410 AVES. 



infinitely more prejudicial multiplication of creatures, still more destructive. 

 Some families of birds destroy field mice, snakes, frogs, and lizards; and 

 others again, are led by choice to feed on carrion, or dead animal matter. 

 Birds, besides, are extensive agents in the spread of vegetables and even 

 animals. It is well ascertained that wild ducks, in their emigrations, carry 

 impregnated spawn into remote ponds, and thus stock them with fish ; and 

 many by swallowing seeds whole, and subsequently expelling them, are the 

 means of spreading vegetation over an extent of surface which scarcely 

 any other means could accomplish. A great portion of this class and 

 their eggs may be used as food ; and the feathers of many, form an object 

 of commerce. 



Nothing is more singular in the history of birds, than their periodical 

 migrations. That these are connected in some measure with the necessity 

 of a supply of food, and the impulse of reproduction, is almost demonstrated; 

 but the instinctive feeling which guides them, without compass, across seas 

 and continents, and enables them to migrate at certain periods, correspond- 

 ing with the production of their food in distant countries, can only be 

 referred to one Great Source. 



, Who bade the stork, Columbus-like, explore 



Heavens not his own, and worlds unknown before ? 

 Who calls the council, states the certain day ? 

 Who forms the phalanx, and who points the way? 



The flights of migratory birds have been noticed from the earliest periods ; 

 " the stork in the heaven knoweth her appointed limes, and the turtle, and 

 the crane, and the swallow observe the time of their coming." And, as 

 if their passage through the air, or the structure of their bodies made them 

 sooner perceive the incipient changes of the weather, the appearance and 

 cries of birds have long been considered to afford presages of the coming 

 storm, or the cessation of the tempest. The institution of a college of 

 Augurs, at Rome, may therefore be conceived to have reference to something 

 better than mere superstition; and though the flight of particular species 

 might, in the hands of interested individuals, be made to presage the wished 

 for result of a battle, or direct a march already determined on, yet, in the 

 absence of the barometer and thermometer, the appearance or disappearance 

 and cries of birds, were the signals for the husbandman to sow his fields, or 

 to secure his crop. 



Jam veris prosnuncia venit hirundo. — Ovid. 

 Now comes the swallow, harbinger of spring. 



Tum comix plena plurmm vocat improba voce. — T'iVg'. 



The crow with clamorous cries the shower demands. — Dryd. 



In this country, the great migrations of birds take place in spring and 

 autumn. Those which arrive in spring, come from warmer climates, and, 



