386 THE STRUCTURE AND LIFE OF BIRDS CHAP. 



Among its representatives are the Kingfishers and 

 the Nightjars, which thus are near relations of the 

 Swifts. The Humming-birds are often put by them- 

 selves as a separate Passerine sub-order ; but they are 

 still a bone of contention, and it will probably be 

 long before they are allowed to settle in a comfortable 

 corner. 



As affording a typical instance of difficulty, I 

 mention two families, the Piciformes and Coccyges, 

 to many representatives of both of which what is, 

 perhaps, their most striking characteristic is com- 

 mon ; they have zygodactyle or yoketoed feet. 1 How 

 are they to be distinguished ? The Piciformes — i.e. 

 the Woodpeckers and their allies — have a well- 

 marked feather tract on the neck with bare spaces 

 on either side, while in our Cuckoo, who represents 

 the Coccyges in Britain, the neck is all thickly 

 covered with feathers. 



Mr. Mivart's order, the Limicoliformes, illustrates 

 well the difference between the older systems and 

 the new. Most of the birds included were formerly 

 put down as Waders because of their mode of life. 

 These Waders are now grouped with a number of 

 other species which do not wade. Their relationship 

 is shown by the fact that they are born with down on 

 them and arc able almost at once to run ; that they 

 have a divided feather- tract on the forepart of the 

 back ; that they have an oil gland tufted with 

 feathers. These and other characters cause the in- 

 clusion of the Gulls and Terns within the same order 

 as the Waders. 



1 See p. 165. 



