( xiv ) 
same rout. This migration of tlie bears is particularly observed at Manchac, on the Mississippi, about the latitude of 
. Many other quadrupeds perform similar migrations, both in the old and in the new world. i 
§.xxx. ^ i 
Nothing seems more improbable than that a class of animals, such as the greater number of birds, which are ca- 
pable of rapid and immense flights, should continue in a country in which the winter's cold is generally very intense, 
and in which, at the same time, the principal articles of their food are not to be procured. But I am far from deny- 
ing, that some birds do pass their winters with us, either in a torpid state, or otherwise. Some species continue with 
us pretty regularly: and individuals of many species do occasionally continue with us. I have already observed, 
that "during our mild winters, several of those species of birds which, in general, are undoubtedly migratory, 
continue the winter through in the neighbourhood of Philadelphia."* It must be evident, therefore, that extreme 
cold is the great cause which compels these animals to retire south. But it is not the only cause. A deficiency of 
their proper food is another, not much less extensive. The greater number of our birds of the order of passeres 
feed upon insects, and the seeds and berries of vegetables. These, particularly the former, are not to be procured 
in the winter-season, in quantity suflicient to answer the demands of the immense number of birds which visit us at 
other seasons of the year. If our climate were more moderate than it is, and if an abundance of food were at 
all times to be procured, the number of our Resident Birds would, doubtless, be much greater than it is. It is 
evident, that a failure of their food is one of the great causes of the migrations of birds. Thus no sooner has the 
Zizania aquatica (Reed), which is one of the principal foods of the Rice-Birds, shed its seed, than these birds disap- 
pear, returning southwards, f 
§. XXXI. 
Independent on the mildness of the season, and the continuance of an abundance of their favourite kinds of food, 
individuals (and in some instances large flocks) of many diflerent kinds of migratory birds pass their winters with us. 
Dr. Darwin observes, that " those swallows that have been hatched too late in the year to acquire their full 
strength of pinion, or that have been maimed by accident or disease, have been frequently found in the hollows of 
rocks on the sea coasts, and even under water in " a " torpid state, from which they have been revived by the warmth 
of a fire." J I suppose the learned doctor has not completely ascertained the fact, that such swallows were actually 
hatched later than others, or that they had been maimed by accident or disease. But it is highly probable, that the 
circumstances which he mentions are some of the causes which compel these and many other kinds of birds to pass their 
winters in climates, and in situations, very different from those in which the species at large, are, at such times, found. 
§. XXXII. 
Birds, in migrating, often lose themselves, particularly, perhaps, when they get into the currents of strong winds, 
to which they must sometimes be obedient. The large flight of Parakeets, § which visited the neighbourhood of Al- 
bany, in the winter of 1780, was no doubt carried thither by a strong westerly wind. Such wanderers, it is pro- 
bable, often go into a torpid state. It is said, that great numbers of Parakeets (I suppose Ihe Psittacus carolinensis) 
are sometimes, in the winter-season, found torpid in the hollows of trees, in North-Carolina. Admitting 
the fact, is it not likely, that these birds have been wanderers, like the New-York flock just mentioned ? Accidents 
of this kind are more frequent than is perhaps imagined. And I do not doubt that to such accidents we must ascribe 
some of the instances of swallows and other birds being found, in the winter-season, in a state of hybernation. II , 
will be said, that tliis idea favours the notion, that birds are capable of entering into this state according to theiil I 
situation, 1 do really suppose so. Perhaps all birds, all quadrupeds, in short all animals, are capable of this state. Noi! 
are vegetables exempted from it. Those aquatic plants which, at the approach of winter, withdraw themselves to the ■ 
bottom of the water, and, on the opening of the spring, emerge from their watery bed, may be denominated Hyber-, 
* See page iz. ^. XVI. 
t See the Tables. Page 8. 
I Zoonomia, Vujl. I. Sect. XVI. 
^ See Page vi. §. VII. 
