I think the folded wings show what to me is the key. This bird has a retained
S3 in the right wing, much browner than the rest of the flight feathers,
clearly a different generation feather from the rest of the wing. The primary
coverts also appear brown and worn. On the left wing it has retained S3 and S4.
So the question becomes: is it more likely for an adult to fail to completely
replace flight feathers, leaving S3 and S4 as retained older feathers (this is
what Pyle says we should “look for” and he also mentions the possibility of an
adult retaining old primary coverts).
OR is this a young (SY) bird that, in addiation to the usual tertials and
secondary coverts, has replaced all its primaries and all but one or two of its
secondaries, but retained a juvenal secondary and juvenal primary coverts?
Chris
