Effects of Social Facilitation and Observational Learning on Feeding Behavior of the Red-Winged Blackbird (Agelaius phoeniceus)

Abstract

-In the presence of food-deprived and therefore rapidly feeding Red-winged Blackbirds (Agelaius phoeniceus), pairs of nondeprived conspecifics increased their own food consumption and spillage. The effect of social facilitation appeared amplified when both pairs of birds were food-deprived. Blackbirds also showed clear differential preferences for novel foods based on observations of male conspecifics consuming and spilling novel food. Social facilitation of feeding and observational learning of differential food preferences for novel foods may help to explain the Red-winged Blackbird's tendency to locate and exploit (i.e. damage) crops during short periods when the crops are especially vulnerable. Received 30 January 1981, accepted 21 April 1981. SOCIALLY facilitated behavior such as flocking may protect birds from predators (Conner et al. 1975, Clayton 1979, Lazarus 1979) and contribute to reproductive synchrony (Roell 1978). Social facilitation may also lead to a more complete exploitation of food resources by birds through more rapid selection of new foods (Davies 1976, Traemer and Kemp 1979) or through increased food consumption (Rubenstein et al. 1977, Feare and Inglis 1979). Consumption is influenced by the feeding rates of neighboring birds in a flock, regardless of their sex, or, sometimes, their species (Fairchild et al. 1977). In addition, consumption is discriminative for most species, i.e. individuals forage selelctively and tend to choose foods that other birds in the flock are choosing (e.g. Murton 1971, Williamson and Grey 1975). Social facilitation of food selection among members of a flock may have deleterious agricultural consequences. For example, foraging based on observational learning may encourage the selective crop damage that is often produced by gregarious pests, such as Red-winged Blackbirds (Agelaius phoeniceus). Here, we report two experiments that demonstrate that: (1) Red-winged Blackbirds will increase their feeding activity in the presence of feeding conspecifics; and (2) Red-winged Blackbirds differentially select some foods as a result of observing the behaviors of other individuals. EXPERIMENT 1, SOCIAL FACILITATION OF FEEDING