Boreal Owls (Aegolius funereus) rely on mature forests and, consequently, are negatively affected by timber harvesting strategies that alter the composition and structure of these forests. We tested an existing Boreal Owl habitat suitability index (HSI) model created using data from across the species' North American breeding distribution, plus a modified Newfoundland version that incorporated local data. We assessed the applicability of these models to a population on the periphery of the species' North American range in Newfoundland, Canada. We also conducted habitat composition analyses and evaluated the Boreal Owl HSI model values associated with forest cover projections under three different forest harvesting scenarios. Overall output from both HSI models indicated low levels of suitability for locations across the study area. Long-term persistence in Newfoundland demonstrates that suitable habitat for Boreal Owls exists, but what constitutes suitable habitat for populations in other parts of North America may differ from that in our study area. Boreal Owls in Newfoundland occupied locations with a greater proportion of disturbed cover, and lesser proportions of deciduous and mixed coniferous and deciduous stands ≥60 yr old, compared to what was available in the surrounding region, as measured in randomly selected plots. Whereas Boreal Owl habitat use in Newfoundland was similar to that described for other populations, the limited use of deciduous and mixed stands was distinct. Forward projection modeling of forest cover indicated that there were no differences in the overall suitability of habitat available to Boreal Owls under the three harvesting scenarios. Our study highlights the importance of adjusting forest management strategies to account for differences in habitat use among populations.

In recent years, anthropogenic conversion of grassland habitat has raised concerns about the status of breeding Swainson's Hawks (Buteo swainsoni) in the northern Great Plains region of North America. During 2013–2014, we captured breeding Swainson's Hawks in north-central South Dakota and south-central North Dakota to estimate home-range size, determine adult survival rates during the breeding season, and evaluate habitat selection. We captured, radio-tagged, and monitored 13 Swainson's Hawks in 2013, and captured two additional Swainson's Hawks in 2014. In 2014, seven of 13 individuals initially captured in 2013 returned to the same breeding territory for the 2014 breeding season. Average 95% MCP home-range size in 2013 was 205.4 ha (SD = 135.3 ha, n = 10) and 211.1 ha (SD = 208.8 ha, n = 9) in 2014, and size did not differ between years (t₁₃ = 0.07, P = 0.95), averaging 208.3 ha (SD = 244.9 ha, n = 19 home ranges measured for 12 birds) for the 2 yr of the study. Mean core home-range size (50% MCP) was 78.2 ha (SD =105.9 ha, n = 10) in 2013 and 59.7 ha (SD = 80.7 ha, n = 9) in 2014; core home-range areas also did not differ between years (t₁₇ = −0.46, P = 0.65). Swainson's Hawks did not select habitats in proportion to their availability in 2013 (χ²₄₂ = 781.99, P < 0.001) and 2014 (χ²₄₀ > 999.99, P < 0.001). In 2013, breeding Swainson's Hawks selected against wetland and grassland habitats and selected for trees as foraging habitats. Similarly, Swainson's Hawks selected against grassland habitats for foraging in 2014. We used known-fate analysis in Program MARK to estimate adult survival during the breeding season. The top-ranked model indicated survival was constant at 0.94 (95% CI = 0.68–0.99) during the breeding season and did not differ between years. Our results suggest that Swainson's Hawks maintain a moderately high degree of breeding-site fidelity and have home ranges smaller than those documented elsewhere, and that their home-range size is influenced positively by the presence of grasslands and negatively by development.

Movement and space use are important components of animal interactions with the environment. However, for hard-to-monitor raptor species, there are substantial gaps in our understanding of these key determinants. We used noninvasive genetic tools to evaluate the details of space use over a 3-yr period by White-tailed Eagles (Haliaeetus albicilla) at the Naurzum Zapovednik in northern Kazakhstan. We genotyped, at 10 microsatellite markers and one mitochondrial marker, 859 eagle feathers and assigned naturally shed feathers to individuals. We identified 124 White-tailed Eagles, including both members of 5–10 pairs per year, and were able to monitor birds across years. Distances between eagle nests and hunting perches were always greater than nearest neighbor distances, eagles never used the closest available hunting perch, and hunting perches were always shared with other eagles. When eagles switched nests between years, the nests they chose were almost always well outside the space that theory predicted they defended the prior year. Our data are inconsistent with classical territorial and colonial models of resource use; they more closely resemble semi-colonial behavior. It is unlikely that standard methods of animal tracking (e.g., marking and telemetry), would have provided a similarly cost-effective mechanism to gain these insights into spatial and temporal aspects of eagle behavior. When combined with existing information on space use of other local species, these data suggest that partitioning of spatial resources among White-tailed Eagles and other eagles at the Zapovednik may be facilitated by the alternative strategies of space use they employ.

Contemporary declines of shorebirds have been linked to environmental causes, but the role of predation in shorebird declines is not clear. From 1994 to 2015, we observed the interactions of Peregrine Falcons (Falco peregrinus) and Dunlin (Calidris alpina) wintering on the Pacific coast of British Columbia. Peregrine sightings per hour of observation declined on a seasonal basis from October to February, but increased chronologically from 0.36/hr in 1994 to 1.24/hr in 2015. Peregrines captured 205 Dunlin in 1369 attacks. Hunting success rates increased from 10.8% in October to 15.0% in the winter months. During high tide, when the intertidal zone was flooded, some Dunlin flocks spent up to 315 min in sustained flight over the ocean, apparently as an antipredator strategy, but other flocks roosted on the foreshore, or sat out the high-tide interval on agricultural fields inland. This study suggests that these anti-predator behaviors allow the Dunlin population to persist at Boundary Bay as predator numbers increase.

Bar patterns on flight feathers of Great Gray Owls (Strix nebulosa) and Snowy Owls (Bubo scandiacus) are variable, and can be used to recognize individual birds. Here I illustrate a method for taking photos of wings of captured owls and describe a way to arrange images of flying birds for comparison with photos of birds in flight or in the hand. I report four examples. First, two Great Gray Owls photographed in flight on different days at the same site were shown to be the same individual, but differed from a dead owl found at that location a month later. Second, I compared eight photographs of wintering Snowy Owls in flight in Saskatchewan and determined that they portrayed seven different owls. Third, I examined photos of breeding male first-year Great Gray Owls at neighboring nest sites and established that they were different birds. Finally, I compared photos of breeding female Great Gray Owls at the same nest site in 2011 and 2013, and determined that they showed two individuals. I suggest that such photography may be used as a tool to census populations of Great Gray Owls and Snowy Owls.

Like many owl species, Sunda Scops-Owls (Otus lempiji) are difficult to monitor using traditional survey techniques, because of their nocturnal habits, secretive nature, and cryptic coloration. Individual variation in vocalizations could potentially be used to distinguish individuals of this owl species, as has been demonstrated for many bird species. The objectives of this study were to describe the territorial call of Sunda Scops-Owls, to determine whether the calls can be distinguished individually, and to examine whether the calls from the same individuals were stable over time. We analyzed 75 recordings collected from 12 owls from December 2014 to June 2015 in a lowland forest and oil palm smallholdings in Selangor State, Peninsular Malaysia. Using two temporal parameters and six frequency parameters derived from spectrogram, we employed ANOVA tests and found significant differences for all parameters among individual owls. Discriminant function analysis correctly classified 97.1% of the owl calls to the correct individuals. Based on the Wilcoxon signed-rank test, all vocal parameters did not vary significantly for the six birds that were vocally active over two predetermined survey sessions within the breeding period. Our results demonstrated that Sunda Scops-Owls can be identified individually by their vocalizations. This implies that assessing vocal individuality can be useful as a noninvasive method for surveying the Sunda Scops-Owls and the method should be further tested for other little-known owl species in the tropics.

On the Farallon Islands, 48 km west of the coast of central California, Burrowing Owls (Athene cunicularia) are a native migrant and a predator of the nonnative house mouse (Mus musculus) and the native Ashy Storm-Petrel (Oceanodroma homochroa). Previous research showed that Burrowing Owl predation on Ashy Storm-Petrels is likely unnaturally exacerbated by the abundance of house mouse prey in the fall, which may encourage more owls to overwinter. When the cyclic mouse population crashes in winter, the owls switch to preying upon the storm-petrels, a species of conservation concern. From September 2010 to May 2011, we conducted daily owl surveys and a diet study of Burrowing Owls on Southeast Farallon Island. One goal was to document seasonal changes in Burrowing Owl diet composition through collection and assessment of pellets. During our study period, 12 banded owls overwintered for an average of 118 d and contributed 64% of the 679 analyzed owl pellets. Insects were the most numerous prey item detected in pellets, but mice and storm-petrels made up 98.5% of the total prey biomass in the diet. Mouse consumption correlated positively with mouse abundance, and owls exhibited seasonal prey-switching behavior from mice to storm-petrels, when mouse abundance declined during the winter. Our findings suggest that a mouse eradication program on the Farallon Islands would result in fewer owls overwintering and subsequently reduce negative effects on the storm-petrel population.

Little is known of how territoriality of tropical forest raptors may be influenced by habitat reduction or fragmentation. We compared territory size and territorial defense behavior of Collared Forest-Falcons (Micrastur semitorquatus) in four 2500-ha survey quadrants with differing percent cover of tropical moist forest in a modified landscape in east-central Mexico. We delineated territories of Collared Forest-Falcons using playbacks of a simulated intruder, and calculated territory size and core area size using GIS. We also measured latency, duration, and type of territorial response of falcons to playbacks. We estimated a mean territory size of 205.5 ± 98.7 ha for seven Collared Forest-Falcons, although territories were significantly larger in low-forest-cover landscapes (mean 288.6 ± 76.9 ha), compared to those with high forest cover (mean 143.1 ± 58.3 ha). Collared Forest-Falcons showed stronger territorial behavior when defending territories with greater forest cover, responding for a longer time (5.9 ± 3.3 min), and including vocalizations with flights toward the speaker, compared to territories with low forest cover, where falcons mainly vocalized for 2 ± 1.1 min. Our results suggest that the Collared Forest-Falcon is sensitive to the extent of forest cover in the landscape, compensating for reduced forest cover by expanding the area defended, but investing less in defense of this area. This may have long-term implications for the acquisition of resources such as nest sites, and population dynamics of Collared Forest-Falcons in areas of reduced forest cover.

The index includes references to general topics, common names, keywords, and authors. Reference is also made to book reviews and letters. Taxa other than raptors are included where referenced by authors.