Ruggningsstrategier hos sädesärla och gulärla i mellersta Sverige

Abstract

The wing moult of the White Wagtail Motacilla a. alba and the Yellow Wagtail M. f .flava has been recorded since 1973 at Kvismaren, central Sweden. Based on data from 558 White and 78 Yellow Wagtails in active moult the wing moult duration of the former was estimated at 55–65 days and of the latter at 35–40 days. The moult sequence was the same in both species. The only significant difference  was the speed of the moult. The reason for this difference in moult strategy is probably the difference in migration  destination of the two species. The Yellow Wagtail arrives later than the White Wagtail, stays a shorter time in central Sweden and starts the migration towards tropical Africa  just before finishing the moult in the middle of August. Swedish White Wagtails winter in the east Mediterranean, arrive almost a month earlier and leave a month later. It is difficult to compare the present results with data from other parts of Europe as there are plenty of misrepresentations  published some decades ago and quoted in later works. Therefore, methods of moult data evaluation are also briefly discussed.