In ornithology:

• Red-tailed Black Cockatoo, large cockatoo native to Australia
• Red-tailed Comet, medium-sized hummingbird found in the Andes of South America
• Red-tailed Hawk, large Buteo which breeds from western Alaska and northern Canada to Panama and the West Indies
• Red-tailed Tropicbird, seabird that nests across the Indian and Pacific Oceans

In other fields:

• Red-tailed black shark, species of freshwater fish in the carp family, Cyprinidae
• Red-tailed Boa, the second largest member of the family Boidae after the anaconda
• Red-tailed Sportive Lemur, nocturnal species feeding largely on leaves