BIRDS AND NATURE 
17 
concrete instance: the starling is undoubtedly useful in terri- 
tories where animals are being bred on large pastures, for it 
clears the pasture and rids the animals of their parasites, 
but it is equally noxious in districts where there is intense 
cultivation, or where the greatest importance is attached to 
the production of bacciferous fruit. This fact proves again, 
that the feeding of birds may change with the season and 
surroundings or with opportunities: e. g. certain breeds of 
gulls, which by their mode of life are bound to water, appear 
on dry land when locusts or grasshoppers are plentiful, and 
hunt for them as long as the supply lasts. 
Here mention must be made of a deficiency still extant 
in our knowledge of birds, i. e. that even today we have 
practically no detailed knowledge concerning the food of 
birds. 
Inquiries in this direction were begun in the first year 
of the XX century, but have been carried on only spor- 
adically.^ 
The fact that the relation of birds to territory is so very 
diverse has always rendered and still renders extremely diffi- 
cult any international agreement as to the classification of 
birds to be protected and those to be extirpated, i. e. useful 
and noxious birds, treated by species; in fact it has often made 
such an agreement impossible seeing that our knowledge on 
certain points, e. g. concerning the question of food, is very 
deficient. In this field there is much that is uncertain, sup- 
positional or traditional, a fact which renders the formation 
^ At the Fourth International Ornithological Congress held in Lon- 
don in 1905, Hungary was the only country that could produce any 
results in this field. Inquiries are being made in Germany and Belgium. 
The task is a very difficult one, but the solving of the problem is im- 
portant, as it will throw extraordinary light on the significance of birds. 
H erman: Conv. for the Prot. of Birds. 2 
