APPENDIX. 371 



'^ The Swif t^ Hirundo apus, is the latest in its Visit, usually 

 appearing first in May, and not continuing with us nearly 

 so long as its Congeners ; the latest that I ever saw it was 

 the 11th of August. 



'^ How this Tribe of Birds dispose of themselves in Winter ? 

 is a Question that has employed the Pens of the most able 

 Naturalists, some of whom assert that they migrate from 

 one Country to another, and others that they dispose of 

 themselves in Holes and Caverns, and even under Water, 

 remaining in a torpid State till the Return of Spring, and 

 then survive and resort to their old Haunts : both of which 

 opinions have been so ably supported by Authors of the 

 first Credit, that it is scarcely possible to refuse one's Assent 

 to each of them ; and indeed (tho' it may be thought pre- 

 sumptuous in me to hazard a Conjecture after such great 

 Authorities) I am inclined to think that what that very able 

 Naturalist Mr. Pennant asserts is tha real Fact, that the 

 greatest Part of this Tribe do migrate, but that some of 

 them, perhaps the late Broods and weak Birds, have a Power 

 of laying themselves up during Winter in Holes and Caverns, 

 in a torpid State, and of reviving again in the Spring at the 

 same Time wdth the Flies and other Insects ; for why should 

 not the Bird be capable of doing this as well as the Insect 

 on which it feeds ? Of their Migration I think 1 have often 

 observed what amounted to almost a Proof of it, viz., their 

 assembling together in great Numbers (1 mean only Swal- 

 lows and Martins, H. rustica and urhica) on the Tops of 

 Buildings, in the Month of September, and sometimes great 

 Flights of them are seen very high in the Air ; indeed from 

 the Testimony of Sir Charles Wager and Capt. W^right 

 there can be no Doubt of it : and some Circumstances have 

 induced me to give Credit to the Opinion of (at least some 

 of them) passing the Winter in a Torpid State. So late as 

 November, long after the Majority of them have disappeared, 

 1 have frequently observed, on a warmer Day than usual, 

 one or two Swallows or Martins flying backwards and 



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