Chap. VIII.] INSTINCTS OF THE CUCKOO. 333 



lay their eggs in an open nest, manifest a decided pre- 

 ference for nests containing eggs similar in colour to 

 their own. The European species apparently manifests 

 some tendency towards a similar instinct, but not rarely 

 departs from it, as is shown by her laying her dull and 

 pale-coloured eggs in the nest of the Hedge-warbler 

 with bright greenish-blue eggs. Had our cuckoo invari- 

 ably displayed the above instinct, it would assuredly 

 have been added to those which it is assumed must all 

 have been acquired together. The eggs of the Australian 

 Bronze cuckoo vary, according to Mr. Eamsay, to an 

 extraordinary degree in colour ; so that in this respect, 

 as well as in size, natural selection might have secured 

 and fixed any advantageous variation. 



In the case of the European cuckoo, the offspring of 

 the foster-parents are commonly ejected from the nest 

 within three days after the cuckoo is hatched ; and as 

 the latter at this age is in a most helpless condition, Mr. 

 Gould was formerly inclined to believe that the act of 

 ejection was performed by the foster-parents themselves. 

 But he has now received a trustworthy account of a 

 young cuckoo which was actually seen, whilst still blind 

 and not able even to hold up its own head, in the act of 

 ejecting its foster-brothers. One of these was replaced 

 in the nest by the observer, and was again thrown out. 

 With respect to the means by which this strange and 

 odious instinct was acquired, if it were of great import- 

 ance for the young cuckoo, as is probably the case, to 

 receive as much food as possible soon after birth, I can 

 see no special difficulty in its having gradually acquired, 

 during successive generations, the blind desire, the 

 strength, and structure necessary for the work of ejec- 

 tion; for those young cuckoos which had such habits 



