Northern Goshawk Home Ranges and Habitat Selection in the Great Basin of Southern Idaho

CHAPTER 1: NORTHERN GOSHAWK HOME RANGE CHARACTERISTICS IN SOUTH CENTRAL IDAHO To measure northern goshawk (Accipiter gentilis) home range sizes and characteristics in south central Idaho, I radio-tracked six breeding males throughout the breeding seasons of 2001 and 2002. Males were tracked from the time young were 5-10 d old until 20 d post-fledging. I collected 485 temporally independent locations, 428 of which were triangulated, and 57 of which were obtained visually. I acquired a mean of 54 (± 3.3) independent locations per bird. Average linear error associated with triangulated locations was 130 m. Median minimum convex polygon home range size was 588 ha for males that successfully fledged young, and 542 ha for unsuccessful males. Median 85% cluster core area size was 98 ha for successful males, and 70 ha unsuccessful males. Home ranges contained an average of 1% seedling (\u3c 2.5 cm dbh), 13% sapling/pole (2.6-12.9 cm dbh), 37% small tree (13-34 cm dbh) and 51% total forest cover and 49% shrubsteppe habitat. Core areas contained an average of 1% seedling, 11% sapling, 47% small tree, 57% total forest cover, and 48% shrubsteppe habitat. These home ranges are smaller than those reported for elsewhere in North America. This may be due to high densities of hunting areas, which include areas of forest-shrubsteppe interface, where goshawks perch on forest edges to hunt open-country prey. Home ranges of both successful and unsuccessful males increased significantly in size after the mean fledging date of successful males\u27 young. Home ranges of neighboring males overlapped. CHAPTER 2: NORTHERN GOSHAWK FORAGING HABIT AT SELECTION IN SOUTH CENTRAL IDAHO To assess northern goshawk (Accipiter gentilis) habitat selection at two scales in south central Idaho, I radio-tracked six breeding males throughout the breeding seasons of 2001 and 2002. Males were tracked from the time young were 5-10 d old until 20 d post-fledging. I collected 485 temporally independent locations, 428 of which were triangulated, and 57 of which were obtained visually. I acquired a mean of 54 (± 3.3) independent locations per bird. Average linear error associated with triangulated locations was 130 m. Habitat variables measured included: distance from used (obtained through radio telemetry) and available (randomly selected within home ranges) locations to the nearest seedling (\u3c 2.5 cm dbh) stand, sapling/pole (2.6-12.9 cm dbh) stand, small tree (13-34 cm dbh) stand, road/trail, and camp area. I used logistic regression to identify those features that may be important in predicting individual goshawk use of a perching site. Five out of six males selected perching sites closer to small tree habitat and camp areas than expected. Two males selected perching locations closer to roads/trails than expected, and two males selected higher or lower elevations than expected. I also examined habitat selection at the scale of home range placement within the study area using home-range sized sampling ellipses placed around 23 known historical nests, and 23 randomly selected locations within the study area. At this scale, goshawks selected for less sapling/pole habitat, and greater habitat diversity as measured by Shannon\u27s diversity index, similar to results from other studies. Selection for landscape features associated with human activity and fragmented forests poses new questions regarding the effects of human activity on breeding goshawks