98 THE LIVING ANIMALS OF THE WORLD 
cunning, and the mutual co-operation of both the male and his — at least temporary — wife ; 
hence the disguise. The plan of execution very frequently adopted is for the male to hover 
over the treasure-house of the intended foster-parents hawk-wise. This is sure to call forth an 
attack from the poor little wretches threatened, which ends in an apparently hasty retreat of 
the marauder, followed b}" his fearless assailants. No sooner is the coast clear, however, than 
the wily female, taking her egg in her beak, slips quietly up to the nest and deposits her burden. 
Let us imagine that this home so lately threatened is that of the modest little hedge- 
sparrow, and take a peep during the absence of the owners, after quiet has established itself 
once again. Lying side by side with the tiny sky-blue eggs of the hedge-sparrow we should 
find the relatively large, greyish-green or reddish-grey egg of the cuckoo. What a contrast! 
If the hedge-sparrows notice this too, they evidently do not mind, for they invariably hatch it 
with their own. 
But some birds are not so accommodating as this, and would ruthlessly destroy or reject 
any egg surreptitiously introduced into the nest. Consequently more deception has to be 
practised. The hawk-like garb still serves its purpose to draw off the intended dupes from 
the nest; but this is not enough, for to deposit an egg of the normal cuckoo type would be 
worse than useless, since it would meet with instant destruction on the return of the owners 
of the nest. But the cuckoo, strange to say, has proved equal to the occasion, and meets 
the difficulty by laying an egg to match those in the nest. The Redstart, Wagtail, Sedge- 
warbler, Red-backed Shrike, and Meadow-pipit may be cited as instances of — shall we say 
exclusive? — birds which must be circumvented by “ colourable imitations.” Perhaps the most 
wonderful of the cuckoo successes in this direction is the imitation of the redstart’s egg, 
which is blue. 
Naturally these facts have given rise to much speculation, but even now we cannot regard 
the discussion as finally settled. Some ornithologists held that the egg of every individual 
cuckoo was subject to great variations, and that the place of deposit of each egg was determined 
