302 FIELD, FOREST AND FARM 



open-air chase : they pursue their game on the wing, 

 hunting for gnats, moths, mosquitoes, and flying 

 beetles. They must have a short beak, but one that 

 opens wide and snaps up unerringly insects on the 

 wing, despite the uncertainties of aerial flight; a 

 beak in which the victim is caught and held without 

 any retardation of the bird's swift course; in short, 

 a beak with a sticky lining which a tiny butterfly 

 cannot so much as graze with its wing and not be- 

 come entangled. Above all, an untiring and swift 

 wing is necessary, one that does not flag in the pur- 

 suit of game desperately putting forth its utmost 

 efforts to escape, and one that is not baffled by the 

 tortuous course of a moth driven to bay. A beak 

 inordinately cleft and wings of extraordinary power 

 — such, in a word, should be the equipment of the 

 bird whose hunting ground is the vast expanse of 

 the open air. 



"These conditions are fulfilled in the highest de- 

 gree in the swallow and the martin, both of which 

 hunt flying insects, pursuing them this way and that, 

 back and forth, ceaselessly and with a thousand sub- 

 tle tricks. They catch them in their wide-open and 

 viscous gullet, and continue their course without a 

 moment's pause. 



"The bird that lives on grain and seeds, the gra- 

 nivorous bird, as it is called, has a beak that is very 

 wide at the base and adapted by its strength to the 

 opening of the hardest seeds. In this class are the 

 chaffinch, the greenfinch, the linnet, the goldfinch, 

 and the swallow. The bird that lives on insects, or 



