GoatsuckER. JNSECTIV. CAPRIMULGUS. 1387 
bristles lming the edge of the upper mandible are capable of 
diverging or contracting, by means of muscles attached to 
their roots, they of course greatly assist in the capture and 
detention cf its prey.—The flight of this bird, when thus 
hawking, is rapid, and attended with evolutions similar to 
those of the swallow; at other times, when disturbed, it is 
abrupt and wavering, though still buoyant. It breeds on the 
ground, making no nest, but generally selecting a dry spot, 
where the ferns have prevented the growth of the lower her- Eggs. 
bage.—It lays but two eggs, white, marbled with yellowish- 
brown and grey. During the period of incubation, and after 
it has left its noonday retreat, the male utters a very peculiar 
noise, which has been aptly compared to that of a spinning- 
wheel ; this is produced when the bird is perched, with the 
head lowermost. It also utters a shrill cry during its flight. 
In this species, the membrane that lines the inside of the 
mouth is very thin and transparent, particularly opposite to 
the posterior part of the eye, which organ is pretty clearly 
discernible through the membrane. As the mouth opens to 
such great lateral extent, it has been suggested that the bird 
may possibly be capable of turning the eye in its socket, so 
far as to look through this almost transparent veil in a straight 
forward direction, when the mouth is extended in its noctur- 
nal flights. I have consequently directed my attention to this 
point, but as yet without any satisfactory result. 
I have not been able to discover any peculiar muscles at- 
tached to the eye or its coats, that can enable the bird to 
turn it in the direction suggested ; and I may here observe 
also, that the size and prominence cf this important organ 
gives it, in its fixed position, a sufficient field of vision for all 
the purposes of flight and the capture of its prey. 
The winter retreat of the Goatsucker is presumed to be 
in Africa and Asia, as the specimens from both countries cor- 
respond with ourown. According to TeEmMMINCK, it Is com- 
mon in France and Germany, but rare in Holland. 
