The Food of Birds. 631 



But as all these branches of cultivation vary with the 

 seasons, it is obvious that the examination of the food of 

 birds must closely follow the different steps in the yearly 

 course of these industries. 



We must examine the food taken by every single species 

 during a particular season, and then, in order to obtain a 

 clear idea of the usefulness or harmfulness of a certain 

 species^ calculate the benefit or harm the species has caused 

 to an individual branch of industry during a certain period. 



Such, iu its general outlines, is the method to be followed 

 and, so far, it presents no insuperable difficulties. 



Complications and difficulties arise, however, from the fact 

 that an individual species may be considered useful in one 

 country and harmful in another, according to the more or 

 less pronounced divergency of interests prevailing in the 

 different countries. 



For example, it took nearly three decades, before an inter- 

 national convention concerning the protection of birds useful 

 to agriculture, could be signed and a list of useful and harm- 

 ful birds drawn up. 



The question itself as to what food birds eat, is somewhat 

 difficult of solution. First of all, many thousands of birds 

 have to be observed, throughout the entire year in the case 

 of permanent inhabitants, and in the case of migrating birds, 

 during the time of their stay with us. 



The data relating to their modes of life have to be recorded, 

 the contents of stomach and crop have to be taken out, 

 preserved, sorted and analysed by the aid of the microscope, 

 and finally the number of individuals stated. In most cases 

 there are only fragments of insects by means of which any 

 determination can be made. Moreover, the results obtained 

 by the examination of one individual furnish no rule. 



To establish the characteristic features of a species, the 

 examination of a large number of individuals is necessary, 

 and how can these be obtained without the slaughter of 

 innumerable birds ? 



I pass now to the work of the Hungarian Central Office for 

 Ornithology. 



Hungary did not wait for the decisions of the Congress of 

 Paris, because the Government had already provided gene- 



