244 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



average 17.7 by 13.4 millimeters ; tlie eggs showing the four extremes 

 measure 19.3 by 13.7, 18.3 by 14.3, 16.2 by 13.5, and 17.3 by 12.4 

 millimeters. 



Young. — Russell and Woodbury (1941) have made a careful study 

 of the nest life of the gray flycatcher at a nest in a juniper in Navajo 

 County, Ariz., where a pair of these birds were raising their second 

 brood for the season in July. According to their obser^^ations, "two 

 broods are raised, leaving the nest in June and early August, respec- 

 tively." They found that incubation lasted 14 days and that the young 

 remained in the nest 16 days. The female alone incubated the eggs, 

 but both parents assisted in feeding the young. During "four hours of 

 observation, the young were fed 30 times, an average of eight minutes 

 between food-bringing visits to the nest and an average of ten feedings 

 per nestling. Tliis means that each young bird was fed on an average 

 once every twenty-four minutes. The periods between feedings were 

 by no means regular. They varied in length from one to twenty-eight 

 minutes and were shorter and much more regular in the early morning 

 than toward noon. * * * So far as we could tell, the food con- 

 sisted entirely of insects. It varied in size from tiny beetles to a 

 butterfly so large that the young could scarcely take it, and included 

 such recognizable forms as grasshopper, yellow wasp, moth, and ant- 

 lion." 



They noted that the parents shaded the young from the hot sun 

 while they were in the nest, and fed them for an estimated period of 

 two weeks after they left the nest. 



Plimiages. — Ridgway (1907) says that the young in juvenal plum- 

 age are similar to spring and summer adults, referred to below, "but 

 wing-bands pale buff instead of gray or grayish white; upper parts 

 brownish gray or gi^ayish brown rather than olive ; gray of chest more 

 brownish, and white of under parts tinged with pale brownish buff." 

 He refers to two types of coloration in adults, one with the lower parts 

 white and one with these parts primrose yellow, but says that "they 

 seem to be mainly seasonal, a large majority of those which are white, 

 or very faintly tinged with yellow beneath, being spring and summer 

 birds while those decidedly yellowish beneath were nearly all obtained 

 in autumn or winter." Also, he says that the upper parts of adults 

 are "more decidedly olive" in autumn and winter specimens than in 

 spring birds. 



We do not seem to know much about the postjuvenal molt of young 

 birds, but adults, apparently, at least begin to molt, if they do not wholly 

 accomplish it, before they go south. Mr. Swarth (1904) says that all 

 the adults he collected in August were "in worn, abraded plumage, 

 many of them in the midst of the autumnal moult with hardly enough 

 feathers to cover them." 



