DIJK J VAN (1975) The Yellow Wagtail as a breeding bird in the Netherlands. LIMOSA 48 (1): 86-99.

Yellow Wagtail Motacilla flavissima = Motacilla flava flavissima In 1972, '73 and '74 the. area between Leyden and Harlem, the so-called Bulbdistrict (see Fig. 1) was investigated for the presence of the Yellow Wagtail Motacilla flava flavissima and the Blue headed Wagtail Motacilla flava flava. In 1972 110 pairs of the Yellow and 174 of the Blue-headed Wagtail were registered. In 1973 these numbers were resp. 100 and 236. In 1974 only a part of the Bulbdistrict was investigated. In view of the intensive working the bulb fields do not look like a proper breeding habitat, however they are among the best yellow wagtail areas of the Netherlands. (15-20 pairs on 100 ha). Most breeding pairs are found in extensive tulip fields in the neighbourhood of pasture, with many ditches, but without barns and hothouses. A survey is given of the distribution of M.f. flavissima. All breeding cases in the Nethel.'lands are mentioned. The Bulbdistrict was not investigated before 1972. Therefore it is not clear whether the occurrence of the Yellow Wagtail is due to a new settlement in this area. Although the occurrence of mixed pairs was carefully investigated during 1972-1974, no mixed pairs were found. Out of 131 well observed females paired with males Blue headed Wagtail, 23 could not be identified as a Blue-headed Wagtail. With the Yellow Wagtail this was the case with 4 of the 45 well observed females. This illustrates the possibility of overlooking mixed pairs. The occurrence of birds showing characteristics of both ?lava mid ?lavissima may be an indication of the existence of mixed pairs. In the Bulbdistrict a yellow wagtail, which may be considered a cross, was seen only twice. These birds were unpail'ed. In the Bulbdistrict the Yellow Wagtails especially occur in the bulb fields just behind the dunes (see Fig. 1). However the ranges of the Yellow Wagtail and the Blue-headed Wagtail are not separated as Mayaud (1952) does state for France. The data of Mayaud concerning Brittany were supplied by Monnat (1973). These data show the importance of the Bulbdistrict. It is the only area of Western Europe, where it is quite normal to find both subspecies on the same square kilometer. A difference in dates of arrival was found (Table 1). The data of Milne (1959) are also mentioned. Small differences were found in the choice of the bulbous plants (Fig. 3). The fact that the second choice of M.f. flava is daffodil and of M.f. flavissima is hyacinth, may be related to the difference in dates of arrival. The annual changes in the number of breeding-pairs of the Yellow Wagtail are not related to those of the Blue-headed Wagtail (Table 2). Finally two opinions concerning the yellow wagtail complex are mentioned. Some authors consider all yellow wagtails belonging to one species, others (f.i. Williamson, Sammalisto) consider the yellow headed forms specifically distinct from the black and grey headed races. According to Voous (personal communication) recognition of a species Motacilla lutea with the subspecies flavissima, lutea and taivana, can hardly be maintained. It is difficult to see how a geographical and genetic contact between the three widely separated subspecies can have existed in the past. The differences between flava and lutea populations may have just as well specific as subspecific value.

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