The Implications of Forest Edge on Northern Goshawk Nest Location in the Bridger-Teton National Forest

Abstract

In the past few decades, scientists have become concerned about declining Northern Goshawk (Accipiter gentilis) numbers and have subsequently focused on identifying and defining characteristics of their nesting habitat Northern Goshawks living in the U.S. often choose to nest in old growth trees contained within mature forests, but questions remain about whether or not they select sites near or far from forest edges. Previous studies of Northern Goshawk selection for nest sites containing forest edge are inconclusive. To better understand Northern Goshawk nesting preferences with regard to forest edge in the Bridger-Teton National Forest, I analyzed 12 Northern Goshawk nests that were found during a study conducted in 2012 and 2013 by the Rocky Mountain Bird Observatory, as well as nests found by the United States Forest Service (USFS). To determine the effects of forest edge on Northern Goshawk nest site, I used GIS software to measure three distances—from nest to closest forest edge, nest to closest natural forest edge, and nest to closest disturbed forest edge—and compared these measures to randomly determined control points. Disturbed forest edges were categorized as highly or lightly disturbed. I found that Northern Goshawks nested further from natural forest edges than random points (tip = -2.04, p = 0.03729) and found no significant difference between the highly disturbed forest edges and lightly disturbed forest edges (ts = -0.1977, p = 0.8552). The data concludes that Northern Goshawks nested closer to disturbed edges than would be expected due to chance. Results indicate that goshawks avoid natural forest edge when choosing a nest site, but may not always avoid disturbed forest edges, such as roads. This information has implications for the USFS management decisions in the Bridger-Teton National Forest for proper Northern Goshawk conservation.