One of 6 birds with a worldwide distribution, these hawks are found on every continent except Antarctica. Ospreys are second only to the peregrine falcon in terms of distribution. Ospreys migrate in winter with migration routes being from the US to South/Central America, while those in the UK typically migrate to West Africa.
This hawk is the only raptor with an almost insatiable appetite for fish which constitute 99 percent of its diet. It has on average, a success rate of about 70 percent of strikes retrieving a fish. This raptor is such a specialist that it has physical characteristics that support its role. It has nostrils that can be closed during the dive as well as an outer toe that angles back to better grip the fish.
Ospreys live for 20 to 25 years and during that time can cover a respectable distance. A bird breeding in the US but wintering in the Amazon basin would cover about 5,000 miles (8,000 km) each way, assuming the bird lives the minimum 20 years. A simple calculation indicates 200,000 miles (321,000 km) migrating during its life!
Breeding pairs do not migrate together but will rejoin for breeding purposes when they return to the North. Birds can be found in Sub Sahara Africa but they do not breed there. Birds return to the Northern Hemisphere to breed.
The birds build a nest of sticks on a high outcrop or in a tree and this nest is called an eyrie. If a pair are unsuccessful in breeding in a particular year they will often build a new nest referred to in Scotland as a frustration eyrie.
This nest is normally used the following year and a new nest takes about 2 to 3 weeks to complete by both birds.
They normally lay three eggs at between 1 and 3 day intervals. Incubation takes 37 days. The female does most of the nurturing and protecting the young with the male doing the fishing. When the chicks are older the female helps with the fishing.
The young fledge at about 53 days and the parents continue feeding them while they stay close to the nest, for about 2 more months. Juvenile birds will reach maturity at 3 years but many die before that.
Ospreys have binocular vision which is great for judging distances, they fish on the water surface often fishing in the sea even when the nest is near a fresh water source.
Raptor vision is sometimes claimed to be 3.5 to 8 times better than ours but there is no definitive proof in this regard. What we do know is, an ospreys pupil is the same size as a humans pupil but their eyes have far more photo receptors packed into their retinas. Their eyes are more tube shaped meaning that they have a greater depth of field than we do. The downside is they don’t have the ability to almost instantly scan a wide area as we can but they are far better at zooming in on their prey.
Our osprey locks its talons into the fish to catch it and has pointed scales on its feet to help get a grip on the fish!