( vii ) 
jecture: but it is a conjecture which derives support from many interesting facts which I have collected and which 
wiU be mentioned and explained in my Geographical View of the Trees and Shrubs of North-America. In that work 
I shaU show, that the southern trees and shrubs (that is, those vegetables which attain to their greatest perfection in 
the southern chmates of our continent, particularly of the United-States) are, in general, found much farther 
north m the western than they are in the eastern parts of our country. This fact seems to show, and the point is 
put beyond any manner of doubt, by thermometrical observations, that the western climate, in the same lati- 
tudes, IS more temperate than the eastern. Of course, it were natural to suppose, that the southern birds to whom 
heat IS so gemal, would often be sohcited farther north in the western than in the eastern district. This with respect 
to some birds, is actually the case. Mr. Jefferson has observed, that ^^Perroquets even winter on the Sioto in the 
39th degi-ee of latitude." * I have certain information, that these birds winter still farther north than is here mentioned. 
§. IX. 
Birds, in migrating, are fond of following the courses of rivers, and other large streams of water. This circum- 
;iance, m my opmion, partly explains the reason, why some of the birds of the southern parts of the United-States 
md also some of the South-American birds, which have never, or very rarely, been discovered in the Atlantic coun- 
nes of Nortt-America, are not uncommon in the countries west of the AUeghaney-Mountains. These southern 
nrds, following the courses of the Mississippi, and its branches (the Ohio, the Illinois, &c.) are spread or dispersed 
trough the rich and extensive territories that are washed by these waters. Whether or not this explanation be 
-dmitted, the fact is certainly as I have stated ; and to the naturalist it cannot but appear interesting. The Psittacus 
.ertmax is one of the birds of Brazil; and the Muscicapa Tyrannus, which is held in so much esteem by the Nau- 
lowessies, and other western Indian tribes, is a native of Surinam, and of the country bordering on the river Plata 
It IS, I think, m general, a just observation, that our Spring and Summer birds of passage continue with us 
bout six months, and are absent for the same length of time. Accordingly, those birds which arrive early in the 
prmg disappear early in the autumn, and those which arrive late in the spring do not disappear untU late in the au- 
amn. Our late springs are commonly succeeded by late and warm autumns, which, by keeping aHve the numerous 
pecies of msects, which are the favourite food of ahnost aU our summer birds of passage, detain these birds for a 
onsiderable time among us. 
§.XL 
The greater number of the Spring and Summer birds of passage, which I have mentioned, build and breed in 
emi8ylvama.t Perhaps, they all breed in some part of this extensive state, with the exception of the Vultur 
ura (Turkey-Buzzard), and a few others, which do not visit us until towards the close of the summer. It has lately 
3en ascertained, that the Ampelis Garrulus, or Prib -Chatterer (Cedar-Bird) does breed in Pennsylvania; and I 
)ubt not, that the same wHl, in time, be discovered to be the case with the Emberiza Oryzivora (Rice-Bird, 
eed-Bird), and others whose nests have not hitherto been seen in Pennsylvania. It is not unhkelv, however, that 
me of these birds of passage continue their migration farther northward, to New-York, New-England, Vermont, 
3. and there breed and raise their young, returning southward, through Pennsylvania, in the faU. 
§. XIL 
It is an interesting fact, for which we are indebted to Mr. William Bartram, that very few of our bii-ds of passage 
>ni the south "build or rear their young in the south or maritime parts of Virginia and CaroUua, Georgia and 
Notes on the state of Virginia. Page 139. The original edition. 
See Appendix I. where I have designated with an asterisk (*) those birds which are known to breed in Pennsylvania. The greater number of them 
8 marked breed within a few miles of PhUadelphia. 
I 
