118 NATURAL HISTORY OP SELEOENE. 
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, or engender, frequently 
during the time of building ; and the hen lays from three to five white 
eggs.* 
At first when the young are hatched, and are in a naked and helpless 
condition, the parent birds, with tender assiduity, carry out what comes 
away from their young. Was it not for this affectionate cleanliness the 
nestlings would soon be burnt up, and destroyed in so deep and hollow 
a nest, by their own caustic excrement. In the quadruped creation the 
same neat precaution is made use of; particularly among dogs and cats, 
where the dams lick away what proceeds from their young. But in 
birds there seems to be a particular provision, that the dung of nestlings 
is inveloped in a tough kind of jelly, and therefore is the easier conveyed 
off without soiling or daubing. Yet, as nature is cleanly in all her 
ways, the young perform this office for themselves in a little time by 
thrusting their tails out at the aperture of their nest. As the young 
of small birds presently arrive at their ^At/c/a, or 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 
imperceptible 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 brood ; while the first flight, 
shaken off and rejected by their nurses, congregate in great flocks, and 
are the birds that are seen clustering and hovering on sunny mornings 
and evenings round towers and steeples, and on the roofs of churches 
and houses. These congregatings usually begin to take place about the 
first week in August ; and therefore we may conclude that by that time 
the first flight is pretty well over. The young of this species do not 
quit their abodes altogether ; but the more forward birds get abroad 
some days before the rest. These approaching the eaves of buildings, 
and playing about before them, make people think that several old 
ones attend one nest. They are often capricious in fixing on a nesting- 
place, beginning many edifices, and leaving them unfinished ; but 
when once a nest is completed in a sheltered place, it serves for several 
seasons. Those which breed in a ready finished house get the start in 
hatching of those that build new by ten days or a fortnight. These 
industrious artificers are at their labours in the long days before four in 
* Martins return to the same spot, or some corner of a window ; this has been 
ascertained by direct experiment ; but the nest, the structure of clay, is generally, 
if not always, rebuilt; and the clay, or sometimes almost sand, is rendered 
adhesive by the saliva, or a secretion for the purpose. In their natural habitats 
the nests are placed together frequently in contact, generally on the surface 
of some overhanging cliff. We have seen from fifty to one hundred nests thus 
placed. 
