CUCKOO PUZZLES 41 



birds which we have seen elsewhere, which is often 

 attributed to their mistaking the cuckoo for a hawk? 

 There remains something puzzling here. 



Wordsworth called the cuckoo a "mystery," 

 and its behavior certainly presents many puzzles. 

 The central one is the mother's evasion of brooding. 

 As is well known, she usually lays her egg on the 

 ground, takes it in her beak (sometimes under her 

 tongue), and flies with it to the previously-selected 

 nest of another bird. Sometimes when the nest 

 is suitable she lays her egg directly in it, but this 

 is often impossible. All is done quickly, cautiously, 

 surreptitiously. There is considerable evidence that 

 each cuckoo keeps as a rule to one kind of nest, 

 and although over a hundred different kinds of 

 foster-parents are on record, the list of favorites 

 is not very long. It includes Hedge-Sparrow, Pied 

 Wagtail, Titlark, Tree Pipit, Robin, Reed Wren, 

 Warblers, Shrikes, and so forth. Unless some big 

 mistake is made the foster-parents incubate the 

 intruded egg, and rear the young cuckoo, who 

 sees to it that they are not distracted by any rival 

 claimants. The parent cuckoos are not known to 

 take any interest in their progeny, and they leave 

 our shores for the South a month or six weeks be- 

 fore the young birds are able to travel. The " para- 

 sitism " works well, and in the Common Cuckoo 

 there is no exception to it. What light can be shed 

 on the puzzle? 



There are three considerations that make the 

 evasion of brooding less perplexing than it appears 



