NATURAL FI I STORY OF SELBORNE. 153 



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 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 aflfectionate 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 nest- 

 lings 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 of the aperture of their nest. As the young of small 

 birds presently arrive at their ijXiKia, or full growth, they 

 soon become impatient of confinement, and sit all day with 



