Northern Goshawk Occupancy and Breeding Surveys

This article was originally published in The Midden – Great Basin National Park: Vol. 16, No. 2, Winter 2016.

A northern goshawk nest in the park.

NPS Photo

By Julie Long, Biological Science Technician

Northern goshawks (Accipiter gentilis) are large diurnal raptors that can be found year-round at Great Basin National Park. Although this bird of prey is a Nevada resident, it has been listed as a sensitive species by Great Basin National Park, the Bureau of Land Management, U.S. Forest Service, and the Nevada National Heritage Program. In order to better understand their ecology, habitat use, and nest and fledgling success, we conducted northern goshawk surveys in late July and early August.

Surveys were implemented in collaboration with the Nevada Department of Wildlife (NDOW) using their northern goshawk occupancy and breeding survey protocol. Five sites were surveyed in the park: Mill Creek, South Fork Big Wash, Strawberry Creek, Can Young Canyon, and Pine Creek. A subset of these locations was last visited in 2011. Historic nest sites were located in riparian habitat in cottonwood, aspen, or aspen-mixed conifer forest. Surveys involved walking transects near previously documented northern goshawk nest locations. Call-broadcast sessions were performed every 150 meters if no goshawk activity was detected at the nest site. Data on dominant tree community, cloud cover, temperature, and DBH (diameter of breast height of the nest tree) along with nest condition were recorded.

A northern goshawk seen in the park this summer.

NPS Photo

We found occupied territories in Can Young Canyon and South Fork Big Wash. In South Fork Big Wash, two fledged juveniles were observed with some down feathers still present. In Can Young Canyon one juvenile with buffy brown streaks was heard and then later observed at a historical goshawk nest site in a dead quaking aspen. At other historical sites, intact nests were identified without any activity. Three inactive nests were documented in aspens in Pine Creek. Observations of intact nests without any goshawks present may be due to the timing of survey efforts. Fledged juveniles may have already left the nest, or the nests may have been abandoned.

Revisiting nest sites is important to document preferred nesting habitat, changes in occupancy, nesting success, and timing of nesting and fledging. These surveys give the park information on site occupancy over time and breeding behaviors. Having this knowledge will not only provide sensitive species information to management but allow them to protect habitat that goshawks favor for nesting.