Identification of adult male yellow wagtails in winter plumage in western Europe Raül Aymí
A
lthough there are many studies on the plumage of adult males of the different taxa of the yellow wagtail Motacilla complex, most of these refer to the distinctive summer plumage (eg, Milne 1959, van den Berg & Oreel 1985, Shirihai & Gellert 1987). There is, however, little information on their identification in winter plumage; moreover, this information is often insufficient, especially for identifying birds in the hand. The most detailed information on plumages of yellow wagtails can be found in Glutz von Blotzheim & Bauer (1985), Cramp (1988), Keith et al (1992) and Shirihai (1996). This study is an analysis of the specific differences between adult male yellow wagtails in winter plumage. It is based on data collected during ringing campaigns at Ebro delta, Tarragona, northeastern Spain, in the autumns of 1992-95 when more than 11 000 yellow wagtails were trapped. This total included 2186 adult males of which 1669 (c 76%) could be identified and 517 (c 24%) not. The 1669 identified birds belonged to the following taxa (the total number and percentage in parentheses): Yellow M flavissima (237, c 14%), Blue-headed M flava (1143, c 69%), Grey-headed M thunbergi (255, c 14%), Spanish M iberiae (25, c 2%) and Ashy-headed Wagtails M cinereocapilla (9, c 1%) (hereafter flavissima, flava, thunbergi, iberiae and cinereocapilla, respectively) (the taxonomic treatment is in accordance with Sangster et al 1999). For documentation, photographs were taken of which several accompany this article. The study focuses only on adult males since, in most cases, firstwinter birds and adult females are (still) impossible to identify confidently (Cramp 1988, Keith et al 1992, Svensson 1992, Shirihai 1996). It should be stressed that the plumage descriptions are based on an evaluation of plumage characters of birds of unknown geographical origin. General appearance During the (complete) post-breeding moult, from August onwards (Hereward 1979), adult male [Dutch Birding 21: 241-253, 1999]
yellow wagtails acquire the winter plumage which is generally duller than the bright summer plumage. In most winter-plumaged birds, the head is tipped with a mixture of brown or green feathers, masking the ‘summer’ head pattern. The supercilium is less obvious, with creamy or buffish instead of white or yellow colours. In contrast, in dark-headed yellow wagtails, especially thunbergi, some adult males show small faint pale stripes on the head although these are usually absent in summer plumage. When examining the plumage of trapped yellow wagtails, one should be aware that greyish tones to the head may be hidden by differently coloured (greenish or brown) feathers. The upperparts are darker with a browner suffusion, except for the yellowish-green rump. The underparts are duller yellow than in summer plumage. Often, there is a clear demarcation between the yellow belly and undertail-coverts and the more buffy breast and throat which are commonly showing dark markings. Sometimes, these markings form a collar or necklace. In a few birds, the underparts are completely lemon or pale yellow. The pale wing-bars are generally less conspicuous because the coverts usually have a more olive-green tip. The winter plumage is variable in all taxa, ranging from plumages close to the summer plumage to distinctly paler and more greenish plumages which, in some cases, recall the plumage of other taxa. Judging from retraps, the ‘summer-plumaged’ birds may be old males. The bill is blackish, with the base of the lower mandible sepia or bluish although not as bluish as in the breeding season. Main features (cf tables 1-2) Flavissima (plates 255-256, 264) The crown is yellowish-green, often with diffuse bluish shadow spots on the forehead near the bill and above the eye; sometimes the crown is pale buffish-brown. The long and obvious supercilium 241