. Both nests were initiated in early April, in damp rank grassland, and contained three small chicks in mid-May. The only egg measurements, combined with one previously published record, suggest large egg volume and concomitant large female body size (estimated to be ca. 890 g). At this size, this may be the world's largest harrier. Fire destroyed both nests within 5 wk of their discovery. An atypically slow foraging style and a preponderance of game birds and large rats (Rattus spp.) in the pellets and prey remains are consistent with large body size. Further studies of the bird's ecology and breeding are needed for a comprehensive understanding of its conservation status and threats to its population.

From 1980 to 1998, Washington's Bald Eagle (Haliaeetus leucocephalus) population increased at an annual rate of 10%. Over the same time period, foraging activity of Bald Eagles at marine bird breeding colonies also increased. From 1993 to 2008, we observed foraging-related behavior of Bald Eagles on Violet Point, Protection Island. This island hosts more than 70% of the breeding seabirds in Washington's inner seaways and serves as an important rookery for harbor seals (Phoca vitulina). We found that (1) eagles landed more frequently in seal haul-out (beach) areas than in gull-nesting (non-beach) areas of Violet Point, and that subadult eagles were more likely to land in gull-nesting areas than were adult eagles; (2) the presence of eagles on the beach was positively related to the presence of harbor seals on the beach; (3) a greater-than-expected number of adult eagles as compared with subadult eagles preyed on gull chicks; (4) subadult and adult eagles that attempted prey capture were equally successful at snatching gull chicks from the gull colony; (5) eagles were more likely to prey on gull eggs in tall grass than on gull eggs in sparse vegetation. Prey remains beneath one eagle nest on the island did not accurately reflect the range and relative frequencies of observed eagle predation events. Although seal afterbirths and dead pups constitute a major component of the diet of Bald Eagles on the island, the effect of eagles on live seals is probably negligible. In contrast, direct predation and indirect effects of eagle activity on Glaucous-winged Gull (Larus glaucescens) reproductive success may be substantial and may have been partly responsible for a 44% decrease in the number of gull nests in the colony from 1993–2008.

We studied the causes of raptor admissions to the only wildlife rehabilitation center on the largest island of the Canarian Archipelago (Tenerife) over ten years (1998–2007). A total of 2611 birds of prey, belonging to nine falconiform diurnal raptor and four strigiform species, were admitted. The Eurasian Kestrel (Falco tinnunculus) and the Long-eared Owl (Asio otus) were the species most commonly admitted and jointly made up 85.6% of admissions. The most frequent causes of admission to the wildlife rehabilitation center were collisions (with cars, high-voltage electric transmission towers, etc.; 42.2%), starvation (5.1%) and entanglement in glue traps intended for rodents (4.7%). Poisoning and shooting were recorded for 2.4 and 1.5% of the birds admitted, respectively. Only collisions increased during the study period. A total of 1010 birds (44.4% of the total) were released to the wild following rehabilitation. We recommend more financial support for rehabilitation centers to develop detailed analytical diagnoses and rehabilitation services.

The Boreal Owl (Aegolius funereus) is a nocturnal forest-dwelling species widely distributed throughout the world. One of the least studied and most southerly populations of this species lives in the Pyrenees Mountains. This population, 500–600 pairs, probably suffered a slight decline during recent decades due to forestry management practices. The use of nest boxes may become necessary to protect this species in southern Europe. The objective of this study was to establish a standard protocol for nest-box installation, based on the analysis of occupation rates of nest boxes installed during the last 20 yr and the comparison of reproductive data for nest boxes and natural nest cavities. Our results indicated that nest boxes should be installed at high elevations (above 2000 m asl), below 4 m aboveground, and preferably facing south or southeast. We also found that most territories are located where maximum July temperatures are <17°C, which suggests that increasing temperatures due to climate change may have a negative effect on this population.

Recent concern about the decline of the Little Eagle (Hieraaetus morphnoides) in southeastern Australia has raised questions about whether Wedge-tailed Eagles (Aquila audax) might be implicated in this decline. The ecology, including the diet, of Little Eagles is rather poorly known. The diet of the Wedge-tailed Eagle is better documented, but the overlap in prey used by the two eagles has been little studied. Near Canberra between July 2002 and January 2008, we identified 1421 and 192 prey items from nests of Wedge-tailed Eagles and Little Eagles, respectively. Wedge-tailed Eagles' diet was similar to that reported elsewhere. In addition to European rabbits (Oryctolagus cuniculus), Little Eagles specialized on birds, but tended to avoid macropods, a main prey of Wedge-tailed Eagles, and there was little overlap in prey used by the two eagle species. Although Standardised Food Niche Breadth and Shannon Diversity Index were similar for the two eagles, Wedge-tailed Eagles captured significantly larger prey, as indicated by the difference in Geometric Mean Prey Weight, 1298 g for Wedge-tailed Eagles and 249 g for Little Eagles, which reflected the fivefold difference in mass between male Little Eagles and male Wedge-tailed Eagles. We suggest that direct competition for prey probably was not the cause of the Little Eagle decline.