The Rock Wagtails generally appear in Europe about April or May, and almost immediately commence their preparations for breeding. Their nests, usually concealed with great cunning in such holes in the rock or ground as are almost inaccessible, are made of twigs, straw, moss, or grass, heaped roughly together to form the outer wall, the cup-shaped interior being neatly lined with a variety of elastic materials, selected with great care. The delicate blueish green eggs (see Fig. 24, Coloured Plate IV.) are from four to six in number. We have not as yet been able to ascertain whether the male relieves his partner in the work of incubation, or contents himself with amusing her by a kind of dance, performed with ruffled streaming plumage and half-closed eyes, in which he delights to indulge at this season of the year. Both parents, however, assist in tending the young flock, who are reared on the same kinds of insects as form the staple food of the adults; the latter also devour snails and worms, and during the autumn consume large quantities of berries and fruit, including grapes. Their winter migrations take place in September, and often extend over a large portion of Northern Africa; indeed, we have often seen them in the vicinity of the Blue River. In disposition the Rock Wagtail is cautious, sprightly, and restless, passing almost the entire day in active exercise; its flight is extremely light and beautiful, and so rapid as to enable it to seize an insect on the wing; unlike most of the members of its family, it generally flies in a direct line, and, after describing a few circles in the air, hovers awhile before perching. Upon the ground its movements alternate between a tripping step, accompanied by repeated bowings of the head, and the dancing movement alluded to above. Its voice is pleasing, flute-like, and capable of imitating a great variety of notes and sounds; it is for this reason unusually attractive when caged. Count Gourcy tells us that it soon becomes so tame as to greet its master with a song, and testifies its affection by a variety of pretty tricks. We must not omit to mention one strange propensity to which this species is addicted when in captivity, during the season at which its kind usually migrate. At that time of the year it seems seized with attacks of perfect frenzy, rushes round its cage, leaps about, and utterly refuses to take any food that is not forced upon it. This state of excitement only continues for from eight to ten days, and leaves the bird in its ordinary state of health. Throughout the whole course of the attack the little prisoner exhibits a degree of terror which is quite inexplicable, at sights and sounds that at other times would scarcely attract its attention. THE BLUE ROCK WAGTAIL, OR BLUE THRUSH.