126 JOTTINGS ABOUT BIRDS. 



it to rear its own young; but there can be little 

 doubt that this early passage to its winter quarters 

 is a result and not a cause of parasitic instincts. 

 The Cuckoo having no family ties is at, liberty to 

 migrate as early as it may choose ; not only so, but 

 there are numbers of parasitic species that either do 

 not migrate at all, or whose periodical movements 

 are but trifling in comparison with those of the 

 European species. Secondly, it is affirmed and I 

 think the theory was first mooted by Dr. E. 

 Baldamus, who has perhaps studied the intricate 

 Cuckoo question more assiduously than any other 

 naturalist, that the Cuckoo is a parasite because 

 its eggs are produced only at long intervals, so that 

 one general incubation would be impossible. Here, 

 again, it seems far more probable that the inter- 

 mittent development of the eggs is a result rather 

 than a cause of parasitism ; whilst it has been 

 suggested that this slow rate of laying is an 

 acquired habit (possibly through natural selection), 

 enabling the mother bird to have sufficient time to 

 find a suitable nest in the interval between each 

 egg. Thirdly, some writers have suggested that 

 the alleged gluttony of the male Cuckoo is the 

 reason for the slow development of the eggs, his 

 sexual instincts being subordinated to his abnormal 



