16 CUCKOOS AND SHRIKES IN RELATION TO AGRICULTURE. 



The habit of killiog small animals and hanging up their bodies has 

 given the shrike the appropriate generic name Lanius, which means 

 'butcher.' The name 'Butcherbird' is more properly apjjlied to the 

 larger northern bird, while to the smaller and more southerly species 

 the title ' Loggerhead ' shrike is given. 



Difterent diets affect in time the structure of an animal. Special 

 parts are developed for procuring and digesting food. But the role 

 that food habits play in the production of such variations has not yet 

 been fully worked out. All structures are necessarily developed and 

 maintained in direct relation to function. Shrikes have special struc- 

 tures suited to their peculiar feeding habits. So long as the northern 

 shrike or butcherbird is ^-estricted to an animal diet, because of the 

 relative scarcity of insects at the North during most of the year, it 

 must be more of a meat eater than its southern cousin, the loggerhead. 

 The struggle for existence in the North is so keen that the butcher- 

 bird, during cold weather, must hold itself in readiness to fly at the 

 first bird or mouse that is sighted. 



The food habits of the shrikes, so far as determined from the exami- 

 nation of 155 stomachs, collected during every month of the year, from 

 Saskatchewan to Florida and from the Atlantic to the Pacific, are very 

 similar to those of the sparrow hawk; that is to say, the food con- 

 sists of mice, small birds, and insects, the latter mainly grasshoppers. 

 Both birds are much less insectivorous in cold than in warm weather — 

 the oncoming of winter and consequent increasing scarcity of insects 

 necessitating a change in food. 



In discussing the insectivorous habits of the shrike, it is hardly nec- 

 essary to state that the destruction of grasshoppers is a great service 

 to the farmer. The shrike also devours a large number of beetles, and 

 often eats caterpillars, wasps, and spiders. Since it takes practically 

 no vegetable food, it can not injure crops, unless indirectly, by killing 

 birds and insects that prey upon insect pests. The birds selected, 

 however, are for the most part seed eaters and consequently less valu- 

 able than the insectivorous kinds; and if it be granted that the harm 

 done by the destruction of one of these birds is counterbalanced by 

 the killing of one mouse, tlien it follows that the harm done by the 

 shrike in killing birds is completely offset. Furthermore, the attacks 

 of the shrike are often directed against the English sparrow, now so 

 obnoxious in many i)urts of the United States. Concerning the insect 

 food, it may be safely stated that the percentage of noxious grass- 

 hoppers is four times as great as that of the useful ground beetles. 



In considering the relation of the shrikes to agriculture, it must be 

 remembered that one inhabits a fertile country wliere cultivation yields 

 heavy crops, while the other lives in a northern region where agricul- 

 ture amounts to very little. Therefore, the good or harm done by the 

 northern butcherbird nuist be mainly accomplished when it migrates 

 south into the United States. From the present limited investigation, it 



