Ardea
Official journal of the Netherlands Ornithologists' Union

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Newton I. & Marquiss M. (1982) Moult in the Sparrowhawk. ARDEA 70 (2): 163-172
1. Sparrowhawks resident in south Scotland moulted once each year, mainly in the period May (females) or June (males) to September/October. For most of this period, the birds were also breeding. Moult took about 100-120 days in the average male, and about 110-130 days in the average female, with wide variation between individuals. In some birds of both sexes, moult was arrested for a period during the time the young were being fed. Birds in arrested moult were found between late June and mid-August, and some individuals that were re-trapped were in the same state for periods up to 37 days. 2. Among females, the onset of moult was strongly correlated with the onset of egg laying, and birds which began laying late also began moulting late. For anyone laying date, however, the start of moult varied somewhat, with most birds beginning in the period between 5 days before the first egg to 10 days after. At least up to age 3 years, moult began progressively later with respect to laying date. Individuals which in this respect were early for their age in one year tended to be early for their age in other years, and vice versa. 3. Males began on average about 26 days later than females, and (on a small sample) the start in particular individuals showed no obvious correlation with laying date (of mate), nor with age. The later start in males meant that they retained full wing efficiency while they were hunting to provision their incubating mates. 4. On average, birds of both sexes started moulting earlier in lowland, where laying was earlier, than in upland. 5. In the primary feathers of the wing, replacement progressed from the innermost outwards. In the secondaries, moult tended to start within a short time at 3 different foci, around secondaries, 5, 10 and 1. From 5 and 1 moult spread inwards towards the body, and from 10 it spread both inwards and outwards, with much variation between individuals. In the tail, the most frequent sequence of replacement in each half was 1, 6, 3, 4, 5 and 2, but again the sequence varied widely between individuals. Particular birds showed no great consistency in the sequence with which they replaced their secondary or tail feathers from year to year.


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