Tuesday, June 06, 2006

Losing feathers - a question for Blakeman

Lola missing feathers -- 6/4/06 from Http://www.palemale.com
Photo by Lincoln Karim

Referring to the photo above, Karen Ann Kolling of Rhode Island writes:
Noting Lola's feather situation on Lincoln's web site and having seen PM with a similar thing going on, it might be interesting to post about how and how often feathers are replaced, for those of us ignorami out in the boonies...

I sent her note to John Blakeman and he responded obligingly:

Red-tails (and most other raptors) have standard molting patterns, dropping feathers in distinct sequences.
The molt usually begins with the dropping of the inner-most pair of primaries. As new feathers come down, adjacent feathers are dropped, with primaries dropping in an outward direction, secondaries in an inward one.
Nearly at the same time of the dropping of the first primaries (within a week or two), the dropping of a tail feather begins, starting with one of the two center feathers. A second central tail feather is often quickly lost, leaving a hole of the two missing central tail feathers.
Tail feathers are dropped in pairs from the center outward.
Growth of the missing long flight feathers can take 10 to 14 days or so. When the new feathers attain full length, adjacent flight feathers will be dropped.
When new feathers reach full length, they are still "in the blood," soft, with interior blood flow. The feather is not fully functional and strong until the interior blood vessels dry up, which can be a few days after the feather are fully extended. Feathers still in the blood can be easily bent or injured and such damage is permanent. But red-tails are particularly attentive in not engaging in combative killing events that could permanently damage new, still-soft feathers.
That's a major reason the molt occurs in the summer, when there is plenty of easy-to-catch food. In winter, when prey can be hard to find, the hawk's feathers are usually able to withstand a good deal of bending. One seldom sees a wild red-tail with damaged feathers. During the molt, they are very attentive to feather care.
Injured raptor feathers should never be plucked. Falconers "imp" the permanently bend feathers, inserting and gluing in slivers of bamboo or plastic in the straightened, hollow feather shaft. We usually snip off the damaged outer length and imp on a new feather length from a formerly molted feather held for this purpose. Federal falconry regulations allow falconers to keep their molted feathers for just this (and no other) purpose. We aren't allowed to stick a fine red tail feather in our hat.
And for the public's information, no one is permitted to pick up a molted hawk feather (of any size or condition) and take it home. All migratory bird feathers are prohibited from possession for any reason not specifically included in Migratory Bird Treaty Regulations.
If anyone sees a red-tail feather on the ground, leave it lie. It is illegal to pick one up and walk away with it. If, however, one might see a feather being plucked and dropped by a known Central Park red-tail, it would be acceptable to pick it up and store it in a plastic bag for DNA analysis. If we had a fresh feather from every CP red-tail, DNA analysis could create the missing genealogy.
Species in other hawk genera, such as falcons and accipiters, have different molting patterns.
Occasionally, a wild red-tail will "over molt," dropping a new feather in September or October that was newly grown at the beginning of the season. We falconers see this sometimes with our captive birds, and there is every indication that this occurs because the bird has an abundance of food.
Large raptors such as eagles often fail to molt out all of their feathers in single season. Red-tails and smaller raptors usually have a complete molt each year.
The start of the molt can vary markedly. I've had my birds drop long flight feathers as early as April, while the same birds began the molt in other years in late May or even early June. I've never been able to determine what starts the molt. I think it's just a bit random.
One of the pictures of Lola by Lincoln Karim shows the recent loss of the first primary on each wing. I'd say that she dropped the feathers about a week before the photo. She will drop one of the two center tail feather soon.
None of this describes the molting of the smaller body ("covert") feathers, or the interior down feathers, another detailed topic.
--John Blakeman