22 
The late Dr. Jenner 
finishes this business in a shorter space of time than any 
other bird, but as he deviates so widely from the common 
laws of the feathered society, I shall select the swift, as a 
better example for pointing out the fact. The swift shows 
himself here about the beginning of May ( sometimes a few 
stragglers appear earlier) and by the beginning of August 
he has completely reared his young ones, which seldom con- 
sist of more than two. At once the old birds and their family 
take their leave and are seen no more for that season. Now 
his farther residence cannot be rendered unpleasant by any 
disagreeable change in the temperature of the air, or from a 
scarcity of bis common food, which at this time abounds in 
the greatest plenty. This circumstance of the early depar- 
ture of the swift, without a more apparent cause, seems to 
have excited much astonishment and perplexity in the mind 
of that attentive and ingenious naturalist, the late Mr. White, 
of Selborne. Speaking of the swift, (Letter XXI. page 184), 
> he says, “ But in nothing are swifts more singular than in 
“ their early retreat. They retire, as to the main body of 
“ them, by the tenth of August, and sometimes a few days 
“ sooner ; and every straggler invariably withdraws by the 
“ twentieth, while their congeners all of them stay till the 
“ beginning of October, many of them all through that 
“ month, and some occasionally to the beginning of Novem- 
“ ber. This early retreat is mysterious and wonderful, since 
“ that time is often the sweetest season of the year. But 
“ what is more extraordinary, they begin to retire still ear- 
“ lier in the most southerly parts of Andalusia, where they 
“ can be no ways influenced by any defect of heat ; or as 
“ one might suppose, defect of food. Are they regulated in 
