. [Articles about birds from National geographic magazine]. Birds. The Policemen of the Air 81 the bird. We must learn the nature of its food at all times of year, and then strike a fair bal- ance between its good and its bad deeds; hence the absolute neces- sity for the examination of the contents of birds' stomachs, by which means may be accuratel)' determined not only the kinds of food eaten but their relative quantities. This method is ex- ceedingly slow and laborious, re- quqires a high order of expert ability, and moreover is open to the very serious objection that it necessitates the ta
. [Articles about birds from National geographic magazine]. Birds. The Policemen of the Air 81 the bird. We must learn the nature of its food at all times of year, and then strike a fair bal- ance between its good and its bad deeds; hence the absolute neces- sity for the examination of the contents of birds' stomachs, by which means may be accuratel)' determined not only the kinds of food eaten but their relative quantities. This method is ex- ceedingly slow and laborious, re- quqires a high order of expert ability, and moreover is open to the very serious objection that it necessitates the taking of use- ful lives. So far as possible, the latter objection has been min- imized by utilizing the stomachs of birds killed by naturalists for scientific purposes. This mate- rial, which otherwise would be lost to economic science, renders it unnecessary, except in special cases to destroy birds for the purpose of food examinations. In the above connection it must not be forgotten that when a thorough examination of the food of a given species is once made and the results published, the work is done for all time. The food habits of a species having been once de- termined by this method, no possible exr cuse exists, so far as food investigations go, for further destruction of bird life ; and the more so because the contents of all stomachs examined are preserved as vouchers for further verification, should that be deemed necessary. Passing to a consideration of some of the practical problems presented, it might seem that the relation of birds to agricul- ture were simple, since the question is chiefly one of food. Do birds destroy crops? then of course they are injurious. Do they eat insects? then of a certainty they must be beneficial. But the problems are not to be settled in this off-hand fash- ion. In reality they are extremelv com- plex and are to be understood only after much painstaking study. It has been. From the Diol(^gical Survey SPARROW H.'\WK Which the fa
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