Competition between West Indian anoles and birds
Wright (1981) noted an inverse correlation between anole and insectivorous bird biomass in sclerophyll scrub habitats on seven West Indian islands. Anole biomass decreased and insectivorous bird biomass increased with increasing island size. He proposed the following explanation for this pattern: Anoles and insectivorous birds compete directly for arthropod prey, and anoles experience ecological release upon the extinction of an avian competitor. Bird populations are in greater danger of extinction on small rather than large islands in the West Indies, while anole populations seldom become extinct. Hence, anoles should experience ecological release and the resulting increase in abundance more often on small islands, while avian competitors of anoles should be relatively more abundant on large islands. Wright further states that in the process of expanding population size and taking a greater proportion of available anthropod prey after the extinction of an avian competitor, anoles may inhibit recolonization by insectivorous birds on small islands in the West Indes. Here we taken exception to Wright's argument for the following reasons: (1) An alternative hypothesis, that differences in predation account for the observed pattern, is at least as likely as the extinction-mediated competition hypothesis. Wright's superficial treatment of predation ignores the substantial and well-documented impact of introduced mammals and other predators on both lizards and birds. (2) Evidence of significant dietary overlap between birds and anoles is weak, at best. (3) Patterns observed in sclerophyll scrub cannot be generalized to other island habitats.
- Research Organization:
- Univ. of Puerto Rico, San Juan
- OSTI ID:
- 6043651
- Journal Information:
- Am. Nat.; (United States), Journal Name: Am. Nat.; (United States) Vol. 121:1; ISSN AMNTA
- Country of Publication:
- United States
- Language:
- English
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