Response of Birds to Raptor Models

INTRODUCTION Today, more than ever, there is an increasing need for non-lethal methods to effectively control crop depredation by birds. One such method, involving the use of fear-provoking stimuli, has been used since ancient times but often with little success. If fear-provoking stimuli are to be improved, we must identify those features that are most effective and incorporate these into scare devices. Models of raptors are promising fear-provoking stimuli (Rowe 1971, Brown 1974, Messersmith 1975, Blokpoel 1976). Unfortunately, birds usually habituate to these models rather quickly. More efficient models have not been devised, in part because of the lack of experimental studies on predator models and other fear-provoking stimuli. Therefore, I have examined the effectiveness of three predator models by quantifying how birds respond when exposed to them for various lengths of time. Raptor Models Three models were tested. Two were museum mounts of a sharp-shinned hawk (Accipiter striatus) and a goshawk (A. gentilis), which were loaned to me by the Peabody Museum of Yale University. The third model was a kite-hawk which was a clear plastic kite on which was printed a colored drawing of an eagle with its wings outstretched in flight. To keep the kite aloft in little or no wind, it was suspended from a helium balloon. The helium ballon was 40-60 meters above the ground, and the kite-hawk was midway between the balloon and ground. The goshawk and sharp-shinned hawk models were mounted as perching hawks and were placed 1.25 to 2 m above the ground. Feeder Station Experiments The first series of experiments tested the predator models at feeding stations. For these tests, five feeders were established in the vicinity of New Haven, Connecticut. Three located at the Lockwood Farm in Mt. Carmel, Connecticut, were placed 200 to 400 m apart, out of sight of each other. Another feeder was located in Woodbridge about 15 km from the Mount Carmel feeders, and the fifth feeder was placed in Orange, Connecticut approximately 7 km from the Woodbridge feeder and 20 km from the others. All feeders were in open fields and were near community garden plots or small fields of cultivated row crops. Each feeder consisted of a 1 m 2 wooden platform with 5 cm side boards, and was positioned 1.0 to 1.25 m above the ground. Each feeder was baited daily, or on alternate days, with 400 g of cracked corn and 400 …