1 91 8.] bij Birds of Eygs unlike their own. 131 



the foliage with them, and I again failed to see their fiaal 

 fate. A small boy, who had seen the commencement of 

 the first experiment from a different angle, told me later 

 that the supposed acceptance of the original Shrike's egg 

 was not one, the bird being still a couple of feet from 

 the nest when my approach frightened her away. 



In my experiments generally I actually witnessed only 

 a few of the rejections : most of the experiments I had 

 not time to watch, and in those I did watch initial 

 acceptance was the more general rule. In very few cases, 

 again, did I recover the " Cuckooes " egg. It was evidently 

 usually carried away, as excreta and egg-shells so com- 

 monly are, probably to avoid revealing the nest to enemies. 

 In some cases — for all I know, in most — the bird definitely 

 pierced the shell ; so that even if the Cuckoo had witnessed 

 the ejection, there would be no possibility of her using the 

 egg again. 



5. Closer selection. — I placed a specially richly-coloured 

 egg of Pycnonotus layardi in the nest of a Yellow-streaked 

 Bulbul [Phyllastrephus flavistriatus) , removing one of the 

 latter's. Unluckily, the small boy who had showed me 

 the nest at once announced another within a few yards, 

 and I went to inspect. Returning within a very few 

 minutes, I found the Yellow-streaked Bulbuls just drawing 

 off and the Layard BulbuFs egg still in the nest, but 

 spiked. The eggs were by no means unlike, excepting for 

 the fact that in the latter the darker markings were less 

 definitely gathered into a zone. I have already mentioned 

 'the rejection of an egg of Sitayra ocularia by Hyphantornis 

 niyriceps laying spotted blue eggs (* Ibis,' Oct. 1916, 

 pp. 558-9). Though not really like each other, these 

 eggs were not greatly in contrast in a dark nest. But a 

 far better case than either of these was that of a Layard's 

 Bulbul that rejected eggs of its own species that differed 

 very slightly indeed from its own, and even its own egg 

 when its zone was widened by the addition of markings 

 (of the colour and size of the others) in water-colour 

 paint. I will give the whole experiment below. The last 



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