A review and evaluation of factors limiting northern goshawk populations

Abstract

Northern Goshawk (Accipiter gentilis) populations are suspected of declining due to forest management treatments that alter the range of environmental conditions beneficial to their reproduction and survival. To develop effective goshawk conservation strategies, information on intrinsic and extrinsic factors that influence goshawk fitness is required. We reviewed the literature for information on factors that commonly limit avian populations, and were, therefore, potentially limiting goshawk populations. We evaluated the relative importance of these factors, and discussed how and at what scale these factors operate to constrain goshawk populations. Food availability and forest structure appeared to be the most ubiquitous factors limiting goshawks, but the degree to which these factors affected goshawks appeared to depend on interactions with other limiting factors such as weather, predation, competition, and disease, each of which operates at multiple spatial and temporal scales. Goshawks occur primarily in forests and woodlands, but the degree to which they are limited by forest composition and structure is difficult to determine because goshawks, at both the individual and population levels, use a wide variety of structural conditions while foraging. Much of the diversity in habitats used by hunting goshawks appears to result from their entry into the diverse habitats of their prey. Our review suggested that the availability of suitable nest sites influences goshawk site occupancy and reproduction, but that forest structural conditions beyond nest sites have a larger effect on goshawk reproduction and survival by affecting both the abundance and accessibility of their prey. This highlights the importance of conservation strategies that address a range of ecosystem needs by integrating the diverse habitat requirements of the goshawk prey community with the forest structural components of goshawk nest sites and foraging areas.

Citation

Reynolds, Richard T.; Wiens, J. David; Salafsky, Susan, R. 2006. A review and evaluation of factors limiting northern goshawk populations. Studies in Avian Biology. 31: 260-273.