Determination of the factors that rule the preference of birds for certain fruits is fundamental to the understanding of the co-evolution of plants and their dispersers (Alves-Costa & Lopes 2001). Plants might compete for dispersers, and the response of dispersers will differ according to the variety of fruits available in nature (Denslow & Moermond 1982, Herrera 1981). Seed dispersal by birds is directly related to certain features of fruit, including colour, size, shape, abundance, nutritional value, habitat and distance between plants that are fruiting (Alves-Costa & Lopes 2001, Galetti et al. 2003, Levey et al. 1994, Murray et al. 1993). To understand how birds integrate these features in terms of fruit choice is a complex and widely misunderstood problem (Levey et al. 1994).
