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

Marilyn Wright,Risto Tornberg,Nate Bickford,Dustin Ranglack

doi:10.3390/ani9030096

Abstract

Simple SummaryUnderstanding 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 shot as a management strategy. 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 used statistics to compare the two populations. 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.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.

Highlights

Human impacts on wildlife have become a topic of increased interest in the last few decades, but, while many studies focus on direct impacts such as overexploitation and loss of habitat, there are fewer studies focusing on the impacts humans have on animal behaviors [1]
Throughout this study, the Goshawk population sample in Montana was consistently more aggressive than the population sample studied in Finland
This was evident in comparisons of raw data including number of responses, number of passes, and duration of responses, all of which were greater for the goshawks in Montana

Summary

Introduction

Human impacts on wildlife have become a topic of increased interest in the last few decades, but, while many studies focus on direct impacts such as overexploitation and loss of habitat, there are fewer studies focusing on the impacts humans have on animal behaviors [1]. Landfills and garbage dumps are regularly visited by animals that have become conditioned to feeding on human waste as opposed to food available in their natural environment [2,3] Predators such as coyotes (Canis latrans) and mountain lions (Puma concolor) inhabit urban areas [4,5]. Migratory animals such as birds and elephants will commonly choose routes and stop-over sites with the least amount of human disturbance [1,6,7], and Killer whales (Orcinus orca) and Amur tigers (Panthera tigris altaica) significantly reduce time spent foraging or consuming a kill to avoid human contact [1,8,9,10]. While some of these changes may be beneficial in some regards, they may have the potential to affect the survival and reproduction potential of individuals, affecting population size [1]

Methods

Results

Conclusion