Seed and Color Preferences of Wild Carrion Crows From Cafeteria Experiments

Abstract

Birds can cause significant damage to agricultural fields, notably in Europe, where corvid species like carrion crows (Corvus corone) and rooks (Corvus frugilegus) target spring crops, posing challenges for conservation and wildlife management. Among targeted crops, sunflower and maize suffer the highest levels of damage from corvids' foraging. While both lethal and non-lethal strategies are employed to mitigate bird damage, their effectiveness is limited and context-dependent. Consequently, there is growing interest in identifying natural bird repellents. To improve our understanding of corvid food selection and explore potential non-lethal management strategies, we conducted (1) cafeteria trials with five common seed types (maize, sunflower, soy, pea, and wheat) and (2) two-choice color tests with maize seeds in four colors (blue, green, orange, and red) on an urban population of carrion crows accustomed to human presence. Results indicated a marked preference for sunflower and wheat, while soy and pea were largely avoided, and maize was moderately consumed. The crows also demonstrated a preference for green-colored maize over blue, orange, red, and natural maize seeds. These findings suggest that strategic planting of preferred crops like wheat alongside sunflower or maize may help mitigate damage. Further, incorporating colors into repellent seed coatings could reinforce the aversive learning process in birds, although color may play a less significant role in food selection when seeds are sown.