312 NATURE SKETCHES IN TEMPERATE AMERICA 



the year, two in October and the remainder during the spring 

 migration. All but five of these birds were shot in extreme 

 northern Illinois, at Waukegan, Evanston, and Blue Island. 

 Eighty-four per cent of the food consisted of insects, four 

 per cent of spiders, and twelve per cent of thousand-legs; 

 ants amounted to fifteen per cent, butterflies and moths 

 nineteen per cent, and Diptera only to three. Beetles make 

 thirty per cent of the food, four per cent are water beetles, 

 five per cent scavenger beetles, two per cent weevils, and two 

 per cent plant beetles. Leaf chafers and spring beetles amount 

 to one per cent each — the latter chiefly of the genus Melanotus. 

 Eight per cent of the food was bugs, nearly all of which were 

 predaceous. Grasshoppers (Tettix and Tettigidea) make seven 

 per cent of the food." 



" Respecting the number of beetles eaten by this bird, we have 

 to remember that it passes us at the time of that great out- 

 pouring of insect life connected with the pairing of the spring 

 beetles which we have already seen to have a very significant 

 relation to the food of i)irds. It rides northwards, in fact, 

 on the crest of this beetle wave, and we find the same excess 

 of predaceous beetles in its food which occurs in the food of 

 the other thrushes at the same season. Concerning the two 

 October specimens taken in northern Illinois, I need only say 

 that they had eaten ants, caterpillars, ground beetles, weevils, 

 burrowing bugs, and grasshoppers, spiders, lulidjv, and larvae 

 of March flies. The hai)its of this bird suggest that the principal 

 drain on the number of predaceous beetles may be due to the 

 depredations of the migrants at the sea.son of the greatest 

 exposure to these insects; and that the complete destruction 

 of resident birds would affect the number of these carnivorous 

 insects much less than would at first seem likely." 



After reviewing this array of in.sect food consumed by one 

 species of bird, it is readily conceived what a pronounced effect 

 the combined action of many species would have in controlling 

 the number of insects. Especially is this factor of insect 

 control an important one in the spring, when it is remembered 

 that many of these hibernating insects are the sole survivors 

 of many that have i)erished through the cold winter. 



Other birds have been studied in relation to their food supply 



