228 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



where. The mantle is more uniform, dull, light brown, without the 

 buffy or white edgings ; the throat is pure white, without the dusky 

 streaks ; the breast band is lighter in color and is sometimes spotted 

 "vvith white ; the lower under parts are whiter with fewer dark mark- 

 ings; in old males the belly, flanks, and tibiae often become nearly 

 pure white, but females always have more dark markings on these 

 parts than males. 



In all these plumages there is a seasonal change due to wear. In 

 fresh fall plumage the feathers of the mantle and breast band and 

 the flight feathers are suffused with a grapelike bloom, giving a 

 bluish, ashy tinge to the plmnage ; as this wears away during winter 

 the plumage appears darker or more brownish, producing a very 

 different effect. 



Extremes of the other two color phases are not common, but inter- 

 mediates between them and the normal, or light, phase are often in 

 evidence, especially in immature birds. In the extreme melanistic 

 phase of the adult, the entire body plumage is "warm sepia", or dark 

 sooty brown, except for some white bars and tips on the upper tail 

 coverts and white, tawny, and dusky barred under tail coverts; the 

 wings and tail are merely somewhat darker than in the normal phase. 

 In adults of the extreme erythristic phase the upper parts, wings, 

 and tail are as in the normal phase; the breast band is similar but 

 mixed with "tawny"; the remaining under parts are deep, rich 

 "tawny" or "hazel", streaked on the belly with dusky or black, and 

 the upper and under tail coverts are as in the dark phase. Immature 

 birds show the phase characters in a variable degree. 



Food. — The food habits of Swainson's hawk are highly beneficial ; 

 it is one of the farmer's best friends, for it feeds almost entirely on 

 injurious rodents and insects, Avith a minimum of birds and poultry. 

 Dr. A. K. Fisher (1893) saj^s that of 18 stomachs examined, 7 con- 

 tained small mammals, rabbits, gophers, spermophiles and mice, 8 

 contained insects, 3 lizards, and 3 frogs. One stomach contained 68 

 locusts and another 50 grasshoppers. None contained traces of birds 

 cr poultry. He quotes Dr. C. Hart Merriam as follows : 



Driving along the crest of the plateau just south of the Umatilla River, at 

 about sundovpn, we were astonished to see a very large number of large hawks 

 hopping about on the ground, catching grasshoppers. We counted about 150 of 

 these hawks, and there must have been at least 200 in the immediate neighbor- 

 hood. At first we took them to be roughlegs, but later ascertained that nearly 

 if not all were Swainson's hawks {Buteo swaiiiso7ii). The period between 

 sundown and dark in that region is so short that the birds were still catching 

 grasshoppers when overtaken by darkness. 



About 6 o'clock the next morning I visited the same place and was gratified 

 to find the hawks engaged in making their breakfast of grasshoppers. They 

 were scattered over a larger area than when we saw them the previous eve- 

 ning. Before 8 o'clock most of them had left the hills and settled down for 



