The lesser frigatebird (Fregata ariel) and great frigatebird (Fregata minor) are both found in large numbers on the island.

There are an estimated 3,000 breeding pairs of lesser frigatebirds in the park and a smaller number of great frigatebirds.

Lesser frigatebirds are mostly black and grow to about 75 cm in length. Females have a white breast and belly, while males have a large red gular sac on their neck, which they inflate to attract a mate.

The great frigatebird is similar in appearance, but significantly larger, growing up to 105 cm with a wingspan of more than two metres.

Both species nest in trees and feed on fish caught at the surface of the ocean.