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OCCASIONAL, OR ACCIDENTAL, RESIDENTS. 
There is a propriety in the division of the Resident Birds, into snch as commonly continue in the country the whole 
year through, and such as only occasionally continue. The latter may he called Occasional, or Accidental 
Residents. They seldom continue with us except in open, mild winters. These, in the preceding list, are 
marked with an a^.terisk.* I have had the less hesitation in blending them together, because it is highly probable, 
that m a tract of country so extensive and various as the state of Pennsylvania, some of the birds, which about 
Philadelphia are only occasionally resident, may be more generally so in other parts of the country. 
OCCASIONAL VISITANTS. 
Some of the birds which are observed in Pennsylvania may, with propriety, be thrown into a section called Occa- 
sional Visitants. Of these I have already made mention in the Introduction to these Fragments. These 
Occasional Visitants are such birds as occasionally come to Pennsylvania, either from the more northern or from 
the more southern parts of North-America. With all the causes which induce them to visit us, I am not suffici- 
ently acquamted to speak on the subject, with confidence. The following, however, are certainly some of the>e 
causes, viz. severity of cold, scarcity of food, and intensity of heat. 
I. The birds which are driven by the severity of cold all come to us from the northward. These occasional visit- 
ants are pretty numerous, during our very severe winters, when some of the birds of Canada and Labrador are 
seen among us. The two following species of Strix deserve to be mentioned under this head, viz. the Great 
White Owl (Strix Nyctea.?). This species is never seen in the vicinity of Philadelphia, except in those winters 
which are very severe, long, and close. This and the following species (See the Tables) were seen about Phila- 
delphia, at the close of the winter of 1791-92, which was one of our severest winters. The Tawney-Faced 
Owl (Strix stridula ?) is a very beautiful species. It makes its appearance, in the day-time, near houses and barns, 
watching for mice, or for those weakly birds which have been compelled by the severity of the cold to take shelter 
there, 
[I. It may readily be imagined, that a scarcity of food, particularly of their favourite food, is one of the causes 
which mduce birds to make occasional visits to other countries than their own. I am even of opinion, that this 
has been the original cause of some of those migrations which are now regular and extensive. 
II. ^ I have mentioned intensity of heat, or very warm weather, as one of the causes which sometimes impel or induce 
birds to migrate to us. It is probable, however, that this cause more frequently operates in a secondarv manner ; 
that IS, by producing a scarcity of food. All the Occasional Visitants that fall under this section comj from the 
southward. See the Introduction, where I have mentioned some of these visitants. 
ADDITIONS TO THE LIST of BIRDS. 
he following deserve a place in an history of the birds of Pennsylvania. They are all, except the Psittacus, found 
m the vicmity of Philadelphia, or within eighty miles of it. 
ACCIPITRES. 
Falco Ossifragus ? Sea-Eagle. I mention this on the authority of my ingenious friend Mr. G. S. Oppelt, of 
Nazareth, in Pennsylvania. He says it agrees with the Falco Ossifragus, " only that the cera is not lutea but 
obscura." The one which he examined measured seven feet from wing to wing. Killed near Nazareth. MS. 
Strix Aluco. Speckled Owl. On the authority of Mr. Oppelt. 
Strix Naevia. Mottled Owl. On the authority of Mr. Oppelt. 
Strix passerina. Little Owl. 
PIC^. 
I Psittacus pertinax ? Illinois Parrot ? Either this or some other species of the genus deserves to be mentioned 
among the birds of Pennsylvania. It has been seen in Shareman's Vallev. See Introduction, §. VII. 
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