40 UNIVERSITY OF COLORADO. 



Sylviidse. The willow warbler is an Asiatic bird, reaching America only 

 in Western Alaska. Our other American Sylviidse are the kinglets and gnat- 

 catchers, of each of which there are a number of species. They are very 

 small birds, almost entirely insectivorous, living principally upon small in- 

 sects, including plant lice and scale insects (201). 



Aughey found both kinglets and gnatcatchers feeding on small locusts, 

 one ruby-crowned kinglet containing 29 locusts (202), a surprising number 

 for so small a bird. 



Turdidte. The food of the thrush family as a whole, according to 

 Forbes, averages 61% insects, 1% spiders, 2% inyriapods, 32% small fruits, 

 -'70 grain (203). The young of all members of this family are almost ex- 

 clusively insectivorous. 



Towusend's solitaire, found in our western mountains from Colorado to 

 the Pacific, has been called the fly-iatching thrush, because of its habit of 

 catching insects on the wing, in true flycatcher style. It also feeds largely 

 upon cedar berries and piuyon nuts (204). 



Kobins, where they are abundant and cherries are few, may congregate 

 around the trees and destroy the fruit, but they prefer wild fruit, as do most 

 fruit-eating birds. The planting of wild fruits about the orchards has been 

 strongly recommended, as this keeps the birds away from the cultivated fruits 

 when they wish fruit, yet retains their services in the destruction of the 

 insects which would otherwise render fruit-growing more difficult. The de- 

 struction of olives in California by the robins when their natural food supply 

 failed has already been mentioned. Under ordinary conditions, however, the 

 robins and other thrushes are exceedingly useful. In 330 robin stomachs, 

 animal matter was 42% (chiefly insects), vegetation 58% (wild fruit 

 47%) (205). 



Many robins remain in our Colorado mountains in favorable localities 

 through the winter, and feed chiefly on cedar berries. 



Eastern bluebird, 108 stomachs, representing every month except Janu- 

 ary and November, insects 67 % , spiders 8 % , vegetation 13 % , and 5 stomachs 

 obtained in a canker-infested orchard contained insects 98% (206). In 205 

 other stomachs insects averaged 76% (207). In 187 stomachs of the western 

 bluebird (Sialia m. occidentalis ) insects formed 82% of the contents and 

 vegetation 18% (largely elderberries), while in 14 mountain bluebirds the 

 food was about the same (208). 



(201) Beal, U. S. Biol. Surv., Bull. No. 30, pp. 81-86; Agric. Yearbook for 1904, 

 p. 254. Beal and McAtee, Farmers' Bull. No. 506, pp. 34-35. Judd, U. S. Biol. Surv., 

 Bull. No. 17, p. 108. 



(202) Aughey, First Kept. U. S. Entom. Com., App. II, p. 16. 



(203) Forbes, 111. St. Lab. Nat. Hist., Bull. Vol. I, No. 3, pp. 139-145. 



(204) Coues, Birds of the Northwest, pp. 93-96 ; Birds of the Colorado Valley, pp. 

 44-47. Cockerell, N. Mex. Agric. Exper. Sta., Bull. No. 37, p. 41. 



(205) McAtee, Plants Useful to Attract Birds and Protect Fruit, U. S. Dept. 

 Agric., Yearbook for 1909, pp. 185-196. Beal. How Birds Affect the Orchard, Yearbook 

 for 1900, p. 303 ; The Relation of Birds to Fruit Growing in California, Yearbook for 

 1904, pp. 241-254 ; Birds oi California in Relation to Fruit Growing, U. S. Biol. Surv., 

 Bull. No. 30 and 34. Forbes, 111. St. Lab. Nat. Hist., Bull. Vol. I, No. 3, pp. 88, 96-115 ; 

 No. 6, pp. 5-6, 18-19. Judd, U S. Biol Surv., Bull. 17, pp. 108-109. Palmer, Agric. 

 Yearbook for 1898. p. 261. Beal, Farmers' Bull. No. 54, p. 38. 



(206) Forbes, 111. St. Lab. Nat. Hist, Bull. Vol. I, No. 3, pp. 148-161 ; No. 6, p. 8. 



(207) Beal, Farmers' Bull. No. 54, p. 39. 



(208) Beal, U S. Biol. Surv., Bull. No. 30, pp. 97-100. 



