FOOD OF EOBIjSTS AND BLUEBIEDS. 29 



cent, the remainder being made up of bugs, caterpillars, and spiders. 

 In another brood of four, grasshoppers and crickets constituted 97.5 

 per cent of the food, and one stomach contained nothing else. The 

 remains of 11 grasshoppers were found in one stomach and 10 grass- 

 hoppers, a cricket, and a beetle in another. The only vegetable 

 matter in the four stomachs was a single seed of Polygonum. 



Summary. — That the western bluebird is an eminently useful 

 species is so patent that it hardly needs to be pointed out. What- 

 ever harm fruit growers have suffered from birds, none can be laid 

 at the door of the western bluebird. 



MOUNTAIN BLUEBIRD. 



(Sialia currucoides.) 



The mountain bluebird occupies in general the United States from 

 the Rocky Mountains westward. A bird of the higher altitudes, it 

 comes to the low valleys only in winter or during the prevalence of 

 severe snowstorms in the mountains. As settlements encroach upon 

 its range it adopts the habits of the eastern species and utilizes 

 unoccupied crannies for nesting sites. In this the bird is said to 

 be modifying its distribution, for it frequently finds such favorable 

 localities for its nest that it remains and breeds in the lower alti- 

 tudes instead of retiring to the mountains as formerly. 



Food. — Only 66 stomachs of this species were available for inves- 

 tigation and these were not very regularly distributed, none being 

 collected in May and November and only one each in February and 

 October. The contents consisted of 91.62 per cent animal matter to 

 8.38 per cent 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. It consists almost entirely of in- 

 sects and a few spiders. The vegetable food is made up of fruit. 



Animal food. — Beetles collectively amount to 30.13 per cent of the 

 food and make the largest item. Of these 10.05 per cent belong to the 

 three useful families — predaceous ground beetles (Carabidae), tiger 

 beetles (Cicindelidse), and ladybirds (Coccinellidse). In these items 

 the food of the mountain bluebird exceeds that of any other species 

 of thrush previously discussed. "Weevils or snout-beetles (Ehyncho- 

 phora) were eaten to the extent of 8.11 per cent, the highest record 

 for any American thrush. As these are all injurious insects and 

 some of them the worst pests in the insect world, this record for 

 weevil destruction in some measure offsets the eating of useful 

 beetles. The remainder of the beetle food was of more or less 

 harmful families. 



Ants were eaten by the mountain bluebird to the extent of 12.51 

 per cent. This record is not exceeded by any other bluebirds or 

 robins. They were taken rather irregularly and in July amount to 



