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On the Evolutionary Advantages and Disadvantages of Fruit Eating in Tropical Birds

1973; University of Chicago Press; Volume: 107; Issue: 953 Linguagem: Inglês

10.1086/282813

1537-5323

Eugene S. Morton,

Ecology and Vegetation Dynamics Studies

Positive and negative sources of selection on fruit-eating by birds are discussed. It is hypothesized that fruit is rarely favored as the complete diet for small nestling birds because it results in slower growth rates than those allowed by animal food. Nest predation pressure is greater in totally frugivorous birds and counteracts the advantages of the abundant and easily accessible food supply afforded by fruit. The evolutionary result of total frugivory is discussed, relating population size, rarity of nest sites, and clutch size to the rarity of totally frugivorous species. Frugivory in adult birds is discussed in relation to habitat, social behavior, and interspecific competition. It is hypothesized that total frugivory in adult birds is opposed by selection from occasional periods of low fruit abundance, when the ability to obtain animal food reaches limiting conditions. An evolutionary and ecological dichotomy between humid tropical-zone and temperate-zone birds is discussed. This dichotomy is due to the use of fruit during the breeding season by adult tropical birds, which allows them to use more time searching for animal food for nestlings. This results in a time-energy budget for breeding tropical birds that is not available for most breeding temperate-zone species. It is hypothesized that temperate-zone species would "choose," evolutionarily; animal food over fruit during the breeding season and that this has resulted in negative selection pressure on plants to produce fruit during the temperate-zone avian breeding season.