130 Mr. C. F. M. Swynnerton on Rejections [Ibis, 



to remove the heavy interloper, and in the case of a 

 Warbler (Cisticola natalensis) there was suggestive evidence 

 — in the form of a fresh hole made low down in the side 

 of the nest and the position of the ''Cuckoo's" egg in 

 relation to it — of such an attempt previous to the removal 

 of the bird's own eggs. 



4. Rejection of substitutes. — The following was a witnessed 

 example. Finding a nest of Turdus tropicalis, I replaced one 

 of the Thrush's three eggs, blue with bold brown spots and 

 blotches, by a Shrike's {Lanius humeralis) , whitish closely 

 freckled with light brown. Finding that leaves blocked my 

 view, I shortly returned to the nest to remove them, and 

 the bird flew, as I thought, from it. Taking the incident 

 for an acceptance, therefore, I replaced the Shrike's egg 

 with that of a Layard's Bulbul, in which the contrast is even 

 stronger (fig. 16). The bird, on returning, obviously at 

 once noticed it and, leaning over, examined and examined, 

 putting her head down and perhaps turning the egg about ; 

 then slipped away. As she did so, her mate appeared, went 

 through the same actions, and left. The female thereupon 

 at once returned, slipped on to the eggs without further 

 hesitation, and sat. I went down and found the Bulbul's 

 egg gone. 



After this discovery I put in a large white egg, brought 

 me by a Kafir and unidentified. The male (brighter bill) 

 came first this time and definitely, from his movements, 

 must have turned the egg about. He looked and looked at 

 it in the gravest manner (a bird can look grave !), and at last 

 went off. I feared desertion, if the egg should be beyond 

 their powers of removal, so went over quickly and replaced 

 it with a small white egg (Colius striatus minor, fig. 2). 

 One of the birds, almost certainly the female, quickly 

 came back, picked the egg up in her bill, and disappeared 

 with it behind the foliage — perhaps wondering at her maters 

 difficulty ! — then returned and sat on her own two eggs. 

 In a subsequent experiment I watched the Thrushes, again 

 after an inspection by each bird in turn, remove two 

 Shrike's eggs from the nest; but they flew off behind 



