More odd moults (18 December 2003)

Within a few minutes of each other on 18 December 2003 I mist-netted in my garden two non-passerine birds that showed odd moult patterns.

The first was a Sparrowhawk Accipiter nisus, a second-year bird (Euring age 5), hatched in 2002. Keen readers will remember that I showed photos of another female Sparrowhawk of similar age caught on 23 January 2003, but - unlike the January bird - I did not have to look hard to find retained juvenile feathers on today's bird, as she had undergone a particularly un-extensive moult in the summer. She had retained five of the twelve tail feathers, the outermost two (t5 and t6) on both sides, and t2 on the left side only. The retained (juvenile) rectrices can readily be seen to be browner, and more faded and abraded, than the grey feathers grown in her first full moult in summer 2003.

She had also retained, symmetrically on both wings, four juvenile secondary feathers (s4 and ss7, 8, 9, counting ascendantly, from the centre of the wing towards the body). Sparrowhawks have 14 secondaries. All raptors moult the secondaries from two or three centres, thus having only small gaps where the feathers are missing and enabling them to keep a high level of flight ability during their lengthy moult. It is perhaps, therefore, not surprising that the unmoulted feathers are not all adjacent. According to Professor Ian Newton FRS, who has probably handled more Sparrowhawks than almost any other British ringer, 'most Sparrowhawks replaced all of their flight and tail feathers at each moult, but occasional individuals examined in winter had kept one or two worn secondary or (less often) tail feathers from the previous year' (The Sparrowhawk, T & A D Poyser, 1986). The book does not give figures, but Ian Newton always chooses his words carefully and the implication of the phrase 'occasional individuals' is that it is not common; and there is no indication of any bird having retained so many juvenile secondary or tail feathers.

As you can see, this bird was quite a handful and difficult to photograph on my own! Like the female caught on 23 January 2003, this bird appeared greyish-blue on the upperparts. There is a view amongst some birdwatchers, and some authors, that female Sparrowhawks are brown.

The head shows the characteristic 'female look', with a white line over the eye, and the iris is becoming deep yellow, with orange flecking around its edge. This colour will intensify as the bird gets older. The last photograph, below, shows a comparison with a first-year female Sparrowhawk ringed by Dave Riley at Woolston in September. The contrast in colours (plumage, eye and bill) is striking:

As I released the Sparrowhawk, it flew off and flushed a male Great Spotted Woodpecker Dendrocopos major into the mist-net. It was immediately obvious that the woodpecker looked odd, with many feathers being faded and brown rather than the expected glossy black:

Clearly this is an 'adult' bird - hatched in 2002 or earlier - that had missed part of its full moult, normally carried out in June-August. In this, it resembles the Nuthatch Sitta europaea caught earlier this year, and whose photos featured twice, first when caught in February and then when retrapped in September, when she had returned to normal after a complete moult. It seemed that none of the woodpecker's tail had been moulted this year, making the rectrices about 17 months old. They were in poor shape, especially the central four, which woodpeckers use to brace themselves against tree-trunks. The photo below shows a comparison of a normal Great Spotted Woodpecker's tail (left) and the rectrices of this bird:

Its wing moult was not symmetrical. On its right wing it had moulted all of the lesser, median and greater coverts as well as the carpal covert and all of the alula; whilst on its left wing it had moulted most of the lesser coverts, and all but the largest feather of the alula, but its median and greater coverts had not been moulted this year. The photo below shows its left wing, in which it had moulted a block of four innermost primary feathers, along with the associated primary coverts (and we can't take that for granted in any woodpecker! - first-year birds always, and adults often, moult the primaries without moulting the primary coverts).

The final photo shows a comparison of the upper part of this bird's left wing with the right wing of a normal adult Great Spotted Woodpecker at this time of year, this one being a bird that had some unmoulted feathers in its median coverts and alula. The unmoulted feathers on today's bird are obviously much more bleached and abraded.

Has something odd happened this year to cause these funny moult patterns?


David Norman.


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