JUKEMA J & RIJPMA U (1984) On age composition and moult of White Wagtails Motacilla alba. LIMOSA 57 (3): 91-96.

White Wagtail Motacilla alba In June-September of 1980 and 1981, 1683 White Wagtails Motacilla a. alba were trapped in tomato greenhouses in NW. Friesland (fig. 1). In 1980, the portIOn of adult (after 1st calender year) birds was 11%, in 198126% (tab. 1). In adults, primary moult started on average on 15 and 17 July, respectively, and lasted 73-74 days (68 days based on birds trapped more than once) (fig. 2, 3). Secondary moult started at primary score 23 and was finished six days after the primary moult was terminated, lasting c. 40 days (fig. 4). Tail feathers were moulted between primary score 3 and 43, lasting 59 days (fIg. 5). Sequence mostly found: SI-S6-S2-S5S4- S3. Juvenile (1st calender year) birds retained their flight feathers and moulted varying numbers of tail feathers (from late June up to the middle of September), tertIals, and secondary coverts (variation probably related to dates of hatching). Body feather moult w.as complete (first birds starting late June, but many bIrds dId ~ot do so before September). Retraps in spnng of bIrds ringed as juvenile during the summer before suggest that retained feathers are not moulted during the winter, when birds have left the area. During the process of moult, no significant changes in body weight were found (tab. 2). In autumn, the retained juvenile outer secondary coverts CO~stItuted a good ageing characteristic. It appeared dIffIcult to sex birds on wing length.

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