WHITE-THROATED SWIFT 315 



Plumages. — I have seen no very young white-throated swifts, but 

 birds in the juvenal plumage show the same color pattern as the 

 adults, though the colors are duller and less clearly defined. The 

 long, curved claws are highly developed for climbing. 



Food. — As the food of this swift is obtained wholly on the wing, it 

 probably feeds on whatever small flying insects it can capture. Mrs. 

 Bailey (1928) lists "winged ants and other hymenoptera, bugs, flies, 

 dung beetles, engraver beetles, clover root weevils, leafhoppers, etc," 



Clarence Cottam contributes the following report on the stomach 

 contents of white-throated swifts: "In 21 stomachs of the white- 

 throated swift analyzed in the food-habits laboratory of the Biologi- 

 cal Survey, the dominant food items appear to be flies (Diptera), 

 the root maggots (Anthomyiidae) being the most important, with 

 the long-legged flies (Dolichipodidae), the flesh flies (Sarcopha- 

 gidae), and the March flies (Bibionidae) occurring in lesser numbers. 

 March flies make up 100 percent of the food of a bird from Wyoming 

 but did not occur in any of the remaining 20 stomachs. Flies were 

 present in nearly every stomach and formed from 6 to 100 percent 

 of the total contents. 



"Beetles (Coleoptera) were well represented, especially the dung 

 beetles (Aphodius), and entered into the diet of ten of the birds with 

 amounts varying from 2 to 84 percent, although they averaged about 

 10 percent of the total content. Other Coleoptera identified were 

 weevils (Curculionidae), hister beetles (Histeridae), leaf beetles 

 (Chrysomelidae), rove beetles (Staphylinidae), skin or larder beetles 

 (Dermestidae), bark beetles (Scolytidae), and the antlike flower 

 beetles (Anthicidae), 



"Bees, wasps, and ants (Hymenoptera) entered prominently into 

 the bill of fare of about a fourth of the birds and were present as 

 traces in three-fourths of stomachs examined. Bees were found to 

 represent from 1 percent to as much as 86 percent of the total con- 

 tent, and ants in two cases formed over 90 percent of the food. 



"The true bugs were moderately abundant, the most important 

 being stink bugs (Pentatomidae), treehoppers (Membracidae), leaf- 

 hoppers (Cicadellidae), and squash bugs (Coreidae) ; of the last 

 named family, 50 specimens in one stomach formed 67 percent of the 

 content." 



Behavior. — The one striking characteristic of the white-throated 

 swift is its dashing, exceedingly rapid, and erratic flight. Of the 

 three western swifts, Vaux's may be swift, and the black swift swifter, 

 but the white-throated is certainly the swiftest of the three. S. F. 

 Rathbun writes to me : "If there is a faster-flying bird than the white- 

 throated swift, I would like to see it. Always it appears to fly at top 

 speed. At times the velocity of its flight seems beyond belief. The 



