v A Chapter on Wagtails 121 



spinal cord and the brain, and may become an index 

 or reflector of what is going on within that brain. 

 Tails may of course be used in different ways ; the 

 cat waves its tail when it is angry, the dog when it 

 is pleased. That is merely matter of habit ; but in 

 each case the motion is the result of some affection 

 of the nervous system. Now the nervous system of 

 birds is very sensitive, if we may judge by their 

 restlessness, and by the extreme vigilance and 

 rapidity of their sight and all their motions. And 

 this in many birds, and especially in small ones, is 

 apt to show itself in the tail, which is flickered 

 horizontally, as in the Eedstart, or jerked upwards, 

 as in the Wren and Moorhen, or twitched several 

 times in a minute, as in the Yellowhammer and 

 Eeed Bunting, the Wheatear and Whinchat, and 

 others. 1 The motion may mean either simple satis- 

 faction, or sometimes distress and alarm. With 

 most of the birds I have mentioned the former is 

 the cause, though not, I think, invariably; but 

 watch a Ked-backed Shrike as you approach his 

 nest or young, and you will see a good example of 

 the effect of anger on a tail. He sits on the top of 

 the hedge, swinging his tail from side to side, as well 

 as up and down, with a motion quite peculiar to 



1 A motion of the wings often accompanies that of the tail ; 

 and in some birds, as the Chats and most Buntings, a note of 

 some kind is uttered at the same time. 



