Importance of color for methiocarb-induced food aversions in red-winged blackbirds [Crop pests, Agelaius phoeniceus]

Red-winged blackbirds (Agelaius phoeniceus) were intubated with methiocarb, lithium chloride (experimental groups), or propylene glycol (control groups) before or after eating colored oats. Only birds given toxic gavage after eating colored oats showed food-aversion learning. Blackbirds intubated with methiocarb after eating familiar bird chow paired with colored rectangles avoided chow only when it was paired with the appropriate color cue. Blackbirds intubated with methiocarb subsequently avoided, in decreasing order, (1) food and color paired with intubation, or color paired with intubation but unpaired food; (2) food paired with intubation but unpaired color; and (3) unpaired food and color. Birds intubated with propylene glycol showed no such differential behavior. Use of distinctive visual cues may improve the efficacy of methiocarb as a bird repellent, visual cues may be effective without actually coloring the crop (e.g., colored flags), and Batesian mimicry could serve as the conceptual basis for studies of methiocarb as a bird repellent.