70 THE LIFE OF A BIRD. 



so carrying deeper its tunnel. The other bird all 

 the while appears to cheer the labourer, and urge 

 it to continue its exertions, and, when the latter 

 is fatigued, takes its place. Thus, by the co- 

 operation of both, the hole is dug to the as- 

 tonishing depth of four, five, or even six feet in a 

 horizontal direction! The hole is just large 

 enough to admit the passage of a single bird at a 

 time: at its extremity is an oven-shaped cavity, 

 in which the eggs are deposited. Audubon put 

 the mining powers of this little bird to a severe 

 trial. A small net bag was fastened over the 

 entrance hole, the bird being known to have gone 

 into its nest, but before morning it had made its 

 escape by scratching away the earth under the 

 net. The next time, a stick that filled the 

 entrance was driven into it to the depth of a foot, 

 but again unsuccessfully, for by the next day the 

 bird had worked its way out. 



In the case of the woodpeckers, both birds also 

 co-operate in the excavation. The strength of 

 the bill of some species is very great. Audubon 

 says, "I have seen the ivory-billed woodpecker 

 detach pieces of bark seven or eight inches in 

 length at a single blow of its powerful bill ; and, by 



