4 ANIMAL ARTISANS 



to it along the side of the wall. This suggests that 

 in former ages the ideal place for a martin's nest was 

 not under the eaves, but at the end of a hole, and 

 that the tunnel attached to the wall is a kind of 

 reminiscence of this. In the same way, probably the 

 black wheatear's ideal location is a very narrow crack 

 in a rock-face. Failing this, the barrier is built up 

 in front in order to improve the environment, for it 

 has no necessary result in improving the nest itself. 

 The pebble foundations belong to a different order of 

 ideas. Foundations of masonry of one kind or another 

 are quite common, even among English birds. The 

 ringed plover, which practically makes no nest, always 

 lays a foundation of broken shells or little stones, 

 on which the four eggs are placed. It commonly 

 scatters a few broken shells round it too, even if the 

 nest is made upon the grass or on sand. The black- 

 bird and the magpie, as well as the carrion-crow, 

 sometimes build foundations of mud, which hardens 

 into a kind of mortar, for their nests, the blackbird 

 also working this mud into a cup, which is subsequently 

 lined. The material is usually taken from the nearest 

 ditch. The thrush, on the other hand, makes a very 

 careful " compost " of cow-dung and rotten wood, 

 smooths this into a perfect bowl, and lays its eggs 

 directly on this extremely clean, hard, and light 

 lining. The only drawback to this and to the mud 

 nests is that the rain soon softens them, though the 

 thrush's compost lasts the longer. Both birds seem 

 to understand the art of mixing their building material 

 into a uniform substance. The swallows and house- 





