166 THE NATURAL HISTORY 



the dawn of day they always revisit their nest-trees, and 

 are preceded a few minutes by a flight of daws, that act, as 

 it were, as their harbingers. 



I am, etc. 



LETTER XVni 



SELnoRNE, Jan. 29, 177'1. 



Dear Sir, 



The house-swallow, or chimney-swallow, is undoubtedly 

 the first comer of all the British hirundines ; and appears 

 in general on or about the thirteenth of April, as I have 

 remarked from many years' observation. Not but now 

 and then a straggler is seen much earlier : and, in par- 

 ticular, when I was a boy I observed a swallow for a whole 

 day together on a sunny warm Shrove Tuesday ; which 

 day could not fall out later than the middle of March, and 

 often happened early in February. 



It is worth remarking that these birds are seen first about 

 lakes and mill-ponds ; and it is also very particular, that 

 if these early visitors happen to find frost and snow, as 

 was the case of the two dreadful springs of 1770 and 1771, 

 they immediately withdraw for a time. A circumstance 

 this much more in favour of hiding than migration ; since 

 it is much more probable that a bird should retire to its 

 hybernaculum just at hand, than return for a week or two 

 only to warmer latitudes. 



The swallow, though called the chimney-swallow, by no 

 means builds altogether in chimneys, but often within 

 barns and out-houses against the rafters ; and so she did 

 in Virgil's time : 



. . . . " Aiit6 

 Garrula quam tignis nidos suspcndat hirundo." 



