YELLOW-BILLED MAGPIE 173 



and the bird carries an extra one. Limbs of blue oak, black locust, and 

 valley oak are used as an anvil for pounding the acorn, but the valley 

 oak seems to be the favorite. Apparently the rougher bark and larger 

 branches make this tree more satisfactory. 



In hammering an acorn the bird does not strike with vertical blows; 

 instead the bill comes down toward the feet at an angle of 80° from the 

 horizontal. The Bill is not lifted immediately on striking the acorn but 

 is pushed into it. Sometimes hundreds of blows, in series of about 20, 

 are required to open the shell. A magpie exhibits jealousy over an 

 acorn in its possession and normally takes it to some secluded spot 

 away from the other birds. Also it appears reluctant to leave one when 

 disturbed by a person. Effort is likely to be made to retrieve an acorn that 

 is dropped by accident. However, on their own accord, they commonly 

 discard any acorn that proves difficult to open, and many partly eaten 

 ones are left for another occasion or where some other bird can get 

 them. These traits are exhibited with respect to other kinds of food, but 

 they are more easily watched when large objects like acorns are con- 

 cerned. 



Additional mannerisms are shown by the following account of an 

 incident watched on the Hastings Reservation. Four foraging magpies, 

 on November 18, assembled under a live oak and looked up at the 

 periphery of the tree where another one was clinging to an acorn-laden 

 limb, which bent to a 60° slope under the weight of the bird. An acorn 

 was wrenched free and carried to the ground. Another bird flew up and, 

 after searching in three places, found a suitable acorn. This was seized 

 at its base, transverse to the axis of the bird's bill, and wrenched free. 

 The acorn fell to the ground, and the bird followed it swiftly, but too 

 late, for one of two magpies on the ground had reached it and then the 

 retriever refused to give it up. The dispossessed bird returned to the 

 tree and obtained another acorn, which also fell. But this one it followed 

 so swiftly that the other two birds could not reach it, and it retrieved 

 and carried away the acorn with a squawk. The bird that had stolen the 

 first acorn deserted it to try for the next one to fall and then returned 

 to the first acorn and began to hammer it. As many as eight magpies 

 were seen carrying acorns under this tree. Nearly all the acorns were 

 obtained by loosening them and following them to the ground. If no 

 other magpie was close, the bird got its acorn ; otherwise a bird already 

 on the ground got it. Each acorn finally retrieved was carried away, 

 placed underfoot, and hammered open. 



Other kinds of food obtained regularly from plants in this vicinity 

 were figs and fruits of poisonoak, coflFeeberry, and grapes. The fruits of 

 coffeeberry ordinarily are carried to some perch where the pnlp is ex- 



