182 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



been seen, and many times tlie chases seem to be only a form of exercise. 

 Many times when capture appeared certain, the hawk turned away just 

 before reaching the magpie. Once two accipiters flew after the same 

 magpie. Possibly these flights serve to make the magpies less cautious so 

 that capture is easier when the hawk is really hungry. 



One flock, in August, was flushed by a Cooper's hawk that flew into 

 the tree. The hawk pursued the birds as they scattered and then re- 

 formed a group, each one flying erratically and yelling in a sort of "con- 

 fusion chorus." Termination of the chase was not seen, but it was 

 thought that no capture was made. 



Teamwork on the part of two magpies to drive away a sharp-shinned 

 hawk was seen early in November. They took turns maneuvering into 

 position to dive at the hawk as it pursued or fled from the other. The 

 hawk soared upward, which it could do as fast as the magpies could fly. 

 Thus it got above them and out of range of easy flight for them, but 

 it was forced finally to leave the vicinity. 



When a sharp-shinned hawk struck and carried off a Zonotrichia, one 

 magpie fled before it, but four others immediately pursued it to a rose 

 thicket, dived at it three times, and forced it to double back and seek 

 refuge in a more dense thicket. The magpies then stationed themselves 

 around the hawk, one above on a fence post, one in the bushes, and two 

 on the ground, and they remained there watching silently for nearly 

 five minutes. 



In another example magpies in and close to a blue oak were excited 

 over pursuits by a sharp-shinned hawk and a sparrow hawk, both with 

 quarters in the same tree. The former was much more persistent in its 

 drives, pursuing the magpies more swiftly and going closer to them. 

 Each pursuit, however, was abandoned after about 50 feet, and the birds 

 would return to the tree, the hawk in the lead. Behavior when the mag- 

 pies were driven from the ground was much the same. On such occasions 

 a harsh, growling note is uttered by each magpie just before the hawk 

 reaches it, and this may have something to do with the latter's turning 

 aside just before reaching the magpie. No magpie was touched, so far 

 as could be seen. 



Once three magpies, all making the growling note, joined in pursuit 

 of a sharpshin, flying about 10 feet behind the hawk, and following it 

 into a sycamore. Another time this hawk pursued a single magpie, which 

 zigzagged to evade three attempts at capture and growled continuously. 

 The mere presence of the hawk as well as its pursuits seemed to bother 

 the magpies. After these disturbances the magpies moved to denser parts 

 of the foliage of a tree and especially to places where there was a pro- 

 tective barrier of branches close overhead. Flocks pursued by hawks 



