CALIFORNIA SHRIKE 175 



The worrying of prey that is difficult to kill is most persistent. Cap- 

 tive shrikes often spend half an hour at a time in attempting to kill 

 large-sized mice and, failing in their efforts, will worry the mice at 

 intervals during the greater part of a day. 



The initial thrust at prey is with the bill. The effective motion is 

 not a jjounding or driving action with the end of the beak but a rapid 

 biting motion of the tip of the lower mandible against the tomial tooth 

 of the upper mandible. The killing mechanism, then, is a ciuick cut or 

 snip of the bill. 



After the initial successful thrust with the bill, a series of rapid 

 biting motions follows and sometimes also shaking or pounding of the 

 prey against the ground or perch. In the case of large animals a 

 shrike commonly stands motionless for several seconds, and often min- 

 utes, after the animal is dead before further disposing of its catch. 



The impaling habit of shrikes is the result of a lack of sufficiently 

 powerful feet to hold the prey while it is being torn to pieces, thorns 

 or crotches being used in order to hold the food vrhile it is being eaten. 

 Once a shrike has killed or injured its prey to the extent that it is 

 incapable of escape, the food is further disposed of in one of two 

 different ways : it is either impaled or else almost innnediately eaten. 

 If the food is smaller than about a centimeter in its greatest dimen- 

 sions, it is swallowed at once or is taken to an elevated feeding or 

 lookout post and there eaten. 



Occasionally the feet are used to grasp small prey so as to obtain a 

 fresh hold with the bill. The degree to which the foot is used in this 

 way varies with individual shrikes. When food is held in one foot, 

 the bird does not use that foot to support its weight. I have failed to 

 note any instances of shrikes holding their prey against a perch or 

 against the ground by standing on it, as do jays and hawks. To peck 

 at or tear at food in the foot, as occasionally is done, the shrike seems 

 required by its structure to hold the foot forvrard of the position 

 normally taken in perching. 



I have seen caged birds repeatedly attempt to ingest food that they 

 either had failed to break up by impaling or feared would be taken 

 from them, Mith the result that they were forced to disgorge. Several 

 times I have seen the foot used to extract objects which were stuck in 

 the mouth. In these instances the foot was not thrust into the mouth 

 but passed along the side of the head, the claws catching hold of 

 projecting parts of the food at the angle of the mouth. 



As a ride large objects that must be impaled before being eaten are 

 carried during flight, in the bill, but occasionally in the feet. Esterly 

 (1917) reports the actions of a California shrike as follows : 



The shrike flew against a window pane near where I was, and dropped a dead 

 "White-crown." When the sparrow was piclied up again it was seized by the 

 neck, and the shrike flew off with it. But before it had gone more than a yard, 



