| DeStefano, Daw, Dismone, Meslow | Stephen, Sonya K., Steven M., E. Charles | Density and productivity of northern goshawks: Implications for monitoring and management. | 1994 | In The northern goshawk: Ecology and Management. W. M. Block, M. L. Morrison, and M. H. Reiser (eds.). Proc. Symp. Cooper Ornith. Soc., 14-15 April 1993, Sacramento, CA. Studies in Avian Biology. 16: 32-40 |
Abstract
We studied Northern Goshawks (Accipiter gentilis) breeding populations on five study areas on the Fremont, Malheur, and Wallowa-Whitman National Forests in eastern Oregon during 1992 and 1993. We found 50 active territories, with average densities of .07 active territories per 100 ha (SE=.15, N=3 study sites) in 1992 and .06 (SE=.15, N=5 sites) in 1993. However, densities were variable both between years and among areas within each year, and no consistent patterns were seen based on forest cover type. Productivity (number of young fledged per nest) was also variable between years and among study sites within the same year. Current USDA Forest Service management for goshawks emphasizes reducing tree harvest around specific nest sites or post-fledging family areas (PFAs). Our data, however, show that numbers of nesting goshawks are variable among years, and not all breeding sites will be discovered in a single year of survey. We recommend multiple-year surveys for nesting birds and habitat management on a landscape rather than "per nest" basis.Management Implications (pg. 90)
Current USDA Forest Service management for goshawks in Region 6 (Oregon and Washington) call for establishing protected zones around some nest sites (nest sites in areas under current timber harvest contracts are often exempt), where no or reduced timber harvest would take place. These zones are of variable size from 2-12 ha (5-30 acres). Recently managers have been directed to protect larger areas around goshawk nest sites corresponding to the post-fledging family area (PFA).
These approaches necessitate finding "active" goshawk breeding sites, and promotes management on a "per nest" basis. Data from this study suggest that not all nest sites are active in all years, and searching for goshawk nests in a single season in preparation for potential timber sales could easily overlook territories.
Due to the variability in nest sites, the authors recommend an absolute minimum of two years of surveys and preferably three to four years in an area before allowing timber harvest.(pg 91) Management plans suggested by Reynolds et. al. (1992) consider other forest-dependent species and promote management at a more holistic level.