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, a-e led by choice to feed on carrion, or dead animal matter. 
Birds, besides, ::re 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 times, 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 
secure his crop. 
Jam veris prenuncia venit hirundo. — Ovid. 
Now comes the swallow, harbinger of spring. 
Tum cornix plena plurium vocat mproba voce.—Virg. 
The crow with clamcrous 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, 
