The Grey Wagtail is a close inhabitant of rocky streams, and we have to go to the more mountainous parts of our islands to find this species “at home.” Like the Pied Wagtail it is a partial migrant, seeking the warmer portions in the south and west during the winter and moving back to the same rushing streams with the return of spring. The nest is placed in one of the loose stone walls so common near its haunts, or on the ground in some cleft of the rocks. The eggs resemble those of the Yellow Wagtail, but are slightly larger. It is a very handsome bird, the handsomest perhaps of all our Wagtails. The back and upper parts are of a deep bluish grey: wings and tail (except the two outer feathers, which are white, a characteristic of all wagtails), dark brown; under parts clear lemon yellow, paler on the vent. Length 7 in.; wing 3·3 in. Female and young resemble the male, but are paler. In summer the male has a jet black gorget. This species has a much longer tail than our other species, the Yellow Wagtail having the shortest tail. Generally distributed throughout our islands but only found during summer near rushing torrents, wandering at other times throughout the country, but always in the vicinity of running water. The note is very similar to that of the Pied Wagtail. THE BLUE-HEADED WAGTAIL Motacilla flava, Linnæus This species resembles the Yellow Wagtail very closely in all respects, and is the common Continental “Yellow Wagtail,” many different races of which are found. It occurs yearly in the south-east of England on migration and sometimes stays to breed. The adults may be distinguished from our Yellow Wagtail by having the upper part of the head and neck, including the cheeks, bluish grey and the stripe over the eye _white_. Young birds are practically indistinguishable from those of our common species, but the eye stripe is constantly whiter. Length 6·3 in.; wing 3·2 in. A closely allied race is _M. beema_, which breeds in Western Siberia and occurs on migration in India. It is very closely allied to _M. flava_, but is paler on the head and has the _cheeks_ and chin _white_. This form has been taken in England on one occasion, viz. in Sussex, in April 1898. Faded and worn specimens of _M. flava_ appear at first sight to belong to this form, so that excessive caution is necessary before finally identifying British specimens as belonging to this race. The Scandinavian form, known as _M. borealis_, with a dark grey crown and _no_ eye stripe, has been obtained on several occasions, and even remained to breed in Sussex in 1906. [Illustration: BLUE-HEADED WAGTAIL _Motacilla flava_ (left) Young (centre); var. _melanocejala_ (right)]