Page:The Zoologist, 4th series, vol 6 (1902).djvu/50

24 Differences between immature Blue-headed and ordinary Yellow Wagtails.—Can any reader give some definite characteristics to distinguish immature birds of the Blue-headed Wagtail (Motacilla flava) from those of the ordinary Yellow Wagtail (M. campestris)? Mr. Howard Saunders, in his 'Manual,' apparently regards the white eyestripe as the distinguishing feature of M. flava. Dr. Bowdler Sharpe describes this eye-stripe as "tawny buff," and winds up with the statement that "young birds of M. flava are scarcely distinguishable from those of M. campestris." During the last three autumnal migrations I have paid considerable attention to the point, and it would be interesting to see if the experience of others in any way coincides with my own. In September, 1899, I was looking out for M. flava amongst some flocks of M. campestris on the Norfolk coast. I scrutinized these flocks daily through strong glasses, and at last encountered a bird which struck me at once as being different to the ordinary run. Seen at a distance, it appeared darker above, especially about the head. I shot it and set it up, and may mention that a good judge, who saw it, momentarily took it for a Grey Wagtail. I showed it afterwards to Mr. J.H. Gurney and Mr. Southwell at Norwich, both of whom agreed that it was a specimen of M. flava. The eye-stripe was light tawny buff, and the throat white; the upper parts of the head and back dark greenish grey, not brownish. Against this darker ground the light margins of the wing-coverts and tertiaries showed up more than in M. campestris. In September, 1900, I was at Aldeburgh, and Yellow Wagtails were abundant on Thorpe Mere. I shot one or two to compare with my Norfolk bird, but once only saw anything to remind me of it; and this bird I failed to secure. Last year I was again in Norfolk, and came across a Wagtail which, as it ran, reminded me of the 1899 bird. I shot it, and have since compared the two. The later one agrees exactly in the hue of its upper parts and dark head; the eye-stripe is ill-defined but light, while the throat, though light, is certainly not so white as in the former bird, but has a yellowish tinge, especially at the sides. Still, comparing them with my Yellow Wagtail, I believe that they are both specimens of M. flava, and would suggest that the real difference between the two species at this age lies in the different hue of the upper parts, especially the head. The natural fading of a stuffed bird will doubtless soon reduce both eyestripe and throat to white, and I cannot help thinking that these distinctive marks have in consequence been overrated, and that M. flava is a commoner bird in autumn than has been supposed; but that, as in the case of the Marsh-Warbler, an eye to variation in the shade of colour is the main requisite for its detection. In the Pied Wagtail