The osprey (Pandion haliaetus), sometimes known as the sea hawk, fish eagle, river hawk or fish hawk, is a diurnal, fish-eating bird of prey. Most are migratory that breed in the north and migrate south for the winter. Though fish are by far the most important part of the diet, ospreys have been recorded catching a wide variety of other prey, including birds, reptiles and even crustaceans. Ospreys are one of the world's most widely distributed birds, and is found in temperate and tropical regions of all continents except Antarctica. The Osprey is particularly well adapted for catching fish. They have reversible outer toes, sharp spicules on the underside of the toes, closable nostrils to keep out water during dives, and backwards-facing scales on the talons which act as barbs to help hold its catch. In fact, the Osprey and Owls are the only raptors whose outer toe is reversible, allowing them to grasp their prey with two toes in front and two behind. In the late 19th and early 20th centuries, the main threats to Osprey populations were egg collectors and the hunting of adult birds.