Origin of Species Variorum

laid by her, so as to have deceived certain foster-parents, or, as is more probable, to have been hatched within some shorter period (for it is asserted that there is a relation between the size of eggs and the period of incubation), then there is no difficulty in believing that a race or species might have been formed which would have laid smaller and smaller eggs; for these would have been more safely hatched and reared. Mr. Ramsay remarks that two of the Australian cuckoos, when they lay their eggs in an open or not domed nest, manifest a decided preference for nests containing eggs similar to their own. The European species certainly 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 its bright greenish-blue eggs: had she invariably 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. Ramsay, in an extraordinary manner in colour; so that in this respect, as well as in size, natural selection assuredly might have secured and fixed any advantageous variation. ↑

With respect to the last point insisted on— namely, of the young European cuckoo ejecting its fosterbrothers— must first be remarked that Mr. Gould, who has paid particular attention to this subject, is convinced that the belief is an error; he asserts that the young foster-birds are generally ejected during the first three days, when the young cuckoo is quite power less; he maintains that the young cuckoo exerts, by its hunger-cries, or by some other means, such a fascination over its foster-parents, that it alone receives food, so that the others are starved to death, and are then thrown out, like the egg-shells or the excrement, by the old