134 BIRD BEHAVIOUR 



young of one family differ in type from those of 

 another nearly allied to it ; this being that of the 

 young of the Sand- Grouse (Pterodidce) which are 

 active runners, though with a very different type 

 of down from that of young game-birds proper, it 

 being more like true feathers. Yet the Sand-Grouse 

 are supposed to be allied to the Pigeons, in which 

 the young present the consummation of the help- 

 less type, blind and pap-fed, with the down nearly 

 always scanty, and sometimes even wanting, as in 

 the bare black young of the Nicobar Pigeon (Calcenas 

 nicobarica), which reminds one of a new-hatched 

 Cormorant, Cormorants and Gannets being bare 

 at first and downy later on. 



But the Plovers are also a related group, and 

 these the Sand-Grouse approach in their aborted 

 hind toes, in their flight and notes, and in laying 

 spotted eggs on the bare ground, as much as 

 they do the Pigeons in their short legs and vege- 

 tarian habits. Those Pigeons also which have 

 adopted a ground life and assumed a coloration 

 strikingly like that of Sand- Grouse, nevertheless do 

 not resemble them more than other Pigeons other- 

 wise, so that possibly the Sand-Grouse are not so 

 near Pigeons as some anatomists have made out. 



There is only one family of birds in which the 

 young are not definitely known, and that is the 

 extraordinary little group of Finfoots (Heliorni- 

 thidce), of which only three species are known, all 

 from warm climates, one African, one East Indian, 

 and one South American. In appearance and 



