THE UT OF A BIRD’S FROCK. a3 
of feet so largely prevail, the bare tract on the back 
is placed variously. A glance at a nestling swift or 
woodpecker, in comparison with a nestling sparrow 
or robin, will show a striking difference in the ar- 
rangement of the plumage. 
There stands directly between the ostrich forms 
and the fowl forms a singular group known as Tina-. 
mous, which have so many characteristics of each that 

Switts. 
systematists have wrangled much over its position. 
It is resting now, perhaps rather securely, in the fowl 
group, partly because its plumage shows bare tracts, 
as no ostrich form does. 
The origin and purpose of the various tracts is yet 
rather obscure, and will doubtless remain so. Only 
the ostrich forms, the penguins, the screamers (and 
