286 ANIMAL LIFE IN THE YOSEMITE 



of indigestible material regurgitated by the hawks, was preserved for 

 subsequent detailed examination (fig. 38). The pellets we find to consist 

 of feathers of birds, and skin and hair of mammals, all of which had been 

 eaten along with the flesh of the victims. Later, when the processes of 

 digestion had removed the meat, the residue had formed into dense pellets 

 and had been disgorged. A great deal of this mass of material, of course, 

 was in a condition to defy recognition; but the following species were 

 identified, in each case to the extent indicated. Chipmunk: Much hair and 

 some skin. Red-shafted Flicker: Single feather from breast. Sierra 

 Grouse : A single, characteristically marked feather from a young bird ; 

 a Canadian Zone species, like the Allen Chipmunk mentioned above. 

 Blue-fronted Jay: Bones of one wing with two typical feathers attached; 

 also scattered feathers. Sacramento Spurred Towhee: One covert from 

 the right wing of a juvenile bird. Western Tanager: Several feathers. 

 California Yellow Warbler: Several feathers. Audiibon Warhler: Several 

 feathers from adult birds. Western Robin: One claw and part of a toe, the 

 latter with a dark horny sheath indicative of an adult bird; also feathers 

 from juvenile bird. There were also remains of June beetle, ladybird 

 beetle, and of other insects, which may have been taken only incidentally 

 because of their presence in the gullets or stomachs of the avian victims. 

 These hawks are not known to hunt for insects. 



Like other hawks the Cooper Hawk is often subjected to attack from 

 kingbirds. At Pleasant Valley we saw one mobbed in flight by Western 

 Kingbirds and Brewer Blackbirds until it took off in rapid retreat, and 

 near Coulterville one seen flying across a canon was harried by kingbirds 

 until it was driven down close to the brush and there lost to sight. 



Western Goshaw^k. Astur atricapillus striatulus Ridgway 



Field characters. — Size of Eed-tailed Hawk, but of more slender build, with shorter, 

 more rounded wings, and longer, more slender tail (pi. 44b) ; patch at either side of 

 rump, as seen in flight, white. Upper surface uniform dark slate gray in adults, dark 

 brown in immature birds; under surface white, finely barred wdth black in adults, and 

 broadly streaked with dark brown in immatures. Voice: A series of loud, insistent, 

 staccato cries, MJc, MJc, Tcdh, with a ringing quality, sometimes varied to Tcee-dr. 



Occurrence. — Kesident in small numbers in Canadian Zone on west slope of Sierra 

 Nevada. Visits Yosemite Valley in winter. Lives in or about thick forests. 



The Western Goshawk is the largest of the three bullet hawks, which 

 make birds their principal victims. Its large size enables it to prey upon 

 all manner of game; hence, even though present in but small numbers, it 

 must play an important part in limiting the population of quail, grouse, 

 and pigeons in the higher mountainous districts. It is known to visit 

 mountain ranches in fall and winter and to capture domestic chickens. 

 Quite likely at times rabbits and the larger squirrels also fall victims to it. 



