248 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



eyes and crawl over the ground at a very fair rate of speed." Dr. 

 Gayle Pickwell and Miss Emily Smith (1938), who made extensive 

 studies of several nests of this nighthawk, found that the young 

 could move by crawling haltingly, to the call of the female, as much 

 as 6 or 8 inches when not over 48 hours old ; these young birds were 

 hatched between May 25 and 27; on May 29 they had moved 8 feet 

 more, and on June 2, when about 8 days old, they were found 56 

 yards from the nesting site. 



The same observers learned that the period of incubation was 18 

 days in one case and 19 days in another. Incubation was performed, 

 during the daytime at least, by the female alone, but both sexes did 

 their share in feeding the young. 



All feedings w^re by means of regurgitation, wherein the bill of the parent 

 was thrust into the open mouth of the young, the food brought forth by 

 peristalsis in the regurgitation. Each feeding was terminated by a violent 

 agitation of the heads of both the bird supplying the food and the one being 

 fed. * * * Feedings noted were all creipuscular, at 9 p. m. or earlier, or 

 again at 4 : 30 a. m. or later. * * * 



The protective behavior of the young had the following elements: (1) as 

 long as the young were brooded, concealment by the parent bird sufficed as 

 protection for them : (2) flushing the parent would leave the young in 

 crouch-concealment wherein they supplied their own self-concealment through 

 coloration, which became strikingly protective as their feathers advanced ; 

 (3) almost from the beginning these precocial young were able to run to cover, 

 however haltingly, though this cover consisted of the female bird who caused 

 them to run to her by her calling; (4) not until they were about three weeks 

 old were they able to substitute flying for running; (5) the astonishing method 

 of protective behavior presented by the nighthawks was their intimidation 

 display which was first presented when they were approximately 12 days old. 



Plumages. — Dr. Oberholser (1914) has given us full descriptions 

 of the various plumages of this species ; of the downy young nestling, 

 he says: "Upper surface fawn color, clouded or obscurely mottled 

 with mars brown ; lower parts fawn color, unmarked, but paling on 

 the median portion of breast and abdomen. Very young birds, both 

 male and female, before they are full gi-own, are above very pale 

 buff, finely and sparingly spotted with black, and vermiculated with 

 silvery gray; and below, pale buff, with narrow widely spaced bars 

 of dusky or blackish." 



In the Juvenal plumage, the sexes are unlike; he describes them 

 as follows : 



In this plumage both sexes are decidedly lighter and more closely and evenly 

 mottled than in the adult, particularly above. In the male the upper parts 

 are also more uniform, with more ochraceous or gray and less black ; the tail 

 and wing-quills are broadly tipped with buff; the light bars of the tail are 

 more deeply buff ; the white throat-patch is more buffy ; the lower surface 

 duller, more ochraceous, more uniform, less distinctly and less broadly barred. 

 The subterminal bar on the tail is white, about as in the adult. 



