THE OOLOGIST. 



187 



Animal matter, 63 per cent. 



Vejjetable matter, 35 per cent. 



Mineral matter, 2 per cent. 



()f the animal food, beetles are by far 

 the most relished, forming nearly one- 

 half of the whole amount. Next are 

 the grasshoppers and crickets (Ortho- 

 ptera), forming about one-tifth of the 

 animal food consumed. Then comes 

 the caterpillars, forming somewhat 

 less than one-fifth, and then the spiders, 

 thousand legs and bugs, forming the re- 

 maining one tenth. 



Only eight per cent, of the beetles 

 consumed are among the beneficial 

 predacious ground varieties, and by 

 the consumption of a great volnme of 

 crickets, caterpillars, weevils, click and 

 leaf beetles, a ratio is established, de- 

 cidedly in favor of the Thrasher. 



Before rendering a complete verdict 

 on the Thrasher, we must follow his 

 food supply through the entire season. 

 In the case of the Wren we 

 found this bird subsisting on an 

 animal diet almost entirely through- 

 out the entire season. With the 

 Thrasher it is different; he changes his 

 diet with the ripening of the fruit, and 

 as he eats more fruit he takes a smaller 

 number of insects, and vice versa. For 

 Instance: Early in April when the 

 Thrasher first arrives from the South, 

 animal food is much more plentiful and 

 the Thrasher consumes at least, three 

 times as much animal food as vegetable, 

 and as the insects are very plentiful 

 even before the vegetable food is ripe, 

 the excess of animal food continues and 

 increases until about the latter part of 

 May it reaches a maximum of 7 to 1. 



When the vegetable element begins 

 to ripen, the proportion of animal food 

 to fruit begins to lessen, and about the 

 middle of August to the first of Septem- 

 ber, the ratio changes gradually until it 

 stands inversely 2 to 1. At no time 

 however does the proportion exceed 

 this two to one ratio, leaving quite a 

 iieavy balance to the end of the season 

 on the side of the animal food. 



Notwithstanding the fact that the 

 maximum of fruit consumed, is reached 

 in July, we find that a large number of 

 beetles and ants are also devoured dur- 

 ing this month. 



After the 20th of June the caterpil- 

 lars which have been very largely con- 

 sumed up to this time, begin to fall off 

 in numbers, and their place to be taken 

 by mulberries, buckthorn, etc., and 

 while a few are found in the stomach 

 constantly, still after the above date 

 they fail to increase to any marked de- 

 gree during the remainder of the sea- 

 son. 



The above looks somewhat dark to 

 the value of the Thrasher economically, 

 but after all, out of the general propor- 

 tions of 25 per cent, of vegetable food, 

 we find that only 11 per cent, of it is 

 cultivated, and of tnis, eight per cent. 

 is fruit and the rest grain. 



Mr. Sylvester D. Judd of the Depart- 

 ment of Agriculture, says of this bird, 

 "The economic relation of the Brown 

 Thrasher to agriculture may be summed 

 up as follows: Two thirds of the birds 

 food is animal, the most of the 

 vegetable food is fruit, but the 

 quantity taken from cultivated crops is 

 offset by three times that quantity of in- 

 secc pests. In destroying insects, the 

 Thrasher is helping to keep in check 

 organisms, the undue increase of which 

 disturbs the balance of nature and 

 threatens our welfare. A good example 

 of the result of such irregular increase 

 is to be had in the fluctuations of the 

 Rocky Mountain locust. 



The Brown Thrasher in its present 

 numbers is a useful bird, and should be 

 strenuously protected from gunners 

 and nest plundering boys." 



The Mocking Bird (Mimus polyglot- 

 tos): — The amount of data regarding 

 the food supply of this bird is small, 

 and although its range is large, and in 

 many localities, especially in Texas, the 

 bird occurs in great numbers, the in- 

 vestigations — what few have been made 



