392 University of California Publications in Zoology [Vol. 11 



bird changes its food according to the age and season of the 

 year." Also that "the moment when certain insects inundate 

 a country with individuals without number, . . . coetaneously, 

 this very abundance seems to invite a crowd of different species 

 of animals to feed upon them." It was not till 1882-1885, nearly 

 twenty-five years later, that Forbes clearly pointed out these 

 interrelations between birds and insects. 



Prevost concludes: "I am in the course of proving that 

 birds are in general much more useful than injurious to our 

 crops, and that even in respect to the greatest part of the graniv- 

 orous species the evil which is done to us at certain times is 

 largely compensated by the destruction of insects which they 

 accomplish at other times. It is important, then, that we do 

 not destroy these species, but only divert them from the crops 

 when they injure them. Their destruction would permit, with- 

 out counterbalance, the development of many species of insects 

 more fatal still to agriculture. The study of the alimentary 

 regimen has furnished me also some information which I believe 

 useful in comprehending the reunions, the separations, and peri- 

 odical emigrations which are observed so commonly among birds. " 

 (See Prevost, 1858, translation by J. W. P. Jenks.) 



Since the work of Prevost, economic ornithology has grown 

 rapidly. Germany has probably been most active in the work. 

 Hawks and owls have received the most attention throughout 

 Europe, probably for two reasons. They have been most widely 

 attacked because of their size, and their value is most apparent 

 upon investigation. A number of societies and institutions scat- 

 tered over the continent are actively engaged in studying the 

 economic status of birds. Chief of these are the Kaiserliche 

 Anstalt fiir Land- und Forstwirtshaft zu Berlin, Ornithologische 

 Gesellschaft in Bayern, Paris Museum of Natural History, and 

 the Koniglich Ungarisehe Ornithologische Centrale. The names 

 of Berlepsch, Rey, Custer, Rorig (1903), and HoUrung (1906) 

 have become well known as workers in this field in Germany. 

 Rorig is the one man who has attempted a computation of the 

 comparative amounts of food by a weight method. Csiki (1909) 

 and Greschik (1910, 1911) have been the principal workers in 

 Hungary. Their researches have been mainly confined to the 

 birds of prey. 



