Protecting Vegetables from Crows Using an Animated Crow-Killing Owl Model

Abstract

The American crow (Corvus brachyrhynchos) causes problems for both farmers and gardeners by feeding on many crops including melons, small and large fruit, tomatoes, corn, and other vegetables. Lethal control often is not a viable option, scarecrows are not effective deterrents (M. R. Conover, unpubl. data), and chemical repellents cannot be used on most fruit and vegetables. Consequently, there is no adequate solution to most crow problems. Predator models and other fear-provoking stimuli have often been used in an attempt to reduce bird damage to crops (Conover 1982), but birds usually habituate rapidly to them, limiting their effectiveness (Conover 1979). Birds apparently habituate to predator models because, unlike live predators, their spatial context does not change (Shalter 1978), they are inanimate (Conover 1979), and they never attack or kill other birds (Conover and Perito 1981). This last factor may be particularly important for crows because they mob a predator more vigorously when it has killed or is holding a crow (Barash 1976, Denson 1979). In this study, I tested whether an animated model of an owl grasping a crow model would protect small garden plots from crows more effectively than other commonly used models.