Closely resembling the last-named in form and general appearance, the White Wagtail long escaped observation as an annual summer migrant to this country. Its distinctive characters, however, are now almost universally admitted, and ornithologists experience little difficulty in recognizing the two species.
The particular respects in which the White Wagtail differs from its congeners are noticeable chiefly in the summer, or breeding plumage, when the former has a black cap clearly defined against a grey back, while in the latter the black colour of the head merges in the black of the dorsal plumage and no such cap is discernible. In summer both species have the chin black, and in winter the same parts in both are white. In the immature and winter dress it is not so easy to distinguish them, and in form and structure at all ages and seasons no real difference seems to exist. This has naturally raised some doubt in the minds of many as to the validity of the so-called species, a doubt which is strengthened by the circumstance that in regard to haunts and habits the two may be said to be inseparable.
This much, however, seems to be certain, that whereas the Pied Wagtail is generally distributed as a resident species, migrating southward at the approach of winter, the White Wagtail spends only the summer months in this country, and is then very local in its distribution.
Beyond the British Islands the White Wagtail has a much more extensive range than its congeners, being found throughout the whole of Europe, penetrating to the North Cape and even to Iceland, and travelling southward beyond the Mediterranean into Africa, to within a few degrees of the equator.
THE GREY WAGTAIL.
(Motacilla sulphurea.)
Except for the purpose of a momentary comparison, it would be beyond the scope of the present volume to notice the Grey Wagtail here, for this bird does not come under the definition of a Summer Migrant.
It is rather a winter visitant, being most frequently observed in the cold season, although many pairs remain in suitable localities throughout the country to nest and rear their young. Upon this point Professor Newton has remarked that “a line drawn across England from the Start Point, slightly curving round the Derbyshire hills, and ending at the mouth of the Tees, will, it is believed, mark off the habitual breeding-range of this species in the United Kingdom; for southward and eastward of such a line it never, or only occasionally breeds, while to the westward and northward its nest may be looked for in any place suited to its predilections, as above described, whether in this island or in Ireland, where, according to Thompson, it is extensively, though not universally distributed. In Scotland, says Macgillivray, it is rare to the north of Inverness, but it is an occasional summer visitor to Orkney, and in Shetland it occurs towards the end of summer, though it is not known to have been met with in the Outer Hebrides. In the south-west of England its numbers are in summer comparatively small, but it breeds annually in Cornwall and on Dartmoor; and as we pass northward its numbers increase, until in parts of Scotland, perhaps, they attain their maximum. Nests have been reported from Dorset, Wilts, Hampshire, Sussex, and even Kent; but in those counties they are confessedly casual, and only in the case at Chenies, in Buckinghamshire, mentioned by Mr. Gould (‘Contr. Orn.,’ 1849, p. 137), does the species seem to have been more than an accidental settler.”
The Grey Wagtail may be at once distinguished by having the vent and upper tail coverts of a sulphur-yellow, and by its great length of tail. In summer it has a black patch upon the throat, of a triangular shape when viewed in profile, and bordered with white, but in winter this black patch disappears, and the throat is then of a pale yellowish-white.
It has been stated by Temminck and other naturalists who have followed him, that the black throat is the peculiar attribute of the male bird in the summer or breeding plumage; but this is a mistake. Both sexes have a black throat in the breeding season, as I know from having observed them when paired, and from having examined numerous specimens of which the sex had been carefully ascertained by dissection.