This section is from the book "The Balance Of Nature And Modern Conditions Of Cultivation", by George Abbey. Also available from Amazon: The Balance Of Nature And Modern Conditions Of Cultivation.
The Grey Wagtail (Motacilla melanope) is not such an abundant species as the Pied Wagtail, and is found chiefly in the hilly and mountainous districts of England and Scotland, and is fairly common in Ireland. It frequents streams and other places where there is water, and is of relatively solitary habits. It is not quite so large as the Pied Wagtail. It is slate-grey above, the wing coverts, quill feathers and six central feathers of the tail being black, the throat is black, and the under-surface bright yellow. The nest is built early in spring in a bank, much like that of the Pied Wagtail, and usually contains five eggs, or sometimes seven may be found, of a creamy-white colour, speckled with light brown blotches. Frequenting brooks and other watercourses, also ponds and marshes it destroys numbers of fresh-water molluscs, such as Limnaea trun-catula and L. pereger, well-known hosts of the liver-fluke (Distoma hepatica), subsisting entirely upon insects. The grey wagtails migrate southward in the autumn, and though some may remain in Devon and other southern counties of England, they generally leave the British shores in the autumn.
The Yellow Wagtail (Motacilla Rayi) arrives in England in March or April and is generally distributed over England and southern districts of Scotland, but in the northern parts of that country and in Ireland the Yellow Wagtail is rarely seen. It is mainly of a yellow colour; upper parts olive or greenish-yellow, and lower parts of a canary or light yellow. The female is not so bright in colour as the male. The bill and feet are black. It is about 6½ in. in length. On arrival in this country the Yellow Wagtails frequent marshes and grass-land, but soon pair and go to cultivated land, hunting for insects, even following the plough, and devouring millipedes, wireworms, and other insects as they are disturbed or turned up. Breeding begins early. The nest, usually made on the ground in grass or tufts or on a bank, is composed of dried bents and roots, with dried grass and wool or hair, or even fine roots, for a lining. Four to six eggs are laid, varying in colour from pinkish-brown to a darker brown. Two broods are sometimes produced in a season. After young are hatched, the birds move off to meadows, pastures and marshes, where they follow cattle and sheep for the insects around them.
Found near watercourses, ponds, and marshy places they devour fresh-water molluscs, amongst them snail-hosts of the liver-fluke. The Yellow Wagtails leave Britain in September and October.
The White Wagtail (Motacilla alba), regarded as a mere variety of the Pied Wagtail, is only an occasional visitant to this country. The Blue-headed Wagtail (Motacilla flava) is even more rare in Great Britain.