174 THE BIRDS OF SHERWOOD FOREST. 
of the American species, and the whole of the Australian 
genus Hwrostopodus, have the rictus without bristles, 
and yet have the claw strongly pectinated. 
All these theories are plausible, and I believe all may 
be occasionally exemplified. The feathers of the head 
may be infested with vermin, and the bird then natu- 
rally uses its foot as the only instrument whereby it can 
free itself from its tormentors, and so brings its toothed 
claw into use. Again, chafers and other large insects 
may be at times caught with the foot, in the manner of 
the kestrel ; the long bristles of the rictus may become 
clogged or displaced in use ; the foot again is the only 
means at the bird’s disposal for straightening them, and 
in this the toothed claw may assist. I cannot think, 
however, that any of these uses is the one for which 
most of the species of this family are furnished by their 
Creator’s wisdom with an instrument so peculiar. ; 
My own observations have long led me to suspect 
another use. JI am not sure whether the same idea has 
not been mentioned by some naturalist, though I know 
not by whom; but, apart from this, I am more and 
more convinced of its probability, and it has been still 
further confirmed by a minute examination of the foot 
of our European species, as well as some exotic ones. 
The larger number of species composing the family 
of the Caprimulgidz do not perch across a bough, as 
all other perching birds do, but lengthwise; and it is 
for this peculiar use that I believe the foot to be spe- 
cially formed. 
In the ordinary position of perching birds, the twig 
or bough is grasped by the foot, and thus a firm hold 
is obtained, the weight of the body, by tightening the 
tendons, increasing the stability ; but it is evident the 
