CHAPTER XIII 
FOSTERERS OF THE CUCKOO 
It is quite evident that, difficult as it will be at any 
time to obtain the complete series of eggs laid by 
any one Cuckoo throughout a season, it may be 
regarded as impossible to obtain, or at least to be 
certain that one has obtained, such a series from 
a wandering Cuckoo which might possibly be in- 
dined to deposit her eggs more or less indis- 
criminately in the nests of different species. 
It is, of course, practically impossible to ascertain 
definitely what proportion of Cuckoos incline to 
follow the natural tendency to place all their eggs 
in nests of that species which acted as their own 
fosterers. Personally, I think that Cuckoos, when 
failing to make use of their natural dupes, only do 
so either from necessity or by accident. Such 
cases arise when a selected natural dupe fails to 
provide a nest on the due date — compare Cuckoo A 
when in each of her third and fourth seasons 
she utilised a Tree Pipit’s nest instead (as I 
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