i 
THE NATURAL HISTORY OF SELBORNE. ey 
it sufficient time to dry and harden. About half an inch seems 
to be a sufficient layer for a day. Thus careful workmen, 
when they build mud-walls (informed at first perhaps by this 
little bird), raise but a moderate layer at a time, and then 
desist, lest the work should become top-heavy, and so be 
ruined by its own weight. By this method in about ten or 
twelve days is formed a hemispheric nest with a small aperture 
towards the top, strong, compact, and warm, and perfectly 
fitted for all the purposes for which it was intended. But 
then nothing is more common than for the house-sparrow, as 
soon as the shell is finished, to seize on it as its own, to eject 
the owner, and to line it after its own manner. 
After so much labor is bestowed in erecting a mansion, as 
Nature seldom works in vain, martins will breed on for several 
years together in the same nest, where it happens to be well 
' sheltered and secure from the injuries of weather. ‘The shell 
or crust of the nest is a sort of rustic work, full of knobs and 
protuberances on the outside ; nor is the inside of those that 
I have examined smoothed with any exactness at all; but is 
rendered soft and warm, and fit for incubation, by a lining of 
small straws, grasses, and feathers, and sometimes by a bed of 
moss interwoven with wool. In this nest they tread frequently 
during the time of building; and the hen lays from three to 
five white eggs. 
As the young of small birds presently arrive at their full 
growth, they soon become impatient of confinement, and sit 
all day with their heads out at the orifice, where the dams, by 
clinging to the nest, supply them with food from morning to 
night. For a time the young are fed on the wing by their 
parents; but the feat is done by so quick and almost imper- 
ceptible a flight that a person must have attended very exactly 
to their motions before he would be able to perceive it. As 
soon as the young are able to shift for themselves, the dams 
immediately turn their thoughts to the business of a second 
