4 The Wilson Bulletin. 



expedient, viz.: to wall up the entrance to his nest, reduc- 

 ing it to a small hole, just large enough for him to slip in 

 and out of. 'This,' reports my father, 'is done with clay 

 or other viscuous earth which, as in the nests of swallows, 

 is moistened, bound and held together with a glutinous 

 saliva. The walling up of the nest cavity soon comes to an 

 end, as he carries lump after lump of clay in his bill, moist- 

 ens it all over, and sticks it fast in its place. It is just as if 

 a little mason, to lock or obstruct a door, was laying in and 

 making fast one stone after another.' 



"This clay wall is two and more centimeters in thickness, 

 and when dry is so firm that it cannot be broken out with 

 the finger, but a chisel must be used if one would burst it. 

 The entrance hole, which is always in the middle of the 

 wall, is circular, and so narrow that a Nuthatch can scarcely 

 creep through. Once let the nest be finished, it is safe from 

 all animal marauders. Only the woodpeckers have the abil- 

 ity to demolish it, and they do so when the nest-hole has 

 been taken from them by a Nuthatch." 



The only parallel habit in the American Nuthatches — if, 

 indeed, it is to be compared with mud-daubing — is that of 

 the Red-bellied Nuthatch, who puts a patch of pine turpen- 

 tine above and below his nest-hole. The nests of the Euro- 

 pean Nuthatch found, as quoted above, regularly in tree 

 cavities, sometimes in rock-crannies, grade naturally into 

 those of the rock-nesting species; but the latter are the bet- 

 ter developed — completely so, in fact, for there is apparently 

 no room for improvement. Whether the tree-nesting spe- 

 cies have degenerated from the perfected clay workers, or only 

 indicate the path along which the latter reached their pres- 

 ent habits, is a question that is interesting, and very possi- 

 bly might be answered by those who have more data than 

 the writer. The natural supposition is that the nuthatches 

 are originally birds of the woods, and that where timber was 

 scarce some took to life on the rocky ledges, there learning 

 gradually to build the form of nest best adapted to their en- 

 vironment. 



