64 U.S. NATIONAL MUSEUM BULLETIN 237 pabt i 



elderberry (Sambucus) , which constitutes the bulk of this item, and was found 

 in 26 stomachs. 



Seeds of various weeds and some grain constitute 14.7 percent of the food. 

 Oats were found in 9 stomachs and wheat in 7, but the amount was insignificant. 

 The rest of the vegetable food consists of the seeds of more or less troublesome 

 weeds, of which the grosbeak eats a very considerable quantity. 



The stomachs of 17 nestlings were mcluded in the study. The 

 youngest birds had been fed ahnost entirely on insects, averaging 

 more than 90 percent, mainly caterpillars and pupae. The older 

 birds had been given a larger percentage of beetles and other insects. 



Weston (1947) states that, in Strawberry Canyon, a "high per- 

 centage" of the food of this grosbeak consisted of the California oak 

 moth, which defoliates the live oaks. He saw them eating the worm- 

 like larvae, and found pupa cases broken open. ''Innumerable 

 winged adults were also captured and eaten, although the wings 

 were dropped before the bodies were eaten." He also lists 18 species 

 of plants, parts of which were eaten. 



In the Yosemite region, Grinnell and Storer (1924) noted black- 

 headed grosbeaks "feasting on the wild blackberries which were then 

 ripening in abundance." And "two males were seen feeding upon 

 the hearts of cherry blossoms. These birds were working rather 

 rapidly and a blossom would drop every fifteen of twenty seconds." 

 And, in western Nevada, it was observed by Robert Ridgway (1877) 

 "to feed, in May, upon the buds of the grease-wood {Obione conjerti- 

 folia)." 



Joe T. Marshall, Jr. (1957), discussing the species without racial 

 identification, states that it eats numerous pine seeds evidently 

 taken from open cones. He says, further, "A pair fed on the green 

 seeds of a prostrate milkweed. Another grosbeak ate mistletoe in a 

 ponderosa pine. * * * In a flowering Arizona oak, one * * * fre- 

 quently reached toward the catkins with its biU. This fem.ale was not 

 at first recognized as a bird, for it resembled instead a chipmunk or 

 small squirrel by constantly keeping its head down and body hori- 

 zontal; it actually crawled along the horizontal twigs." He also 

 describes two migrant adult males which fed in Prunus virens, remain- 

 ing within a few yards of each other for 45 minutes. The birds were 

 searching for certain leaves rolled up half their length, each enclosing 

 a large green caterpillar. "Each bird would fly to a slender twig, 

 bending it so as to cling head-down : as it rocked up and down it would 

 deftly pluck the leaf and then fly a few inches to normal posture on a 

 steady twig. With a few quick movements of the bill the grosbeak 

 would tear open the rolled up leaf, discard it with a shake of the head, 

 and wind up with the caterpillar in its mouth. It subdued each 

 caterpillar by biting along its length, then swallowed it whole. These 

 dexterous operations were achieved entu-ely by the biU with no help 



