1897] NOTES AND COMMENTS 147 



habitually passes by one kind of insect to look for another which is 

 more appetizing, and there seems little evidence in support of 

 the theory that the selection of food is restricted to any particular 

 species of insect, for it is evident that a bird eats those which by 

 its own method of seeking are most easily obtained. Thus, a ground- 

 feeding bird eats those it finds among the dead leaves and grass ; 

 a flycatcher, watching for its prey from some vantage point, captures 

 entirely different kinds ; and the woodpecker and warbler, in the 

 tree tops, select still others. It is thus apparent that a bird's diet 

 is likely to be quite varied, and to differ at different seasons of the 

 year. 



" In investigating the food habits of birds, field observation can 

 be relied on only to a limited extent, for it is not always easy 

 to determine what a bird really eats by watching it. In order to be 

 positive on this point, it is necessary to examine the stomach 

 contents. When birds are suspected of doing injury to field crops 

 or fruit trees, a few individuals should be shot and their stomachs 

 examined. This will show unmistakably whether or not the birds 

 are guilty." 



In his notes on the tree-sparrow (Spizdla monticola) Mr Beal 

 shows that the stomachs of these birds in winter are crammed with 

 the seeds of weeds, and he estimates that in the State of Iowa 

 alone, if there are only ten birds to a square mile, no less than 875 

 tons of weed seed are consumed by this single species' in a single 

 season, basing his calculations on the modest estimate that each bird 

 eats one fourth of an ounce a day for a winter season of 200 days. 

 This may be used as an argument by the ignorant to show how 

 much they eat of grain in the summer, but examination of stomachs 

 of the same birds in summer shows conclusively that one third 

 of the bulk is made up of insects (not available for consumption in 

 the winter), grass and weed seed, and a little oats. The young 

 birds also are largely fed on insects. 



We cannot spare space to quote the statistics of other birds, but 

 the story is much the same in each case. It is for the farmer 

 to decide whether he cares to spare a little grain in the summer in 

 order that his fields may be kept comparatively free of weeds 

 from year to year, or whether he prefers to kill the birds and have 

 his pockets emptied by paying for weeding, and the destruction of 

 hosts of insects which are kept at bay solely by the birds he so 

 religiously endeavours to destroy. 



We have already one work on the economic ornithology of Great 

 Britain on the. lines of this bulletin (" Ornithology in relation to 

 Agriculture and Horticulture," by various writers, edited by John 

 Watson, 1893); but a real benefit would accrue to the farmers in 

 enabling them to know accurately their friends and their enemies 



