Allen o)t Insectivorous Birds. 23 



I have compared notes with other bird-lovers who share the same 

 misgiving", based on their own casual study of the subject. But 

 whatever the final outcome of such investigation, sentiment should 

 of course give way to truth. Whether insectivorous birds, con- 

 sidered from the utilitarian side, are beneficial in their relation to 

 agriculture, or positively (at least in many cases) injurious, or 

 merely hold a neutral place, it is far too early yet to decide, for 

 thorough investigation of the subject can be considered as having 

 merely begun. The fact that they destroy large numbers of nox- 

 ious insects is established beyond question; whether they do 

 not at the same time devour so large a proportion of beneficial 

 ones as to fully or more than offset the good they accomplish 

 in the destruction of the former may be considered as an open 

 question, which years of careful observation can alone decide. 

 From investigations now in progress, notably in this country at 

 the hands of Professor S. A. Forbes of Normal. Illinois, it is to be 

 hoped that the data for an intelligent judgment in the matter will 

 be soon reached. To Professor Forbes is due the credit of not 

 only first directing attention to the subject, but of first instituting 

 systematic research respecting the relation of birds to predaceous 

 and parasitic insects. In addition to his own observations he has 

 published a translation * of M. Edouard Perris's memoir on this 

 subject, published in 1S73 in the ••Bulletin mensuel de la Societe 

 d'Acclimatation." t M. Perris, after many years of careful ob- 

 servation, expressed himself as ^convinced that the current ideas 

 respecting the utility of birds are prompted by impulse rather than 

 reflection," and. he adds. " I believe that, if more attention had been 

 paid to the role played by insectivorous birds and to the mode of life 

 of tlie insects which injure us, very different conclusions would 

 have been reached." After reviewing the subject at length, and 

 presenting in detail his long array of tacts, he formulates his de- 

 ductions, calling attention to the fact that birds are scattered here 

 and there in pairs •• while insects invade en masse the trees which 

 they attack, the products of the soil of which they are the ene- 

 mies" : that while birds destroy enormous numbers of insects, 

 these insects are in great part innoxious, while some are eminent- 

 ly useful. " The species really noxious are so few compared 

 with the whole mass, that birds are really of little service. They 



* American Entomologist, new series, Vol. I, 1880, pp. 69-72, 96-100. 



t Republished here from the M6m. de la Soc. roy. des Sciences de Lie^e. 



