114 BIRDS' NESTS 



hidden under heaps of loose stones and rocks, or in 

 crevices of the latter. For such a situation it is 

 exceptionally bulky, being cup-shaped, and made 

 externally of dry grass, moss, and roots, and warmly 

 lined with finer fibres, hair, wool, and feathers. No 

 doubt in prehistoric ages this was the Snow Bunting's 

 only nesting-place, but in later eras it has availed 

 itself of piles of driftwood on the shores of the Polar 

 seas and rivers, and taken to hiding its pretty nest in 

 them. 



We have now to deal with an equally important 

 assemblage of birds that conceal their nests in holes 

 in timber, or deposit their eggs in such spots without 

 making any other special provision for them. Some 

 of these timber-builders resort to such places as 

 alternative sites, nesting more or less frequently in 

 other concealed or covered situations, as in rocks, 

 in caves, or even in burrows. Others belong to 

 families or genera in which the timber-resorting 

 habit is more or less exceptional. It is also worthy 

 of remark that some of the gaudiest of avine forms 

 resort to such situations ; whilst if the colour of the 

 eggs (or rather want of it) can be taken as any 

 indication, the habit of nesting in timber must be 

 one of great antiquity. As in the other divisions 

 of the present class of concealed or covered nest- 

 builders, we find examples of the habit scattered 

 through many and distantly related families and 

 orders; but although the habit is such a general 



