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THE CUCKOO’S SECRET 
The Law of Survival, and Similarity in Eggs 
The application of the law of survival provides 
a reasonable explanation of one or two other 
phenomena of the Cuckoo problem. Why, for 
instance, do we never find a Cuckoo laying more 
than one egg in a given nest ? This is surely 
answered by a reductio ad absurdum : suppose two 
eggs of the same Cuckoo laid in the same nest — 
what happens when the first of them is hatched ? 
The young Cuckoo’s first instinctive action, as we 
know, is to eject all the other contents of the nest, 
and so overboard goes his brother or sister ! Thus 
a Cuckoo which produced in a season (say) ten 
eggs, laying pairs in five different nests, would at 
best have only five of her progeny reared. 
Why, again, does the Cuckoo lay her egg with 
such astonishing rapidity ? Our discoveries reveal 
for the first time that on the one hand the Cuckoo 
is capable of retaining her egg for hours after she 
has become anxious to lay it, and on the other that, 
as soon as occasion favours her, she can carry out 
the whole process in eight seconds. Obviously, 
the more quickly she lays, the less chance she gives 
of detection, and the less likelihood there is of the 
foster bird forsaking after her visit. In this way 
