Correspondence 161 



be taken into account, except as "unknown" or as "miscellaneous." 

 If the tables or diagrams do not show this must we not conclude that 

 the writer has discarded the unidentified material? Wilcox,^ v,ho ex- 

 amined over 200 stomachs of the robin in one year, says: "The 

 determination of insect remains in the stomachs of birds is a very 

 difficult and i^erplexing task, and one which is not all pleasant, since 

 nearly all the material is in the very worst condition imaginable, and 

 mutilated and jiartly digested fragments of several species of insects 

 being mixed up in utter confusion. The elytra, mouth parts and tarsi 

 are, of course, usually left to tell their tales, as are also the harder parts 

 of all other insects, snails, myriapods and the seeds of the various fruits; 

 but the soft bodied larvae and earthworms are too often macerat>id almost 

 beyond recognition." (p. 118.) 



Too often the adherent of stomach examination publishes only his 

 percentage results, without the detailed data upon which his percentages 

 are based, which are necessary in a strictly scientific piece of work. 



Most ornithologists. will concede that field observations on the food of 

 birds possess certain advantages; those who have had much practice 

 in this method will understand that it yields results with far greater 

 accuracy than its critics are ready to admit. 



No field worker, I presume, would claim that field observations alone 

 would give us a full knowledge of the economic status of a species. It 

 will be claimed, however, that such observations contribute to such knowl- 

 edge very largely, if not with parity, in comparison with other methods. 

 Furthermore, this method is not destructive of life, which would become 

 a fact of importance in the study of any rare species. It is not par- 

 ticularly reassuring to read the boast of having killed so many thousands 

 of nestling birds in order to determine what their food had been for 

 the last two or three hours. The writer recognizes that under certain 

 circumstances it may be justifiable, but nevertheless, in the judgment of 

 many this criticism will apply to the stomach method. 



It would seem, when a careful review is made, that the hypercritical 

 apostle of stomach examination ought to be more cautious whither he 

 slings. To paraphrase the revie^^er's closing remark, what is needed 

 above all on the part of iconoclastic reviewers is more certainty and less 

 quibbling, and more hard work in the field and laboratory that there 

 may be developed an appreciation of the difficulties to be encountered 

 in productive efl^^ort. 



Sioux City, Iowa. 



* Wilcox, E. V. Bull. 43, Ohio Agric. Exp. Sta., 1892, pp. ll.j-1.31. 



