Osprey

Hover, then plunge

The osprey is a fish-hawk, and its hunting move is a plunge. Its diet is almost entirely fish. It flies slowly over the water and pauses to hover when it spots a fish below. If the fish is close enough to the surface, the osprey drops feet-first and grasps its prey in its talons. Just before it hits the water, it swings its legs forward and bends its wings back. Then it lifts off with strong, almost horizontal wing beats, carrying the fish head-forward with its feet. The Bald Eagle sometimes chases an osprey and forces it to drop its catch.

Built for slippery prey

An osprey has relatively long legs for a raptor, which is a bird of prey, and long, sharp, curved claws. It also has dense oily plumage and efficient nasal valves that stop water entering its nostrils when it dives.

Grip gear An osprey has spiny footpads called spicules and a reversible outer toe to aid in gripping slippery fish.

Size, weight and lifespan

Audubon’s North American field guide gives an osprey’s length as 54 to 58 cm, with a wingspan of 1.5 to 1.8 m. Its weight is 1.4 to 2 kg. Female ospreys are 20% heavier than males on average, according to ADW, though not necessarily longer. Tropical and subtropical ospreys tend to be smaller than those that breed at higher latitudes. AnAge lists a maximum longevity of 32 years in the wild.

Nearly worldwide

The osprey is one of six landbird species known to breed in every biogeographical region of the world except Antarctica. Nests are usually on top of large trees, and also on utility poles and other structures. A pair uses the same nest year after year, repairing it and adding material before eggs can be laid. The male brings fish, and the female feeds them to the young. In North America, some ospreys are permanent residents in southern Florida, while the rest migrate, and migrants travel singly, not in flocks.

A 2015 genetic study of two mitochondrial genes found the osprey structured into four genetic groups in mostly separate regions: Indo-Australasia, Europe and Africa, the Americas, and north-east Asia.