The Caribbean Islands compose one of the most diverse ecosystems within the United States. The U.S. Caribbean is in the eastern extreme of the Caribbean archipelago half way between the Florida peninsula and Venezuela. Puerto Rico and the U.S. Virgin Islands provide great opportunities to protect and restore tropical forests ecosystems, neotropical migratory bird wintering grounds, and habitat for more than 78 federally listed species.

In just a few miles an observer can travel from a tropical rain forest to the sub-tropical dry forest ecosystem. Coral reefs, mangrove swamps, gorgeous rivers and streams, forested and herbaceous wetlands are within the most prominent ecosystems in the Caribbean Islands.

Many birds find their way to the refuge while migrating between North and South America including the Praire Warbler; Northern Parula and Cape May Warbler. These birds use the refuge during the cooler months, while resident species including the Puerto Rican Tody, Adelaide's Warbler; Caribbean Elaenia, Troupial and the endangered Yellow-shouldered Blackbird are here year round.