Environmental variability and long-term population dynamics of the Oilbird (Steatornis caripensis) in Trinidad

The Oilbird (Steatornis caripensis) is an important seed disperser in Neotropical forests whose population dynamics remain poorly understood. We evaluated long-term patterns of abundance and breeding activity in the Dunston Cave colony, Trinidad, and examined their relationships with vegetation productivity and rainfall. Monthly counts of adults and chicks collected between 2004 and 2015 were analyzed in relation to Enhanced Vegetation Index (EVI) data derived from MODIS imagery and local precipitation records. Seed remains collected in October 2015 were also compared with historical dietary data from 1957–1960. Oilbird abundance and vegetation productivity varied significantly over the study period. Diet composition differed from historical records, although palms remained the dominant food resource. Cross-correlation analyses revealed significant associations between colony dynamics, vegetation productivity, and rainfall. Adult and chick abundance peaked during the dry season, when EVI values were comparatively low, whereas rainfall was positively associated with adult abundance after a temporal lag. Breeding activity was concentrated between March and May, with peak chick abundance occurring in April. Our results indicate that seasonal environmental variation is associated with long-term patterns of Oilbird abundance and reproduction. Integrating satellite-derived vegetation indices with ecological monitoring offers a useful approach for assessing environmental influences on tropical frugivorous birds.