158 NA TURAL HISTOR Y OF SELBORNE. 



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 an 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 commoji 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 labour 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, 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 

 enveloped 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 77X1*10, or full 

 growth, they soon become impatient of confinement, and sit all 



* Martins return to the same spot, or some c irner of a window ; this has been ascer- 

 tained by direct experiment ; but the nest, the structure of clay, is generally, if n >t 

 always, rebuilt ; and the clay, or sometimes almost sand, is rendered adhesive by the 

 saliva, or a secretion f.>r the purpose. In their natural habitats the nests are placed 

 together frequently in contact, generally on the surface of some over-hanging cliff. We 

 have seen from fifty to one hundred nests thus placed. 



