Comparison of Nest Defense Behaviors of Goshawks (Accipiter gentilis) from Finland and Montana

Abstract

As human impacts on wildlife have become a topic of increasing interest, studies have focused on issues such as overexploitation and habitat loss. However, little research has examined potential anthropogenic impacts on animal behavior. Understanding the degree to which human interaction may alter natural animal behavior has become increasingly important in developing effective conservation strategies. We examined two populations of northern goshawks (Accipiter gentilis) in Montana and Finland. Goshawks in Finland were not protected until the late 1980s, and prior to this protection were routinely shot, as it was believed that shooting goshawks would keep grouse populations high. In the United States, Goshawk were not managed as predator control. Though aggressive nest defense has been characterized throughout North America, goshawks in Finland do not show this same behavior. To quantify aggression, we presented nesting goshawks with an owl decoy, a human mannequin, and a live human and recorded their responses to each of the trial conditions. We evaluated the recordings for time of response, duration of response, whether or not an active stimulus was present to elicit the response (i.e., movement or sound), and the sex of the bird making the response. We used t-Test with unequal variance to compare mean number of responses and response duration. Our results suggested that goshawks in Montana exhibit more aggressive nest defense behaviors than those in Finland. While this could be due to some biotic or abiotic factor that we were not able to control for in a study on such a small scale, it is also possible that the results from this study suggest another underlying cause, such as an artificial selection pressure created by shooting goshawks.

Habitat Suitability Modeling and Ecological Forecasting of Northern Goshawk Nesting Habitat

“…Many of the studies that have examined nest stand and nest tree requirements for goshawks have focused on areas of wet forest that receive substantial annual precipitation (Hayward and Escaño 1989, Lilieholm et al 1993, Bull and Hohmann 1994, Squires and Ruggiero 1996, Bruggeman et al, 2011). The areas of the HLCNF used in this study identifying goshawk nesting habitat represent predominantly warm, dry forest with little annual precipitation (max ~330 mm;(DeBlander 2002, Wright et al, 2019). Although other studies of goshawk habitat on dry forest have been performed, this study will endeavor to identify possible changes to the forest via climate change (Beck et al, 2011,,.…”