ABSTRACT
Foraging blackbird flocks have great mobility as they search for food that is plentiful, is easily accessed, and has a high nutritional value. Ripening corn, rice, and sunflower fit those criteria, as does seeded rice. The birds will move from field to field to find the ideal combination of energy spent to discover food versus the energy value of the food (Pyke et al. 1977). An extraordinary effort is often needed to actively move the birds from a foraging location with a high positive value (e.g., close to roost and early ripening sunflower) versus a location with a low value (e.g., far from roost and mature corn). Indeed, Handegard (1988) relayed that despite the intense use of low-flying aircraft and live shot-shell ammunition, field specialists were not able to move blackbirds from sunflower fields located near cattail-dominated (Typha spp.) wetland roosts. In this case, birds were also undergoing their annual feather molt, which hampered flight and increased the energetic cost of moving to a new foraging site (Linz et al. 1983).
