No. 4.] BIRDS USEFUL TO AGRICULTURE. 47 



the United States Department of Agriculture at Washington, 

 D. C, should be in the hands of every farmer. It contains 

 excellent colored plates of the more common species, with 

 much on their habits and food. Having made an exhaustive 

 study of the subject, having corresponded with many field 

 ornitholoo:ists and examined the contents of the stomachs of 

 some two thousand hawks and owls, Dr. Fisher says, "It 

 may be stated with confidence that owls are the most bene- 

 ficial of all birds." This bulletin has long been out of print. 

 This Commonwealth could perform no greater service to the 

 farmers than to publish a reprint and distribute it freely 

 among the agricultural community. " Unless the farmer has 

 some means of identifying these birds, hoW is he to distin- 

 guish the good from the bad?" When once fully identified, 

 they may be distinguished as readily as the dift'erent animals 

 on the farm. They are large birds, and their diflferences are 

 fully as well marked as those of the standard breeds of poul- 

 try. The farmer or poultry-man who will make it a rule to 

 shoot or trap only those of the hawks and owls that actually 

 take poultry, will, by his forbearance, benefit mankind. We 

 might go still farther, and say that some even of those that 

 occasionally steal a chicken should be spared for the good 

 they do in the pasture, orchard, meadow and woodland. 



Cuckoos {Family CucuUdce). 

 The cuckoos are about the only birds that were generally 

 known to feed extensively upon hairy and spiny caterpillars, 

 until an investigation in Massachusetts gave evidence that 

 many other birds were killing these insects. This habit of 

 the cuckoos is so conspicuous that it has been observed by 

 nearly all writers who have studied either cuckoos or cater- 

 pillars. The caterpillar habit of the cuckoos became so well 

 known in the work on the gypsy moth that a gathering of 

 cuckoos anywhere was looked upon as a sign of a caterpillar 

 outbreak. It is a well-known fact that these birds eat so 

 many caterpillars that their stomachs sometimes become 

 lined or felted with the hairs from the bodies of the insects. 

 Some of the most destructive insect pests suffer from the 

 attacks of these birds. The tent caterpillar, forest cater- 

 pillar, gypsy moth, brown-tail moth, black-spined caterpillar, 



