CHAPTER XIV 
REMOVAL OF EGGS FROM FOSTERERS’ NESTS 
It has been seen that Cuckoo A invariably removed 
one of her dupe’s eggs in exchange for her own 
throughout her record series of twenty-one eggs 
in a season (1920). This was also the case in her 
1921 season, as well as with other Cuckoos of which 
particulars have been given. That this is the usual 
custom of Cuckoos in general is well known, but 
there are many side-issues of this practice which 
are not so familiar. It may be mentioned that 
this instinct of egg-removal by the Cuckoo seems 
occasionally to be in abeyance, and there are 
grounds for believing that at other times it acts 
with increased force, inducing the parasite to 
remove two eggs instead of one. The habit is 
obviously beneficial to Cuckoos, inasmuch as it 
greatly enhances the chances of their eggs being 
accepted by their dupes, and so Cuckoos acquiring 
the habit stand the best chance of survival. But 
it is not safe to take it for granted that the Cuckoo 
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