THE BUILDERS 



55 



mere vague approximation to the bed of dry leaves which 

 forms the nest ; the likeness is very close, and the protective 

 effect cannot be doubted. Protective mimicry in birds' eggs 

 reaches its highest development when the eggs are laid on 

 the open ground ; and the scanty shoots or branches which 

 usually overhang a pheasant's nest are almost a negligible 

 screen. Pheasants begin to lay about the third week in 

 April, two or three weeks earlier than partridges. The 



'A nestful of 



crow's eggs' 



various strains of wild pheasant now naturalised in England 

 are natives of different Asiatic regions, in which winter and 

 early spring are more severe than in England. This perhaps 

 is one reason for their prompter response to the mild influences 

 of the English seasons, just as the larch introduced from 

 Norway and the Alps comes earlier into leaf than most of our 

 native forest trees. But acclimatised birds after a few years 

 usually acquire habits in conformity with our climate, unless 

 there are definite reasons for maintaining their old ways ; 

 and another and probably a stronger reason for the later lay- 

 ing of the partridge is that it makes its nest among the grass 

 and grain crops rather than in thickets and woods. It there- 

 fore waits until the springing herbage has provided ample 

 cover, as the whitethroat does, which so often shares with 

 it some strip of grass and nettles by the roadside. 



