Retrapped Nuthatch recovers from missed moult (12 September 2003)
I previously posted photos of an adult female Nuthatch Sitta europaea, caught in my garden on 24 February 2003, that had missed most of the moult in autumn 2002. I am delighted to say that today (12 September 2003) I caught her again and this year she has undergone a completely normal full moult.
When caught on 24 February, all of her primaries, secondaries and the left half of her tail were pale, bleached and abraded feathers grown in 2001. She looked obviously pale and with clear contrast between her (moulted, bluish-grey) mantle, inner medians, head and uppertail coverts (and with a few outer greater coverts as well), and the rest of her feathers that were at least 18 months old. More detail of the wing showed that last year she moulted the small and middle feathers of the tertials but none of the secondaries or primaries: these were symmetrical. Note the abrasion, which is not as bad as might have been thought for such old feathers, but the bleaching is very striking, especially at the tips of the longest primary feathers. Finally, she had moulted all of the right half but none of the left half of her tail.
I don't know the cause of such abnormality but expect that it might be disease or some sort of hormonal upset during the moulting season. I would guess that most birds to which this happens will fare badly and would be unlikely to survive. It is interesting to have this proof, firstly that she survived a year without growing new feathers, and secondly that the problem, whatever it was, has gone away.
There was, incidentally, no other indication that she was 'out of condition' and her weights (21.4g in February, 21.1g in September) were within the normal range for Nuthatches.