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Hi all,
Mary Farrant asked a good question about how Ospreys replace their feathers. This is a really fascinating topic, and so here is a crash course in feathers and molt.
Feathers Part 1
Adult Ospreys replace all their feathers once a year, but they do it in a very interesting way. Young Ospreys tend to take a bit longer than a year to replace their feathers. Molting is pretty complicated (and then names for the different stages of molting are more confusing than the characters in a Dostoevsky novel). So I will concentrate just on the main flight feathers and tail feathers.
Feathers grow in distinct groups or tracts. The major flight feathers on the wings are the primaries and secondaries. Ospreys have 10 primaries and 10 secondaries on each wing. By convention, they are names Primary 1 (or P1) starting at the wrist, and then working out to Primary 10 (or P 10) at the wing tip. Similarly, the secondaries start at the wrist too (with S1) and then progress to S10 near the body. Between the secondaries and the body is another tract of feathers called the tertiaries.
Ospreys have 12 tail feathers (or rectrices). They are labelled R1 in the middle of the tail, and work out to R6 on both the right and left side of the tail.
The first picture is a great photo of a fishing Osprey taken by John Armitage. I have labelled the major feather tracts on this photo. You can also see the very cool thumb feather - the alula - on the top of the Osprey's wrist. You can't very easily see Iris or Stanley's thumbs when they are perched, since they tend to lie flat on their wings. But now that you know what to look for see if you can spot their thumb feathers.
I have also included photos of Osprey primary, secondary and tail feathers. These are from the excellent "Feather Atlas" from the US Fish and Wildlife Service Forensics Laboratory (
http://www.fws.gov/lab/featheratlas/fea ... mary_adult). Another really interesting thing is how different the primary feathers are in size and shape! These fascinating differences have to do with the aerodynamics of flight.
Study up - this material will be on the final exam! Now that you know some more about Osprey feathers, I will post more on how they replace them in a systematic fashion.
More to follow, Erick Greene (4 foto)