POPULATION DECLINES OF THE PUERTO-RICAN VIREO IN GUANICA FOREST

Abundance of the Puerto Rican Vireo (Vireo latimeri) in Guanica Forest , Puerto Rico, has declined gradually over the period 1973-1996 as det ermined by constant effort mist netting. Concurrent studies of breedin g vireos show low nesting success, primarily due to parasitism by Shin y Cowbirds (Molothrus bonariensis). This decline may reflect the rathe r recent entry of the cowbird into Guanica Forest during the breeding season, as other factors (vegetation change, rainfall) do not seem to explain the decline, As a single-island endemic, it is important that the cause of this decline be determined so that recovery efforts can b egin while the species is still moderately abundant.