Freeze-frame fruit selection by birds

The choice of fruits by an avian frugivore is affected by choices it makes at multiple hierarchical levels (e.g., species of fruit, individual tree, individual fruit). Factors that influence those choices vary among levels in the hierarchy and include characteristics of the environment, the tree, and the fruit itself. Feeding experiments with wild-caught birds were conducted at El Tirol, Departamento de Itapua, Paraguay to test whether birds were selecting among individual fruits based on fruit size. Feeding on larger fruits, which have proportionally more pulp, is generally more efficient than feeding on small fruits. In trials (n = 56) with seven species of birds in four families, birds selected larger fruits 86% of the time. However, in only six instances were size differences significant, which is likely a reflection of small sample sizes.