It Takes Guts (And More) to Eat Fruit: Lessons from Avian Nutritional Ecology
journal contributionposted on 01.10.2001, 00:00 by D. J. Levey, Carlos Martinez del Rio
Many studies in the last 20 years have examined the basis of fruit choice in birds. It is somewhat frustrating that results of those studies are often inconsistent. Different species and even different individuals of the same species can prefer different fruits (e.g. Johnson et al. 1985, Whelan and Willson 1994, Willson 1994, Young 1992). Although it is clear that birds’ preferences are not random (Moermond and Denslow 1985), it is equally clear that generalizations about what underlies their choices are premature even after two decades of research. We rarely understand why birds eat the particular fruits they do. Conversely, we understand even less about why birds do not eat many species of fruit they encounter frequently. In fact, the more one ponders the question, “Why don’t more birds eat more fruit?”, the more perplexing it becomes. After all. Fruits are “made to be eaten.” Unlike most other dietary items, they represent a mutualistic link – their consumption presumably benefits both the bird and the plant (Snow 1971). Fruits are comparatively easy to find, easy to capture, and often easy to digest. Why, then, do most species of birds rarely or never consume fruits? And, of those species that do consume fruit, why do they not consume more fruit and a larger suite of fruit species?