176 NATURAL HISTORY OF SELBORNE. 



excepted ; for it is so disposed as to carry " omnes quatuor diyitos 

 anticos" all its four toes forward ; besides the least toe, which 

 should be the back-toe, consists of one bone alone, and the other 

 three only of two apiece. A construction most rare and pecu- 

 liar, but nicely adapted to the purposes in which their feet are 

 employed. This, and some peculiarities Attending the nostrils 

 and under mandible, have induced a discerning naturalist* to 

 suppose that this species might constitute a genus per se.f 



In London a party of swifts frequents the Tower, playing and 

 feeding over the river just below the bridge : others haunt some 

 of the churches of the Borough next the fields; but do not 

 venture, like the house-martin, into the close crowded part of the 

 town. 



The Swedes have bestowed a very pertinent name on this 

 swallow, calling it ring swala, from the perpetual rings or circles 

 that it takes round the scene of its nidification. 



Swifts feed on coleoptera, or small beetles with hard cases over 

 their wings, as well as on the softer insects; but it does not 

 appear how they can procure gravel to grind their food, as swal- 

 lows do, since they never settle on the ground. Young ones, 

 over-run with hippoboscee,l are sometimes found, under their 

 nests, fallen to the ground ; the number of vermin rendering their 

 abode insupportable any longer. They frequent in this village 

 several abject cottages: yet a succession still haunts the same 

 unlikely roofs : a good proof this that the same birds return to 

 the same spots. As they must stoop very low to get up under 

 these humble eaves, cats lie in wait, and sometimes catch them 

 on the wing. 



On the fifth of July, 1775, I again untiled part of a roof over 



* John Antony Scopoli, of Carniola, M.D. 



t The genus cypselus, or swift, is now universally accepted, though at the same time few natu- 

 ralists seem to be aware of the extent to which it differs from hirundo- It is in the skeleton that 

 this diversity is most apparent. The plumage is quite of a different character, and the amazingly 

 thick skin of the swift affords another point of contrast. But it is in the structure and confor- 

 mation of the sternum (that important bone to which the immense pectoral muscles are attached, 

 and upon which, as birds of powerful flight, their whole frame may be said to be especially 

 organized) that the distinctions between these genera are the most remarkable. The vast develop- 

 ment of the sternal ridge in the swift has no counterpart in any of the swallows, which 

 have the sternum much broader and more after the fashion of the dentirostral races ; that of the 

 swifts somewhat resembling those of the true falcons, while the moth-eater again presents an 

 approximation to the more powerfully winged owls. In each, however, the development being 

 greatest in the fissirostral races. The skull is also very different in the swift and swallow genera, 

 in the former being much wider in the gape, and approaching in form to the crania of the 

 moth-eater genus. ED. 



t These insects, which so annoy all the swallow tribes, are now known as the craterina, hirnn- 

 dinit of systematists. Hatched in the nest by the vital warmth of the birds, they live afterwards 

 by sucking their blood. ED. 



