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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Pattern, extent, and time aspects of the postjuvenile moult in stonechats (Saxicola torquata)
Auteurs :	Heiner Flinks, Auteur
Type de document :	Article
Dans :	Vogelwarte (40(1-2) Oct., 1999)
Article en page(s) :	11-27
Langues:	Allemand
Résumé :	Pattern, extent and duration of moult as well as the influence of the hatching date in first-year birds was studied in 320 stonechats from 1991 to 1996 in Northrhine-Westfalia, Germany. The age of 60 birds could be determined exactly. 9 birds were caught twice during moult. The moult of the body feathers is most significant for the postjuvenile moult. Earliest start of moult was at July 2 (+- 8 days), latest finishing at October 31 (+- 12 days). Stonechats of the first brood (born between the beginning of April and mid-May) start their postjuvenile moult at an age of 68 +- 11 days, those of the second brood (born between mid-May and end of June) at an age of 46 +- 10 days, and those of the third brood (born between the beginning of July and August) at an age of 34 +- 6 days. Average duration of moult is 71.1 days in birds of first broods, 68.2 days in birds of second broods, and 57.5 days in birds of third broods. Some birds of third broods start migration to their wintering grounds with active moult. The duration of moult in retrapped birds varied between 45.5 and 79.2 days with an average of 60.1 days; this represents a progress of 1.58 moult-score points per day in body-feathers (of a total of 95 score points spread over 19 feather areas with score from 0-5 each). Moult starts first at the breast, flanks and the middle back. It progresses more or less symmetrically on both sides towards the chin, fore back, upper and undertail coverts. With short delay moult starts at the crown and continues towards forehead and the nape. The feathers around the ear and some feathers of flanks are the last areas where moult occurs. The growth of the second set starts shortly before or simultaneously with the moult of the body feathers and finishes when the body feathers are replaced 65%. Moult of wing-feathers starts on the upper side with lesser coverts, to progress with the median coverts. A short time after the lesser coverts, the greater coverts start moulting. Simultaneously tertiaries, carpal covert, and the first and possibly the second alula can be replaced. The extent to which these feathers are changed depends on the age of the bird. The earlier stonechats are born in the year the more extensive are the part of new feathers of these areas. None or all of these feathers may be replaced. Stonechats born late during the year replace at least the greater coverts 7 to 10. The primary coverts and the primaries are moulted only exceptionally (three birds). Only 17.5% of the birds of the first broods renew tail-feathers during the postjuvenile moult. Partial moult of the wing feathers, tail-feathers, alula, and carpal covert was not different in males (x = 5.6; s = +- 3.7 growing feathers) and females (x = 6.3; s = +- 3.8 growing feathers). The calendar effect in the duration (for each day that hatching is later as compared to the average, the termination of moult is advanced for 0.6 days) and the pattern of moult in stonechats is compared with other species. The significance of the moult of the four innermost greater coverts (white speculum) is explained by their function as sexual and intraspecific signal. Criterions for age determination in the second year before postnuptial moult are given, based on the varying extent of the partial moult of the greater coverts, carpal covert, alula and tertials.

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