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for its family. The crust or shell of this nest seems to 

 be formed of such dirt or loam as comes most readily to 

 hand, and is tempered and wrought together with little 

 bits of broken straws to render it tough and tenacious. 

 As this bird often builds against a perpendicular wall 

 without any projecting ledge under, it requires its utmost 

 efforts to get the first foundation firmly fixed, so that it 

 may safely carry the superstructure. On this occasion 

 the bird not only clings with its claws, but partly supports 

 itself by strongly inclining its tail against the wall, making 

 that a fulcrum; and thus steadied it works and plasters 

 the materials into the face of the brick or stone. But 

 then, that this work may not, while it is soft and green, 

 pull itself down by its own weight, the provident architect 

 has prudence and forbearance enough not to advance her 

 work too fast ; but by building only in the morning, and 

 by dedicating the rest of the day to food and amusement, 

 gives 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 an hemi- 

 spheric 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 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 



