VI CAUSES OF THE CUCKOO'S HABITS 261 



habits in the female are doubly remarkable because the 

 males are at least twice as numerous as the females. Brehm 

 supposes that the females wander about principally to find 

 nests in which to lay their eggs. It seems to me that 

 it is rather to be explained by their insatiable sexual 

 desires. 



The female lays her eggs, not like other birds in rapid 

 succession, but at considerable intervals. Most authorities 

 say the interval is from six to eight days. In observed cases 

 a female produced at least two eggs in a week, in others the 

 second was not laid till six days after. There appears, there- 

 fore, to be great variation in this respect. And this agrees 

 with my view of the cause of the peculiarity of the species 

 which is related to the long duration of the egg-producing 

 period. It was probably ultimately determined by the irregular 

 habits of life, the irregular, but on the whole extraordinarily 

 abundant consumption of food, and the varying demands of 

 sexual excitement. Thus our domestic hens have been 

 brought by continued high feeding to lay eggs throughout 

 the greatest part of the year, and to receive the male through- 

 out the whole of this time. The latter condition must tend 

 to increase the number of eggs laid. In man and many 

 domesticated animals even winter has no effect in diminishing 

 generative activity, as it has in most of our wild animals. It 

 is even possible, although not proved, tliat the cuckoo con- 

 tinues to lay eggs during the whole of its period of reproduc- 

 tion — during about two months — and so lays as many as 

 twenty to twenty-four eggs (Brehm). 



That the production of eggs is extended in the cuckoo 

 over so long a period is not therefore the only and ultimate 

 cause of its instinct. But because, in consequence of its mode 

 of feeding and the sexual demands therewith connected, it 

 forms no regular family ties, but is compelled to lead a 

 vagabond life, therefore it does not lay its eggs in rapid sue- 



