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 (Spizella 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 lowa 
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 
