208 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



There have been March arrivals reported, but these are exceptional. 

 Large flocks, some of them numbering thousands of individuals, 

 have been seen during May. Many of these southern records may 

 be representatives of the southern form, Chordeiles minor chapmani. 



It is not necessary to search the isolated retreats away from the 

 habitations of man for the first nighthawk arrivals. In fact, they 

 are more likely to appear in the midst of our populous cities and 

 towns, where they may be seen flying high above the graveled roofs 

 that later are to be the scene of their nesting activities. 



Courtship. — The courtship of the nighthawk is an ardent and 

 amorous performance on the part of the male. He may be seen at 

 twilight or early dawn uttering his sharp peent calls as he flies in 

 wide circles sometimes hovering or soaring in the air high above the 

 proposed nesting site. At more or less regular intervals he swoops 

 down often within a few yards of his mate. Just as he seems about 

 to dash into the ground he makes an abrupt upward turn, the 

 vibrating primaries producing the well-known boom. After these 

 preliminary aerial perfonnances the male alights on the ground or 

 graveled roof near the resting passive female. He now stands on 

 his feet instead of resting his body on the ground. His tail is widely 

 spread like a fan and wagged from side to side while the body is 

 given a peculiar rocking motion. The throat is frequently puffed 

 out, displaying a large white patch, which is ordinarily concealed 

 when he is at rest. Synchronized with the throat distension is the 

 uttering of guttural croaking notes. In producing these notes the 

 bird holds the beak tightly closed, so that the throat membrane is 

 distended by the pressure of the air emitted from the lungs. Under 

 these conditions the sound waves originating at the syrinx beat 

 against the tense membrane, producing notes of a striking and 

 peculiar resonant quality. These notes are not uttered under ordi- 

 nary conditions and constitute a very important part of the courtship. 



The female, as far as outward manifestations are concerned, does 

 not seem to be at all impressed by these extraordinary antics. The 

 male at times in seeming desperation flies directly over the female 

 uttering a sharp peent. He may then circle the female several 

 times but even to this she seems unmoved. At times, when he 

 approaches too near, the female will take a short flight, alighting 

 a few yards away. The male follows and the performance described 

 above is repeated. Eventually the courtship terminates in copulation. 



The aerial evolutions of the male, including the downward plunges 

 and "booming," are continued throughout the nesting period, but 

 after the young are hatched his effervescent energies are directed 

 in part to securing food for his offspring. With regard to the court- 

 ship of the nighthawk, Charles W. Townsend (1920b), who gave 



