90 BIRDS IN THEIR RELATIONS TO MAN. 



South during winter. Even during the breeding season the 

 young birds and the old males gather nightly to roost in cer- 

 tain woods. 1 



The nest is so well known that we need here only mention 

 its bulky size and the fact that at least two broods of four or 

 five young each are reared during the season. 



Several studies of the food of the robin are on record. 

 One of the most authoritative of these is that of Professor 

 S. A. Forbes, who made two separate investigations of the 

 food in Illinois : the first included forty-one and the second 

 one hundred and fourteen specimens. We have summarized 

 the results in the latter case as follows : Ninety-nine per 

 cent, of the food of eleven robins shot in February consisted 

 of insects : cutworms and other caterpillars constituted four- 

 teen per cent., and the larvae of the white- winged Bibio 2 a 

 two-winged fly seventy-six per cent. These Bibio larvae 

 have repeatedly been found in several widely separated 

 States to form the principal food of the robin during spring. 

 The larvae live in colonies of a hundred or more individuals, 

 and generally feed upon decaying organic matter, though 

 some naturalists have stated that they are capable of doing 

 serious injury to grass-lands. Professor Forbes took one 

 hundred and seventy-five Bibio larvae from the stomach of a 

 single robin. In addition to these insects a very few beetles, 

 grasshoppers, bugs, spiders, and thousand-legs had been 

 eaten. About five per cent, of the food was estimated to 

 consist of beneficial insects. 



Thirty-seven per cent, of the food of nine March robins 

 consisted of Bibio larvae; cutworms and other caterpillars 

 formed thirty per cent. The remaining food elements were 



1 For an interesting account of these little-known ' ' robin roosts, ' ' see 

 Bradford Torrey's book, "The Footpath Way," and Mr. Brewster's ac- 

 count in The Auk, October, 1890. 



* Bibio albipennis, Say. 



