OBSERVATIONS ON BIRDS. 397 



Here, and in many other passages of his writings, this very 

 ingenious naturalist savours the opinion that part at least of the 

 swallow tribe pass their winter in a torpid state in the same manner 

 as bats and flies, and revive again on the approach of spring. 



I have frequently taken notice of all these circumstances, which 

 induced Mr. White to suppose that some of these hirundines lie 

 torpid during winter. I have seen so late as November, on a finer 

 day than usual at that season of the year, two or three swallows 

 flying backwards and forwards under a warm hedge, or on the 

 sunny side of some old building ; nay, I once saw on the 8th of 

 December two martins flying about very briskly, the weather being 

 mild. I had not seen any considerable number either of swallows 

 or martins fora considerable time before ; from whence then, could 

 these few birds come, if not from some hole or cavern where they had 

 laid themselves up for the winter? Surely it will not be asserted 

 that these birds migrate back again from some distant tropical 

 region merely on the appearance of a fine day or two at this late 

 season of the year. Again, very early in the spring, and sometimes 

 immediately after very cold severe weather, on its growing a little 

 warmer, a few of these birds suddenly make their appearance, long 

 before the generality of them are seen. These appearances cer- 

 tainly favour the opinion of their passing the winter in a torpid 

 state, but do not absolutely prove the fact ; for who ever saw them 

 reviving of their own accord from their torpid state, without being 

 first brought to the fire, and as it were forced into life again ? soon 

 after which revivification they constantly die. MARKWICK. 



SWALLOWS, CONGREGATING AND DISAPPEAR- 

 ANCE OF. 



During the severe winds that often prevail late in the spring it 

 is not easy to say how the hirundines subsist; for they withdraw 

 themselves, and are hardly ever seen, nor do any insects appear 

 for their support. That they can retire to rest and sleep away 

 these uncomfortable periods, as bats do, is a matter rather to be 

 suspected than proved ; or do they not rather spend their time in 

 deep and sheltered vales near waters, where insects are more likely 

 to be found ? Certain it is, that hardly any individuals of this 

 genus have at such times been seen for several days together. 



September 13, 1791. The congregating flocks of hirundines on 



