NIGHTHAWK. 471 
to capture flying insects, chiefly of the larger kind, such as 
wasps, beetles, and moths. About the middle of May, or 
later, the female selects some open spot in the woods, the 
comer of a corn-field or dry gravelly knoll, on which to 
deposit her eggs, which are only two, and committed to the 
bare ground, where, however, from the similarity of their tint 
with the soil, they are, in fact, more secure from observation 
than if placed in a nest. Here the male and his mate reside 
during the period of incubation, roosting at a distance from 
each other on the ground or in the neighboring trees; and in 
consequence of the particular formation of their feet, like the 
rest of the genus, they roost or sit lengthwise on the branch. 
During the progress of incubation the female is seen frequently, 
for some hours before nightfall, playing about in the air over 
the favorite spot, mounting in wide circles, occasionally pro- 
pelled by alternate quick and slow vibrations of the wings, 
until at times he nearly ascends beyond the reach of sight, 
and is only known by his sharp and sudden squeak, which 
greatly resembles the flying shriek of the towering Swift. At 
other times he is seen suddenly to precipitate himself down- 
wards for 60 or 80 feet, and wheeling up again as rapidly; at 
which instant a hollow whirr, like the rapid turning of a 
spinning-wheel or a strong blowing into the bung-hole of an 
-empty hogshead, is heard, and supposed to be produced by 
the action of the air on the wings or in the open mouth of the 
bird. He then again mounts as before, playing about in his 
ascent and giving out his harsh squeak till in a few moments 
the hovering is renewed as before; and at this occupation the 
male solely continues till the close of twilight. The Euro- 
pean Goatsucker is heard to utter the hollow whirr when 
perched and while holding it head downwards, so that it does 
not appear to be produced by the rushing of the air. The 
female, if disturbed while sitting on her charge, will suffer the 
spectator to advance within a foot or two of her before she 
leaves the nest; she then tumbles about and flutters with an 
appearance of lameness to draw off the observer, when at 
length she mounts into the air and disappears. On other 
