This species of tropicbird usually forages alone. The white-tailed tropicbird "(Phaethon lepturus)" is a tropicbird. These predators have the potential to drive populations of the red-billed tropicbird into serious decline. Cats also threaten the red-billed tropicbird. The red-billed tropicbird is basal within the genus. The island is also home to an endemic subspecies of white-tailed tropicbird ("Phaethon lepturus europae"). The red-tailed tropicbird is generally silent while flying. The red-billed tropicbird itself has three subspecies recognized, including the nominate. Its red bill and more wholly white wings distinguish it from the adult white-tailed tropicbird. Birds breeding on Pitcairn include the fairy tern, common noddy and red-tailed tropicbird. Saba's shoreline is home to the Caribbean's largest breeding colony of Red-billed tropicbird ("Phaethon aethereus"). The red-tailed tropicbird sometimes catches flying fish in the air. Vagrant red-billed tropicbirds have been implicated in egg loss in red-tailed tropicbird nests in Hawaii. However, the red-billed tropicbird sometimes follows surface-feeding predators. The white-tailed tropicbird feeds mainly on flying fish, squid and crabs.