Responses of captive blackbirds to a new insecticidal seed treatment

Development of new repellent chemicals specifically to control crop damage by birds may be cost-prohibitive. Instead, the use of compounds developed for other pest control needs may be more practical. Thus, we conducted 2-cup feeding trials with singly caged red-winged blackbirds (Agelaius phoeniceus) and brown-headed cowbirds (Molothrus ater) to test the repellency of a new seed treatment insecticide, imidacloprid (proposed common name for Miles Incorporated NTN33893). Both redwings and cowbirds were strongly deterred (P < 0.05) from feeding on rice seed treated with imidacloprid at 620 and 1,870 ppm. When applied to wheat seed, imidacloprid effectively reduced (P < 0.05) consumption by redwings at rates as low as 165 ppm. We noted treatment-related effects such as ataxia and retching in some birds exposed to the highest treatment levels, but such effects were transitory. Videotapes indicated that imidacloprid was not a sensory repellent or irritant to birds. We conclude that avoidance of imidacloprid-treated food is a learned response mediated by postingestional distress. Although developed and envisioned as a broad spectrum, systemic insecticide, imidacloprid also appears to have promise as a bird repellent seed treatment.