[ 204 ] 



XXXI. Letter to M. Lacepede, of Farts, on the Natural 

 History of Jsforfh America. Bij Benjamin Smith 

 Barton, M. D. Professor of Materia Medica, Natural 

 History, and Botany, in the University (f Pennsylvania. 



[Concluded from p. 103.] 



OoR coijntn', as you know, is very rich in birds. A 

 considerable nunber of these have been described, or men- 

 tioned, by Bufbn, Pennant, and other writers. But the 

 qrnitholooy of he North American continent is very im- 

 perfectly underlood. Many of our birds have never been 

 correctly, if at all, described. Some of these undescribed 

 species are larse birds ; such as a species of plotus, called 

 in Carolina th^ snake-bird ; not to mention others. But it 

 js a matter of more consequence to study the manners of 

 those birds tha have already been discovered, than merely 

 to detect new ipecies. I flatter nnyself that I have made 

 considerable pogress in the study of the mores of our birds. 

 I have been prticularly attentive to their instincts as we 

 , call them, an; have even digested my collection of facts on 

 this subject iito order. These facts will form a part of a 

 large work onthe Instinct of Animals. It is now com- 

 pletely asccrt.incd that some of the American species of 

 svv-allows renain among us in a torpid state. They retire 

 into the crevces of rocks, into the hollows of trees, and 

 other similar situations, and rest, for some months, in a 

 lethargic sle9 more or less profound. The species con- 

 cerning whici I have the most correct information, as to 

 wliat regardsthcir torpidity, are the purple martin (hirundo 

 purpurea), aid the chimnty-blrd {hirundo pelasgia). Both 

 of these speies, I repeat it, do sometimes become torpid 

 in the climte of Pennsylvania. It is probable that the 

 other specicsdo the same. But I still adhere to my former 

 opinion : I ontcnd that the great body of American swal- 

 lows, ofditlrent species, are really migratory birds ; that 

 is, they leae the climates of the United States on the 

 coming on 'f cold weather, and retire southward, to nriore 

 favourable 1 titudes. These facts show us how much birds 

 can accomnodate themselves to different situations, and 

 give weight to an opinion which I have long entertained, 

 that all aiilaals are capable of the torpid condition. Even 

 the little haiKuing-bird {trochilns colubris), which is im- 

 questionabl- a (generally) migratory bird, is sometimes 

 overtaken ly the colds of our climate, and, on such occa- 

 6ions_, has leen known to fall into the torpid state. 



I lately 



