Northern goshawk habitat on the Kaibab National Forest in Arizona: factors affecting nest locations and territory quality

Abstract

The northern goshawk has been at the center of controversy over its habitat management in the southwestern United States for the past decade. Fire suppression, grazing, and especially logging in coniferous forests are thought to be responsible for altering the composition and structure of forest habitat used by goshawks and their prey, thereby resulting in population declines. Conservation efforts for goshawks have focused on restoring forest structure to pre-settlement conditions using a combination of mechanical (logging) and natural (fire) methods. Many studies of goshawk habitat requirements have focused on the hawks' habitat use, food habits, movements, distribution, demographics, and diets; however, no studies have attempted to use spatially explicit models to describe the spatial dynamics between goshawks and their environment, which is of critical importance to their survival. In this study, I develop a dynamic spatial simulation model to assess the spatial relationships between goshawk habitat composition and structure and the location of active nests (i.e., in which eggs were laid), and I examine the relationships between the amount and arrangement of habitat elements surrounding nests in high quality territories. Prior to assessing these relationships, I developed models of vegetation composition and structure for the study area and assess the models' performance. The location of goshawk nests and assessments of territory quality estimated from reproductive performance are based on a population of banded goshawks on 101 territories studied from 1991 through 2000 on the Kaibab National Forest (North Kaibab Ranger District) northern Arizona.