214 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



whereas the female took charge of the nest at night in the case of a 

 pair of birds lie observed at Exeter, N. H. Dr. A. A. Allen (1933) 

 states that the male takes his place on the eggs in the evening while 

 the female is away feeding. Forbush (1927) states that both male 

 and female share in incubation. On the other hand, J. H. Bowles 

 (1921), who made an intensive study of the nighthawk, records only 

 the female incubating the eggs. T. G. Gentry (1887) states that incu- 

 bation "is the exclusive labor of the female" but that the young are 

 cared for by both parents. It is evident, if the above statements are 

 all true observations, that there is considerable individual variation in 

 the behavior of the male in regard to incubation. In my own in- 

 tensive studies of several pairs of nighthawks that nested on graveled 

 roofs at Brunswick, Maine, I have never seen the male incubating 

 the eggs. In the case of one nest under daily observation the birds 

 were subject to study day and night by a relay of observers for a 

 considerable part of the incubation period. The same held true for 

 a pair of nighthawks studied in northern Michigan. Furthermore, 

 visits made to numerous nests revealed in those cases that only the 

 female was incubating the eggs, although the male was often very 

 near to the female or to the eggs. My observations agree with the 

 statement of Gentry that the female does all the incubating, but tlu^ 

 male in most instances assists in caring for the young. 



The behavior of the birds in relation to the nest and eggs and 

 correlated with the time of day, the weather, environmental condi- 

 tions, and the activities of other birds can be illustrated by field 

 notes taken on June 20, 1921. These notes are representative of ob- 

 servations taken throughout the nesting season. The nest under 

 consideration was located on the graveled roof of a two-story high- 

 school building at Brunswick, Maine, a village of about 7,000 inhab- 

 itants located on the Androscoggin River. There are numerous giant 

 elms and other shade trees along its streets, and the spacious j^ards 

 and gardens present an environment attractive to a large number of 

 birds. The times given throughout the following notes are eastern 

 daylight saving: 



June 20, 1921. 2 : 50 a. m. Cloudy, moon hidden by clouds, clear 

 near the eastern horizon where the stars shine brightly. Entered the 

 blind on the roof at 3 a. m. Female incubating the eggs. Her eyes 

 were wide open when viewed with the flash light. 



3 : 20 a. m. The female has been quiet during the past 20 minutes 

 but has now shifted her position and is facing northeastward directly 

 toward the first faint light of dawn. (Daily observations revealed 

 that the nesting bird usually faced the sunrise in the morning and 

 the sunset in the evening. In other words, she oriented herself to- 

 ward the source of light preceding the times she anticipated leaving 



