Osprey

The osprey (Pandion haliaetus) is found on every continent except Antarctica, but it is much less common in some parts of the world than others, especially where its habitats have come under threat or it has been regarded as a pest. However, it is a bird that is spectacular to watch, and breeding programs have been well supported, and remarkably successful, in a number of locations.

Appearance

It is a moderate sized raptor (bird of prey) that feeds on fish. The body length is about 20-23 inches (51-19 cm) (the females are larger than the males) and it has a wing span of between four-and-a-half and six feet. The head is protruding, with a small crest, and the tail is short. The feet are specially adapted for catching slippery fish, with reversible front toes and thorn-like protuberances (known as spicules).

The adult birds are mostly brown on top but white underneath. The head is mostly white, but with black or dark brown eye-bands.

Behaviour

In flight, the osprey is powerful, with shallow, flexible beats of its wings. It soars and glides with its wings bent like a large gull. Its courtship flight consists of plunges, upward swoops, and pauses with rapidly beating wings.

Watching the osprey hunt is particularly rewarding. It flaps and glides at about 50 feet above the water surface, hovering at intervals with its legs dangling, then it dives and extends its feet just as it hits the water. Sometimes it goes right under the surface, and birds have been known to drown if the fish puts up a fight. The fish is held in the talons and carried head first. After feeding, the osprey often trails its feet in the water to clean them.

Ospreys perch on bare trees, posts and rocks, near lakes, large rivers and sea coasts.

Breeding

Ospreys nest typically in dead branches at the top of tall conifers, but have been known to choose electricity pylons or cliff-top sites. The nest is a large, untidy affair that is visible from a large distance. In Scotland, the ospreys migrate from West Africa, arriving in late March or April, with the male appearing first to start building or repairing the nest. Pairs mate for life and return to the same nest site every year. However, observers have reported osprey “divorces” and even female birds “two-timing” with more than one male. It has been known for a male osprey to eject eggs from a nest when he suspected that they were not “his”.

Three eggs are the usual clutch, laid at intervals of a few days, and they take about 37 days to incubate. It is rare for all three chicks to survive, and it has been known for the weakest chick to be eaten by one of the others, or to be pushed out of the nest. Fledging takes about seven or eight weeks.

Conservation

The story of ospreys in the United Kingdom has been a tortuous one. For about 50 years, up until the late 1950s, there were no ospreys anywhere in the country. They had been the victims of egg collectors and deliberate attempts to wipe them out, prompted by fears that they were a threat to fish stocks. However, they have made a considerable comeback in Scotland, with more than 130 pairs now nesting. They are a protected species, and at some nesting sites volunteers guard the nests throughout the breeding season.

Efforts have also been made to encourage ospreys in England and the first English osprey chicks were hatched in 2001 after an absence of 150 years.

In North America, the Chesapeake Bay area of Maryland is especially noted for its osprey population, with the birds migrating from the Caribbean and Central and South America. As in Scotland, the population has recovered after a lean period for much of the 20^th century. The use of DDT on farmland had led to osprey eggs having thin, easily broken shells, and the banning of DDT has been a major reason behind the recovery of osprey numbers, as has the provision of artificial nesting sites.

Ospreys are now regarded as being a welcome part of the bird population, although there are still threats to their survival in many places. They are a favourite of bird watchers and naturalists, and their future seems assured in all parts of the world where they are given sufficient protection.

© John Welford