THE CUCKOO. 253 



experiments with all kinds of birds, I find that they will 

 tend with as much care as their own, eggs of widely 

 different species, and presenting size and colour, the 

 latter especially, far different from their own. I have 

 inserted eggs as widely different in colour as it was 

 possible to obtain in nests of most of the commoner 

 species of insessorial birds, and in every case except one, 

 out of some fifty instances, my experiments proved 

 successful, viz., that birds will tend the eggs of kindred 

 species with as much care and attention as their own 

 eggs. I, for my part, do not think the eggs of the 

 Cuckoo vary so greatly as is currently supposed. If a 

 nest is found containing eggs, and one of the number 

 happens to exceed the others in size, or differ from them 

 in colouring matter, it is at once set down to be that of 

 the Cuckoo. It has been ingeniously hinted that para- 

 sitic birds like the Cuckoo became parasites in this wise. 

 A bird in imminent danger of delivery, and without a 

 nest prepared, deposited her egg in an alien nest rather 

 than on the ground, and the convenience of this method 

 may have struck her, arid induced her to repeat the 

 experiment. The birds reared would follow their 

 mothers' peculiar trait, and in course of time the birds 

 thus hatched would outnumber their congeners hatched 

 in the usual way, and thus the habit would become fixed. 

 But my own observations lead me to reject this fanciful 

 theory. If a bird were placed under the circumstances 

 above mentioned, the egg would be deposited upon the 

 ground or in the unfinished nest ; for I have known in- 

 stances of both cases. I consider this peculiar instinct 

 in the Cuckoo has existed as long as the bird itself, and 

 the cause of this to us strange proceeding is as yet one 

 qf the many secrets still in Nature's keeping, while the 



