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 
