Cooper's Hawks (Accipiter cooperii) have recently colonized many urban landscapes across North America, but data on breeding densities and trends in densities of these populations are lacking. We surveyed for woodland raptors throughout approximately 1000 km² in the metropolitan Milwaukee, Wisconsin, area over a 21-yr period, 1988–2008. We documented the natural colonization of this urban landscape by a pioneer Cooper's Hawk population and its subsequent growth from 1993–2008 (4 to 41 laying pairs, 4 to 55 occupied sites). Nearest-nest distances decreased and the number of Cooper's Hawk laying pairs increased while nesting surveys remained consistent temporally and spatially, indicating that density of breeding pairs was increasing in the metropolitan Milwaukee area. Approximately 15 yr after initial colonization, the breeding density of Cooper's Hawks in some localized areas averaged one laying pair per 330 ha (range: 68–587 ha). From 1996–2008, as breeding density increased, average annual productivity (number of young/laying pair) for Cooper's Hawks in Milwaukee County, a subset of the overall larger metropolitan study area, also increased. During the early years of colonization, a relatively high proportion of individuals or pairs of birds appeared to occupy nest sites but did not breed. Younger birds may have played a role in the colonization of this urban landscape. This population was likely increasing at a relatively rapid rate during the late 1990s and continued to increase throughout the remainder of our study.

Concern for the welfare of animals used in research and teaching has increased over the last 50 yr. Animal welfare legislation has resulted in guidelines for the use of animals in research, but the guidelines can be problematic because they focus on animals used in laboratory and agriculture research. Raptor biologists can be constrained by guidelines, restrictions, and oversight that were not intended for field research methods or wild animals in the wild or captivity. Field researchers can be further hampered by not understanding animal welfare legislation, who is subject to oversight, or that oversight is often provided by a committee consisting primarily of scientists who work with laboratory animals. Raptor researchers in particular may experience difficulty obtaining approval due to use of various species-specific trapping and handling methods. We provide a brief review of animal welfare legislation and describe the basic components and responsibilities of an Institutional Animal Care and Use Committee (IACUC) in the United States. We identify topics in raptor research that are especially problematic to obtaining IACUC approval, and we provide insight on how to address these issues. Finally, we suggest that all raptor researchers, regardless of legal requirements, abide by the spirit of the animal welfare principles. Failure to do so may bring about further regulatory and permitting restrictions.

In some portions of their range, Mexican Spotted Owls (Strix occidentalis lucida) are found occupying conifer-dominated forests, whereas in other portions of their range, they occupy narrow and steep-walled canyons. Although the characteristics of this owl's nesting and roosting habitat have been studied extensively in predominately forested environments, there is far less information describing microhabitat features associated with nesting and roosting sites in canyon systems. In this report, we quantitatively describe microhabitat characteristics of nest and roost sites of Mexican Spotted Owls within the Guadalupe Mountains of southeastern New Mexico and west Texas, where Spotted Owls dwell primarily in narrow, rocky, and semiarid canyons. We measured 21 habitat features describing the geomorphology of the canyon and finer-scaled variables at accessible owl nest or roost sites (n  =  10) and at nearby random sites up- (n  =  10) and down-canyon (n  =  10); we found that tree canopy cover (%) was significantly higher at nest and roost sites than at down-canyon random sites, and percent cover of saplings and rocky debris was significantly (P < 0.05) greater at nest and roost sites than at up-canyon and down-canyon random sites. Our findings matched some of the results of previous studies conducted in canyonlands in Utah, Arizona, and Colorado but also differed in some respects.

We examined factors that influenced the presence of nesting Western Burrowing Owls (Athene cunicularia hypugaea) along roadsides and irrigation water-conveyance systems within an intensive agricultural area in Imperial Valley, southeastern California. We conducted walking line-transect surveys along randomly selected 1-km segments of roads to examine the types of roadside attributes and agricultural crops that were associated with the presence of nesting Burrowing Owls. Occupied burrows were more likely to be located along roadsides adjacent to fields where crops were present, but we found no obvious association with any particular type of crop. However, the type (concrete delivery canal or earthen drainage ditch), number, and location of irrigation trenches between the road and the agricultural field affected the likelihood of detecting owl nests. We failed to detect any effect of trench depth or whether the road was paved on the presence of Burrowing Owls. We found more occupied burrows on roads running north/south than on those going east/west. Our results suggest that water delivery methods, trench construction, and maintenance practices affect suitability of agricultural areas for Burrowing Owls in the Imperial Valley of California.

The winter destination of Burrowing Owls (Athene cunicularia) that breed in Canada is poorly understood. We flew 166.7 hr in a fixed-wing CESSNA 172, searching southern Texas and the Gulf Coast lowlands and central Mexico for signals from 125 VHF transmitters that were attached to Burrowing Owls in Canada in 1997, 1998, and 2000. Nine owls were located between Houston, Texas, and Michoacán, Mexico. The diurnal roosts used by the owls included vegetation, natural burrows, and a woodpile. Land-cover types around roosts were highly variable and less open than breeding habitat in Canada, but always included at least 35% low vegetation within 1 km of roosts.

Researchers banded 4439 Northern Saw-whet Owls (Aegolius acadicus) during autumn at 10 migration-monitoring stations between 2002 and 2007 in Alberta and Saskatchewan, Canada. Sixty-one recaptures of live birds or recoveries of dead birds (together termed “encounters”) banded at these stations and recaptures at these stations of birds banded elsewhere occurred during this period. The farthest saw-whet owl encountered was 2315 km from the banding station (Last Mountain Lake, Saskatchewan, to Hebron, Pennsylvania). Almost half of the encounter locations were east or southeast of the associated banding site. The overall average speed of within-season travel was 37 km/night; however, the average speed of eastward movements was 81 km/night (n  =  9). Of 19 within-season (mid-August to mid-December) encounters, hatch-year females (n  =  11) travelled farther (615 km ± 464.9) than after-hatch-year females (n  =  5; 110 km ± 33.6; P  =  0.047). Three owls apparently overwintered in Alberta and Saskatchewan. During the nonbreeding season, saw-whet owls in Alberta and Saskatchewan may employ more than one movement strategy, including migration, overwintering in the region, and possible nomadism, which suggests that the species is a variable partial migrant. Birds banded at Alberta stations had more southward encounters than those banded at Saskatchewan stations, which were encountered mostly to the southeast, suggesting that autumn movements of saw-whet owl are influenced by the presence of suitable forested habitat.