122 Summer Studies of Birds and Books CHAP. 



himself, and uttering cries that make the meaning of 

 the motion unmistakable. 



The tail- motion of the Wagtails, if I am not mis- 

 taken, is no great mystery; it is no more than a 

 nervous trick, which in their case, as in that of so 

 many others, expresses happiness and satisfaction. 

 The Pied Wagtail which I watched on the lawn half 

 an hour ago showed me this as plainly as possible. 

 When he first alighted on the lawn he " wagged " his 

 tail, and every time he caught an insect he did so. 

 The Gray Wagtail, a quieter bird, as we have seen, 

 has developed a habit of constant motion which is, 

 indeed, second nature with him, and as plainly 

 speaks his content with his surroundings as does 

 the flicker of the Eedstart in the orchard. 



But we are not yet quite at the end of the matter. 

 Every one who has noticed these tail-motions at all 

 must have been struck by their constant correlation 

 with those white feathers which are so conspicuous 

 in the Wagtails. And the Wagtails are by no means 

 alone in this peculiarity ; for it is astonishing how 

 many European birds show white either in their tails 

 or tail-coverts, and how large a number of these have 

 some nervous trick which makes this white conspicu- 

 ous. 1 The Moorhen is a good example. I have seen 



1 When the tails are not made conspicuous by white (or in a few 

 cases red) feathers, there is as a rule no special tail - motion. 

 Skulking birds, like many of the Warblers, have neither motion nor 



