384 THE NIGHT HA WK. 



called Wilson's Mills, that " in the space of every four or five 

 rods, a female was sitting on her eggs." Indeed, one of the 

 most vivid impressions received in many parts of that north- 

 ern latitude, on a summer's evening, is that of the loud 

 peeping and booming of vast numbers of these birds. This 

 evening flight is really fine. The regular beat of the long 

 pointed wings, now faster, now slower, the bird mounting a 

 little higher, and uttering its characteristic/^ with each 

 accelerated beating of the wings, is somewhat like that of 

 our smaller Hawks, the Sharp-shinned, for instance ; while 

 the graceful tipping of the body from side to side, as it 

 moves in a continued series of curves, affords a still further 

 resemblance. Notwithstanding this analogy to Hawks in 

 flight, however, the Night Hawk in structural affinity is no 

 Hawk at all, but a sort of crepuscular Swift, flying earlier 

 indeed in cloudy weather, and sometimes even in the bright- 

 est sunshine, but generally retiring during all the fore and 

 middle part of sunny days. 



Its flight is generally rapid and high, sometimes seeming 

 to be almost among the clouds, where its frequent motions in 

 the capture of insects show how elevated a part, at least, of 

 the entomological world is. The most characteristic act in 

 the flight of the male is his loud and indescribable boom- 

 ing, as he drops head foremost from his more or less ele- 

 vated position, and, with stiffened wings, the tips pointing 

 downward, cuts a long, abrupt curve. This sound, which 

 Wilson compared to " that produced by blowing strongly 

 into the bunghole of an empty hogshead," he thought was 

 caused " by the sudden expansion of his capacious mouth 

 while passing through the air." Audubon thought it was 

 somehow produced by the wings. The latter would seem 

 to be the more probable conjecture, as one can always see 

 a change in the wings as the noise is going on. The exact 



