American robins, Turdus migratorius, reportedly damage maturing grapes throughout California and the Pacific states. They become pests in vineyards when their migration patterns bring them into areas where grapes are maturing.|
About 8 to 10 inches tall, the American robin has a dark brown head and tail and a gray-brown back. Most distinctive are its brick red breast feathers and yellow, pointed bill.
The American robin is migratory, breeding in the northern portions of its range in spring and moving south during winter. Breeding in spring throughout California, robins produce two or three young in shallow nests of sticks and mud built in trees. Often seen foraging in turf areas, they feed primarily on insects and worms. Their other major foods are wild and cultivated berries, including grapes.
American robins are considered migratory non-game birds under federal regulations. A depredation permit issued by the U.S. Fish and Wildlife Service is required when lethal control measures are used.
Like the starling, the robin plucks the entire berry from a bunch of grapes, substantial damage can result to vineyards when migratory flocks of robins move in near harvest time.
American robins are relatively easy to spot and identify. The numbers of migrants in California vary greatly from year to year, so vineyards where damage occurred in previous years may not be damaged subsequently. Look for robins feeding in and around vineyards in early morning or late afternoon. Look for birds when grapes near maturity.