( xiv ) 



same rout. This raigratiou of the bears is particularly observed at Manehac, on the Mississippi, about the latitude of 

 . Many other quadrupeds perform similar nii^Tatious, both in the old and in the new world. 



§. XXX. 



Nothing seems more improbable than that a class of auimals, 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 -n'hich, 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 migi-atory, 

 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 luimber of our birds of the order of passeres 

 feed upon insects, and the seeds and berries of -\-egetables. These, particularly the former, are not to be procured 

 in the -winter-season, in quantity sufficient 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 Kesident Birds would, doubtless, be much gi-eater 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 

 Zizauia aquatica (Reed), which is one of the principal foods of the Rice-Birds, shed its seed, than these birds disap- 

 pear, returning southwards, t 



§. 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 different 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 foimd 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 tire." % I suppose the learned doctor has not completely ascertained the fact, that such swallo-n-s 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. 



,V XXXII. 



Birds, in migrating, often lose themselves, particidarly, perhaps, when they get into the current.? 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 the Psittacus carolinensis) 

 are sometimes, in the winter-season, found toi-pid 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. It 

 will be said, that this idea favours the notion, that bu-ds are capable of entering into this state according to their 

 situation, 1 do really suppose so. Periiaps all birds, all quadrupeds, in short all animals, are capable of this state. Nor 

 aro vegetables exempted from it. Those aquatic plants which, at the approach of winter, withdraw themselves to the 

 liottom of the water, and, on the opening of the spring, emerge from tlnir watery bed, may be denominated IIvnKn- 



' See page ii. 5. XVI. t See tht TaMcs. I'ugc 8. I Zoonumia, V.ii.. I. Sect. XVI. 5 See I'age vi. 5. VIl. 



