Seed Color Avoidance by Captive Red-Winged Blackbirds and Boat-Tailed Grackles

Abstract

Offensive visual stimuli represent a potentially important component of avian crop damage reduc- tion strategies. Color perception by diurnal birds is highly developed, but the responses of the red-winged blackbird (Agelaius phoeniceus) to different-colored food have never been investigated. Red-winged blackbirds and boat-tailed grackles (Quiscalus major) cause substantial damage to newly seeded rice in the southern United States, and the examination of color avoidance by these species should contribute to the development of nonlethal methods to reduce depredations. We used rice seed of various colors to conduct a series of feeding trials with captive blackbirds and grackles. Despite variation among individuals and groups of test birds, blue was the least preferred color overall. Differences among species and among background color might affect responses of birds to a given seed color, but, in general, we suggest that blue should be incorporated into strategies for discouraging unwanted feeding by granivorous birds. In particular, further development of visual deterrents should exploit the ability of blackbirds and other species to detect wavelengths in the near ultraviolet. JOURNAL OF WILDLIFE MANAGEMENT 63(3):1003-1008