(158 THE NATURAL HISTORY OF SELBORNE. 
roof ; and therefore cannot be so narrowly watched as those 
species that build more openly; but, from what I could ever 
observe, they begin nesting about the middle of May; and I 
have remarked, from eggs taken, that they have sat hard by 
the oth of June. In general they haunt tall buildings, 
churches, and steeples, and breed only in such; yet in this 
village some pairs frequent the lowest and meanest cottages, 
and educate their young under those thatched roofs. We 
remember but one instance where they breed out of build- 
ings, and that is in the sides of a deep chalk-pit near the 
town of Odiham, in this county, where we have seen many 
pairs entering the crevices, and skimming and squeaking 
round the precipices. 
As the swift eats, drinks, and collects materials for its nest, 
on the wing, it appears to live more in the air than any other 
bird, and to perform all functions there save those of sleeping 
and incubation. ; 
This Hirundo differs widely from its congeners in laying in- 
variably but two eggs at a time, which are milk-white, long, 
and peaked at the small end; whereas the other species lay at 
each brood from four to six. It is a most alert bird, rising 
very early, and retiring to roost very late: and is on the wing 
in the height of summer at least sixteen hours. In the longest 
days it does not withdraw to rest till a quarter before nine in 
the evening, being the latest of all day-birds. Just before they 
retire whole groups of them assemble high in the air, and 
squeak, and shoot about with wonderful rapidity. But this 
bird is never so much alive as in sultry thundery weather, 
when it expresses great alacrity, and calls forth all its powers. 
In hot mornings several, getting together in little parties, dash 
round the steeples and churches, squeaking as they go in a 
very clamorous manner; these, by nice observers, are supposed 
to be males serenading their sitting hens; and not without 
reason, since they seldom squeak till they come close to the 
aw Ee 
