A META-ANALYSIS OF THE INFLUENCE OF TIMBER HARVEST ON NORTHERN GOSHAWK REPRODUCTIVE OUTPUT
Sabrina Rodriguez1, Timothy Parker1, Patricia Kennedy2.
1Whitman College, Walla Walla, WA, 2Oregon State University, Corvallis, OR.
The northern goshawk (Accipiter gentilis) is a species of conservation concern, but despite decades of research, the sensitivity of reproduction to habitat quality remains uncertain. These relationships had yet to be systemically reviewed; therefore, we studied the effects of timber harvest on goshawk reproduction. To answer our question, we used a meta-analytic test which combines published statistical results into a single, stronger statistical value bounded by confidence intervals. We assembled all published studies that compared reproductive output in harvested and unharvested areas and compared reproductive success in relation to tree size near nests. A negative value for our standard effect size and an associated confidence interval that broadly encompassed zero (Zr = -0.0634 ; 95% CI = -0.3037 to 0.1769, N = 8 studies) indicated that goshawk reproductive output was not negatively affected by harvest or absence of older trees. While goshawks occupying territories near timber harvest do not suffer reduced reproduction, many goshawks may respond to timber harvest by abandoning nests, so we plan to conduct another meta-analysis determining the effects of harvest on site occupancy by goshawks.