250 NATURAL HISTORY 



winter. About the middle of May, if the weather be 

 fine, the martin begins to think in earnest of providing 

 a mansion 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 superstruc- 

 ture. On this occasion the bird not only clings with 

 its claws, but partly supports itself by strongly inclin- 

 ing 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 enoifgh not to advance her work too 

 fast ; but by building only in the morning, and by dedi- 

 cating 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 hemis- 

 pheric nest with a small aperture towards the top, strong, 

 compact, and warm; and perfectly fitted for all the pur- 

 poses 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 man- 

 sion, 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 



