38 B.(/. ExTO^roi-oracAL SocrETY. 



ture, horticulture, trade, and sport ; it treats of species importaut to tlie farm#r, •tlie 

 fruit-grower, tlie game-dealor, tlie milliner, and the sportsman ; iu short, it is the 

 practical application of the knowledge of birds to the affairs of every-day life. The 

 study of the relations of birds to agriculture is as intricate and difficult as it is 

 broad aud comprehensive. Its successful ijrosecution presupposes not only an 

 accurate knowledge of classification, distribution, migration, and habits, but also 

 an acquaintance with the measures which have been adopted for the preservation of 

 useful or the destruction of noxious species. Theoretically, it should be one of the 

 first branches of oi-nithology to receive attention; in reality, it has been one of the 

 last." 



It is as regards the value or otherwise of birds to the farmer that I wish to 

 direct your attention. I do not claim to be an entomologist, and I do not intend to 

 analyse the food of insectivorous birds to try and prove that this species feeds on 

 harmful insects, and that one on useful ones. Such information is readily obtainable 

 from the numerous valuable bulletins on the food of birds published by the Biological 

 Survey of the U.S.A. Government and other publications. I am anxious rather to 

 plead for a more general treatment of the subject; that is, from the standpoint of 

 the balance of nature, to show how Importaut it is to consider the matter from this 

 point of view and how easily one can be led astray by ignoring it. 



To first of all take the case of seed-eating birds, there is no doubt that almost 

 any one can be shown to be a destroyer of millions of weed-seeds during the course 

 of a year. Many people naturally think that it would only require a suflicient 

 number of certain birds to entirely rid them of certain weeds. Nature, however, has 

 made other arrangements by which the weeds shall remain iu spite of even plagues 

 of birds. A certain number of seeds are permitted to pass through the birds' alimen- 

 tary sj'stem unharmed. Professor Collinge has recently shown this in the Journal 

 of the Board of Agriculture, where he gives the result of experiments in the 

 germination of seeds from bird-excrement as follows : 133 weeds of 7 species were 

 grown from 3S droppings of the house-sparrow, 52 of 7 species from 3S droppings of 

 the g'reenflnch, and 96 plants of 9 species from 50 droppings of the bullfinch ; proving 

 that seed-eating birds are greater distributers of weed-seeds than is generally sup- 

 posed. He finally says : " We cannot rely on weeds being kept down by birds, and 

 the exjjense of cultivation to eliminate weeds is, I believe, not reduced in the slightest 

 by the_ action of birds." In conclusion, he states that he cannot regard seed-eating 

 birds as beneficial. 



Now, to take the case of insect-eating birds, I cannot d,o better than quote from 

 a review of recent literature on the subject of economic ornithology in the Auk for 

 January, 1913, where the writer compares the value of controlling insect pests by 

 natural and artificial means. He says : " There is a deep-seated and persistent 

 (because founded on love of ease) idea that if natural enemies are only sufficiently 

 encouraged and protected, crop-production free from the annoyance of insect pests 

 will be assured. That this is a dream impossible of fulfilment is evident from the 

 fundamental interrelations of living things. Natural enemies have developed because 

 there was an excess of individuals of certain species that could be destroyed without 

 any permanent decrease in the numbers of the species as a whole. In creatures with 

 annual or shorter generations, as is the ease with most insects, all but an exceedingly 

 small proportion of the offspring must die without participating in reproduction ; the 

 way of their taking-off is unimportant. They may as well be eaten as to starve, dry 

 up, or freeze. Whatever happens to the supei'numeraries, a small but fecund mino- 

 rity remains. The average number of the species is about the same from year to 

 year. If there is an excess of individuals, under natural conditions, that satisfies 

 the demands of enemies, without endangering the existence of the species. What an 

 overwhelming excess of a species there must be where we give over acres or hundreds 

 of acres to pure cultures of its favourite food-plant. No wonder there are constantly 

 recurring outbreaks with which natural enemies are unable to deal." He further 

 states : " AVheu we consider the degree of insect-control necessary to the commercial 



