Osprey, Pandion haliaetus, sometimes known as the sea hawk or fish eagle, photographed at Quintana Neotropical Bird Sanctuary, Brazoria County, Texas, USA.
Image: Joseph Kennedy, 29 September 2010 [Would you like a look through a 'scope?]
Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece
1/640s f/8.0 at 1000.0mm iso400.
Questions: This daily mystery bird has a nearly cosmopolitan distribution, being found on every continent except Antarctica. Its feet are especially distinct, being specialised for its particular lifestyle. In addition to identifying this mystery bird, can you tell me what aspect of this species lifestyle has had such a profound effect upon the evolution of its feet, and (more challenging) can you tell me what is so special about its feet?
Response: The osprey, Pandion haliaetus, whose diet is limited to fish, can be found anywhere in the world where there is a reasonably large body of water, except Antarctica. Interestingly, fossils have even been found on the island of Tonga, where it was probably exterminated by arriving humans. This discovery has fuelled speculation that the osprey's range included many (most? all?) of the islands of the Pacific Ocean.
Osprey feet are particularly interesting. Unlike other raptors, all of its toes are the same length, its legs (tarsi) are reticulate (scaly), and its talons are round instead of having a groove running along their length. Osprey feet are also special because the outer toe is reversible (the same is true for owls), so they have three toes pointing forward, one back, when perching, but when grabbing a slippery fish, they will hold it with two toes pointing forward, two back. They also have scales on their feet that point "backwards", providing a non-slip surface that prevents struggling fish from slipping from their grasp.
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