MOUNTAIN BLUEBIRD 281 



varying somewhat according to the date of hatching; I have seen a 

 young bird that had nearly completed the molt on August 20, but 

 usually the first winter plumage is not complete until some time in 

 September. This molt involves all the contour plumage and the 

 lesser and median wing coverts but not the rest of the wings or the 

 tail. In the first winter plumage young birds are practically indis- 

 tinguishable from adults. 



One-year-old birds and adults have a complete postnuptial molt 

 in summer, beginning sometimes before the middle of July, and in 

 some cases it is not completed until well into September. Ridgway 

 (1907) describes the winter plumage of the adult male as "similar to 

 the summer plumage, but blue of upper parts duller, that of pileum, 

 hindneck, back, and scapulars more or less obscured by pale brownish 

 gray margins or tips, the greater wing-coverts and tertials edged with 

 whitish or pale grayish; blue of under parts washed, more or less 

 strongly, with pale brownish gray or grayish brown, especially on 

 chest and sides of breast." 



Of the adult female in winter, he says: "Similar to the summer 

 plumage but, coloration slightly deeper, especially the buffy grayish 

 of under parts." 



There is apparently no spring molt, the colors becoming brighter by 

 the wearing away of the brownish gray edgings. The whole plumage 

 becomes very much worn before the postnuptial molt. 



Food. — Professor Beal (1915a) examined only 66 stomachs of the 

 mountain bluebird and says: "The contents consisted of 91.62 per- 

 cent animal matter to 8.38 percent vegetable. This is the highest 

 percentage of animal matter of any member of the thrush family 

 herein discussed and is equal to some of the flycatchers." The 

 largest item in the animal food consists of beetles; taken collectively 

 they amount to 30.13 percent, but, of these, 10.05 percent belong to 

 three useful families, predaceous ground beetles, tiger beetles, and 

 ladybirds. Weevils amount to 8.11 percent, "the highest record for 

 any American thrush." Ants were eaten to the extent of 12.51 per- 

 cent, a record "not exceeded by any other bluebirds or robins." 

 Other Hymenoptera, bees and wasps, amount to 3.80 percent; Hemip- 

 tera, bugs, to 3.89 percent, consisting of small cicadas, stink bugs, 

 negro bugs, assassin bugs, and jassids; and flies to only 0.92 percent. 

 Lepidoptera, mostly caterpillars, are a regular article of food, amount- 

 ing to 14.45 percent for the year. Orthoptera (grasshoppers, locusts, 

 and crickets) are the largest item of food, averaging 23 percent for 

 the year. "Very curiously January shows the greatest consumption, 

 70.33 percent; August, the normal grasshopper month, stands next 

 with 53.86 percent.". 



Of the vegetable food, he says: "As with most of the other thrushes, 



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