270 BULLETIN" 196, UNITED STATES NATIONAL MUSEUM 



dorsal region decidedly bluish, and ruddy brown of under parts more 

 chestnut." 



Food. — Professor Beal (1915a), in his food studies, treats the western 

 bluebird, the chestnut-backed bluebird, and the San Pedro bluebird 

 all together, as subspecies of the Mexican bluebird. In the 217 

 stomachs examined, the food was found to consist of 81.94 percent 

 animal and 18.06 percent vegetable matter. Among the animal food, 

 grasshoppers formed the largest item, with an annual average of 21.29 

 percent. Caterpillars were a close second, averaging 20.25 percent. 

 Useful beetles, mostly Carabidae with a few ladybirds, amounted to 

 8.56 percent; and other beetles, all more or less harmful, accounted for 

 15.44 percent of the food. Ants constituted 5.38 percent, and other 

 Hymenoptera only 1.26 percent; no honey bees were found. Flies 

 and a few other insects, spiders, myriapods, angleworms, snails, and 

 sowbugs were eaten in very small quantities. 



The vegetable food was made up mainly of fruit, mostly all wild 

 species or waste cultivated fruits picked up late in the season. "Rubus 

 fruits (blackberries or raspberries) were found in 4 stomachs, prunes 

 in 1, cherries in 1, and figs in 3." Elderberries and mistletoe berries 

 proved to be favorite foods ; weed seeds were eaten sparingly, no grain 

 of any kind was found, and a few other items, such as seeds of poison- 

 oak and other Rhus seeds, made up the balance. Of the food of the 

 nestlings, he says: "The real food consists of grasshoppers and crickets, 

 90 per cent, and beetles, 3 per cent, the remainder being made up of 

 bugs, caterpillars, and spiders. * * * The remains of 11 grass- 

 hoppers were found in one stomach and 10 grasshoppers, a cricket, 

 and a beetle in another." 



Theed Pearse tells me that he has seen western bluebirds feeding 

 on the berries of the Virginia-creeper, taking them from the viues; 

 he has also seen them "hawking" insects in the air with a very pretty 

 butterfly flight. They often dart out into the air from some high 

 perch and catch the insects in flight, but more often they watch from 

 some low perch and flutter down to catch their prey on the ground, 

 or hover along over the tops of the herbage to catch the flying insects 

 that they have disturbed. Frank A. Pitelka (1941) saw some of these 

 birds soaring in a strong wind while feeding; he writes: 



The bluebirds would fly to a position in the up-draft some 6 or 8 feet above 

 the ground, there hover for a second or two, and then soar for a few seconds. 

 On a number of occasions, one or two of them remained in a soaring position 

 without movement of wings for 6 to 8 seconds. The birds were foraging for 

 insects, which they caught by dropping quickly from their position in the air. 

 It appeared that the wind was blowing insects upward over the hill slightly 

 above the grass. The bluebirds, hovering or soaring and looking down, watched 

 for them; when prey was sighted, the bird turned about face and flew back to 

 catch up with it. Such a behavior was observed on both the open slopes and 



