150 Mr. C. F. M. Swynnerton on Rejecliuns [Ibis, 



between Lis two Cuckoos and the prehensile feet were freely 

 used to prevent ejection_, but the stronger Cuckoo eventually 

 threw the weaker from the nest, and repeated tlie perform- 

 ance on its being replaced. Experiments of my own, as well 

 as general observation with regard to Cuckoo nestlings, tell 

 a^iainst the view that the hosts ever eject or neglect the 

 latter through noticing the differences between them and. 

 their own young, and the probability generally is, I am 

 inclined to think, rather a'^ainst the explanation of the 

 coloration of the young Koel that I shall refer to below. 



The Cuckoo's defence against the attempts to prevent 

 lier placing the egg in the nest must, where she does not 

 intimidate, lie largely in cunning and adroitness and in ob- 

 servations of the birds for the purpose of choosing a suitable 

 moment. I am thinking especially of the case of a colony 

 and of those Cuckoos which lay in the nests of Corvidse, 

 for the problem would be simpler, though not always quite 

 simple, in the case of isolated nests of small birds the eggs 

 of which were not yet being incubated. The thickness and 

 strength of the shell, again, must occasionally save it from 

 breakage when it comes to a scuffle, as well as permitting it 

 to be carried about with impunity. It is even possible that 

 the extraordinarily tough skin of the Honey-guide, selected 

 primarily in another connection, may be highly serviceable 

 to it as a parasite in enabling it to face attacks from heavy 

 Barbets and its other strong victims, Haagner and Iv}'^ 

 (Journ. S. A. O. U. iii. 1907, p. 103) speak of ''all the 

 Honey-guides" as ''very persistent in 'commandeering' the 

 nest-hole of other birds, as they are generally fiercely attacked 

 by the foster-parents," and the accounts one has read of the 

 actual encounters certainly suggest that they show much 

 fearlessness of their heavier antaiionists. Wliether the 

 hawk-like appearance of several Cuckoos is backed up by 

 a, hawk-like approach to the nest and the insertion of the 

 egg facilitated by the consequent intimidation of the owners 

 is still, I take it, a ])oiiit for observation. It has been sug- 

 gested, I believe, that the Drongo-Cuckoos are enabled by 

 their likeness to their hosts to approach the latter's nests 



