286 Mr. C. F. M.. Swynnerton on the 



and lemur. It may be that the nestling is intermediate. 

 But even a very slightly unpleasant species will, if it be 

 unpleasant at all, derive much advantage from a con- 

 spicuous and easily remembered appearance. The only 

 question is, Can it safely carry it — as a highly nauseous 

 species often can ? The shut mouth of a young bird is a 

 sufficient shield from this point of view. Being seen, never- 

 theless, its one remaining chance of averting attack is 

 identification. Hence the distinctive colouring. 



It was interesting that both the Doves examined had very 

 dull mouths. Their mode of feeding, and the fact that they 

 do not open their mouths when approached — they cannot to 

 any great extent — had led me to expect this. Young Night- 

 jars, again (in my experience), tend only to open their 

 mouths when they are actually touched — doubtless a part 

 of the procryptic scheme — and their very large canvases 

 remain quite unpainted. 



Other distinctive characteristics. — I have referred to the 

 extraordinary tongue-action and wheezing sound of young 

 Centropus burchelli, also to the nestling notes of Pycnonotiis 

 layardi and the extraordinary vibration of the head that 

 the same nestling possesses in common with Hyphantornis 

 jamesoni. It is a regular Ploceid character, and it would be 

 interesting to know whether it is the exception or the rule in 

 Pycnonotus. There is almost as much distinctiveness and 

 diversity in the food-calls and the birds'* actions as there is 

 in the mouth-patterns. The soft long-drawn '^pwee pwee"" 

 of young Chalco])elia afra (least relished of all our Doves), 

 compared by my wife to the very distant call of a Gull ; the 

 loud musical trill, like a cricket or tree-frog, of young 

 Macronyx croceus ; the wheeze of Centropus; the rather bell - 

 like squeak of a Culiuspasser ; and the rather short pleasing 

 note, hard to describe but differing from all the above, of 

 Cisticola natalensis, are examples. The marked differences 

 between them can, at first sight, serve no very useful pur- 

 pose in relation to the parent bird, though the mere fact that 

 the species, and the adult call-notes, are different might 



