124 Campbell, Observations on the Rearing of a Cuckoo. [.J'")",, 



special characters of the other eggs. In my collection one egg, 

 taken with a clutch of Psendogerygone ciilicivoi'a is so finely red- 

 speckled that but for its more rounded smaller end it would be 

 difficult to distinguish from the Fly-eater's ; while another 

 egg, taken with the larger-spotted eggs of EphtJiianura albifrons, 

 is boldly yet sparsely marked with dark spots to suit the case. 

 There are some interesting data to offer in further support of 

 this, indicating the tendencies that have operated to produce 

 these remarkable likenesses. Nothing is on record of a bird 

 leaving its eggs because a Cuckoo's egg was deposited among 

 them, but I have on two occasions discovered the remains of the 

 parasite's e^g on the ground beneath brooding birds. I saw the 

 broken shell of the egg of the Pallid Cuckoo {Cucuhis pallidus) 

 under a nest of the White-shouldered Caterpillar-eater {Lalage 

 tricolor) containing the eggs of the lawful owner, and in another 

 instance found the broken egg of the Narrow-billed Bronze- 

 Cuckoo {C. basalis) beneath the nest of the Red -capped Robin 

 {P . goodenovii). In both these cases the egg that the Cuckoo 

 sought to foist into the care of the other birds with normal 

 habits was so unlike the proper eggs of the nest that it was 

 promptly thrown out. Such difference, of course, will be less 

 noticeable if the nest is a covered one. Occasions are recorded, 

 however, where the eggs of the Cuckoos mentioned were taken 

 in the respective nests referred to, so it is evident that they are 

 not always thrown out. But it is obvious that in a general way 

 those eggs most like the foster-parent's are more likely to be 

 accepted, and the Cuckoos reared therefrom will be still more 

 likely to lay eggs similar to the foster-bird's. Thus in time the 

 suspicious and protective instinct of species of birds has become 

 the selective means by which that species is cruelly saddled with 

 the rearing of a parasite which is so highly developed that it lays 

 an egg surprisingly like its host's. This process of selection has 

 also been the means of altering the size of some Cuckoos' eggs. 

 It is well known that though Cacomaiitis flabellifoniiis and C. 

 variolosus are almost identical in size and plumage the former 

 has much the larger egg. It is large and profusely marked to 

 imitate the general characters of the eggs of the genus Sericorjiis, 

 which acts mainly the part of foster-parent ; but the egg of C. 

 variolosus is sparsely marked with large spots, approximating to 

 those of certain Pctrcecce which are its nest-mates. It is to 

 Darwin's " natural selection " and " survival of the fittest " that 

 we can look for explanation of many changes and habits of bird 

 life. Mr. C. L. Barrett, in his article on " The Origin and 

 Development of Parasitical Habits in the Family CuculidcB','^ 

 sketched the very simple manner in which parasitism might 

 arise, and a search after the same process of events in other 



* The Efint, vi., part 2. 



