( ix ) 



other circumstances will greatly regulate the arrival of birds in, and their flight or removal from, a particular 

 country. Sometimes, there is a diflerence of three weeks or a month between the an-ival, or appearance, of the 

 same species, in two different years. This will appear from the following instances, which are selected from many 

 others. 



§■ XV. 



From an inspection of these Tables, it will appear, that the Alauda alpestris, or Shore-Lark, the Alauda rubra, 

 or Ked-Lark, the Fringilla tristis, or Golden Finch, and some others, were not observed, in the vicinity of Pliila- 

 delphia, earlier than the twelfth of March, 1791 : whereas the same birds were seen, in the same neighbourhood, as 

 early as the twenty-eighth of February, the following year, on their passage northward. 



I have placed the Anas canadensis (Wild-Goose) between the 15th and the i8th of April, i79i,but in the year 

 1794., these birds were observed, on their migration from the south, as early as the 3d of March. In the first men- 

 tioned year the Ardea Herodias, or Great Heron, was not observed before the 1 5th or 1 6th of April ; but in the 

 latter year, numbers of these birds were seen as early as the ist of April. Many other instances might be mentioned. 



§. XVI. 



How much the movements of birds from one country to another depend upon the state of the seasons, will ap- 

 pear from different parts of this little work ; particularly from the Third Section. Here we find, 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. Such, which I have denominated the Occasional, or Acci- 

 dental, Resldbnt Biebs, are the Ardea Herodias, or Great Heron, Columba carolinensis, or Tiu'tle-Dove, the 

 Fringilla melodia, and several others: I doubt not many more than I have mentioned. The Columba migi'atoria, 

 Passenger-Pigeon, commonly returns from the northward late in the fall, and continues with us a few days, or 

 weeks, feeding in our fields upon the seed of the buclrwheat,* or in the woods upon acorns. But if the season be 

 a very mild one, they continue with us for a much longer time. This was the case in the winter of 1792 — 1793> 

 when immense flocks of these birds continued about the city, and did not migrate farther southward, until the weather 

 became more severe in the month of January. The winter of 1792 — 1793, was one of the mildest that had ever 

 been remembered in Pennsylvania. It is a common observation in some parts of this state, that when the Pi- 

 geons continue with us aU the winter, we shall have a sickly summer and autumn. There is, perhaps, some foun- 

 dation for this notion. Large bodies t of these birds seldom do winter among us miless the winter be very mild ; and 

 the experience of some years has taught us, that such winters are often followed by malignant epidemics. The mild 

 winter of 1792 — 1793, was succeeded by a dreadful malignant fever, which destroyed between four and five thousand 

 people in Philadelphia; and I am assured, that the same fever in 1762 was preceded by an extremely open winter, 

 during which the pigeons remained about Philadelphia, and in other parts of the state. In the hands of a poet, a 

 Lucretius, or a Virgil, this coincidence between the accidental hiemation of the pigeons and tlie appearance of tlie 

 yellow-fever might be wrought up into a system of beautiful extravagance. 



§. XVII. 



If birds, in their migration from one country to another, were impelled by a " determinate," or necessary instinct, 

 the periods of their ari'ival and departure would be more uniform and flxed. But we have seen, that there is a 

 considerable diflerence in these respects, even in two years immediately in succession. Such great regularity in the 

 migrations of these animals by no means accords with those accommodating habits, which the naturalist discovers in 

 his investigation of the manners of all animals ; those habits which have been given to them, as to us, by a Cre- 



* Polygonum Fagopyrum. t I say " large bodies," for I believe individuala of these birds continue with ua almost every winter. 



