Slaapplaatstrouw bij in warenhuizen overnachtende Witte Kwikstaarten Motacilla alba

In the years 1978-1984 nearly 6000 White Wagtails, roosting in greenhouses, were ringed in two Dutch provinces: Friesland in the north, and Noord-Brabant in the south. Young birds were less frequently retrapped in later years than adults. This difference was statistic significant in Friesland, so in Friesland adults show more site fidelity than young birds. Much more adult males than adult females were trapped. Probably females stay longer roosting on or near the nest. As a consequence, of the birds ringed in their first calendar year, also more males than females were retrapped in later years. However there is no difference in site fidelity between the sexes: the proportion of earlier ringed birds in second calendar year birds is the same in males and females. Adults did not show a difference in site fidelity between the sexes either. Young birds from early broods show more sitefidelity than later ringed birds. This may indicate a difference in winter survival between early and late born young wagtails. The higher site fidelity of adults in Friesland compared to Noord-Brabant is not only caused by a bigger catching effort, but is probably also mirroring a higher mortality in Noord-Brabant.