Rainfall correlates of bird population fluctuations in a Puerto Rican dry forest: A 10-year study

Abstract

Long-term studies on the population dynamics of Neotropical bird communities have been primarily limited to Panama (see Karr et al. [1982] for a mainland site and Willis [1974] for Barro Colorado Island). An earlier paper (Faaborg 1 982a) contained the first long-term population measurements from a West Indian island, specifically a seasonally-dry forest site in southwest Puerto Rico. This 5-year study apparently spanned a population peak followed by drought conditions and a severe population decline. The effects of drought on total populations, membership in different foraging guilds, and winter resident densities were discussed. We have continued these studies and here report on 9 years of banding and population monitoring activities in a single location. This allows us to expand our previous observations on relationships between rainfall patterns and population traits of guilds and species and expose the data to statistical analyses. We also document the attempted invasion of a new species (Elaenia martinica) into the Guanica Forest bird community. The possible meaning of these observations in terms of island equilibrium theory (MacArthur and Wilson 1967), long-term climatic patterns (Pregill and Olson 1981), and community structure studies (Faaborg 1982b) is discussed.