116 



SUBKIXGDOM VERTEBRATA. 



the former replaced by the brown-olive of the latter, the two 



"birds could hardly be 

 distinguished.* 



Motacillidae. The 

 Wa g tail incessantly 

 flirts its tail up and 

 down, accompanying 

 each elevation with a 

 jerking spread. This is 

 due to the length of the 

 tarsi (Fig. 184), which, 



Mafia sialis, Blue-bird. J. on the l ower i ng O f t he 



bill, throws the centre of gravity in front of the feet and 

 gives the body a constant tendency to tumble forward. The 

 quickly-expanding tail striking against the air, raises the 

 head a^ain with little effort. 



Fig, ISO. 



190. 



Philomela luscima, Nightingale. 



Motacitta alba, White Wagtail. 



Sylvicolid.36 (wood- warblers). The Nightingale oi* 

 Europe has been famed from time immemorial for the sweet- 

 ness of its voice. It is a shy bird, but its song is occasion- 

 ally heard during the day, though it is most pleasing in the 



* Their social nature corresponds as fully as their physical, and the hlue-bird 

 would fljrure as appropriately in the beautiful legend of " The Babes in the Wood "as 

 the traditional robin -redbreast. 



