Effects of bill pigmentation and UV reflectance during territory establishment in blackbirds

Does bill pigmentation influence territorial interactions of blackbirds ? Males YES: Resident males spent more time >10m from models with brown bills than from models with yellow or orange bills and a greater proportion of time >2m from orange billed models than from yellow-billed models (Fig. 4). Resident males also displayed more quickly (but not more aggressively) to models presented with orange bills than to models presented with yellow bills.