222 MR. C. F. M. SWYNNERTON ON THE 



sometimes when quite replete reject even his greatest favourites with signs of 

 displeasure, or when really hungry accept the most " nauseous '^ insects with 

 every gesture of eagerness : and it is only when the experimenter is aware 

 how hungry or otherwise the bird is that he will know just how much value 

 to attach to these demonstrations. 



Some of these actions have obviously in themselves no relation whatsoever 

 to the animal's likes and dislikes — such as the battering and the mastication 

 referred to above : yet (as I have indicated) they are well worth watching 

 for the manner in which they are performed. In this category comes the 

 wiping of the bill. It is a very usual action after food has been eaten, 

 particularly if it has required much preparation and left juice or fluff on the 

 bill. It may even be continued at intervals, as I have seen, for some time 

 afterwards, and, I fully agree, does not necessarily indicate the very smallest 

 dislike of the object swallowed. Yet there is a wiping of the bill — and it is 

 not, I think, always very difficult to recognize for the experimenter who has 

 come to know it — that does seem to indicate dislike (when an insect has been 

 tried), and there is also a wiping of the bill that may accompany refusal 

 without trial. With my kingfisher and at least two of my bulbuls this form 

 of refusal (without tasting) of a proffered insect was by no means unusual, 

 and it occurred in other birds too; and I have on a few occasions, by merely 

 holding up a very low-grade insect in view of all the cages at a time when 

 the various occupants were by no means hungry enough for it, produced the 

 simultaneous vigorous wiping of several bills. I have seen my kingfisher 

 thus wipe his bill repeatedly when an Amauris albimaculata or lohengula 

 merely entered the verandah and remained flying about in it for two or three 

 minutes : it was one of the methods adopted by my older wood-hoopoe 

 (Irrisor erythrorliynchus) apparently to dissuade a younger bird from eating a 

 Danaida ; and much bill-rubbing is sometimes indulged in before and in the 

 intervals of attempts to bring up an insect, the eating of which has resulted 

 in nausea. This last instance indeed would seem to suggest that there may 

 be a simple physiological explanation at the back of all these cases of bill- 

 wiping, namely, the abundant reflex secretion of saliva that at any rate in 

 man and certain other mammals is known to accompany actual nausea 

 or the sight of objects that experience or training has suggested to be of a 

 nauseating character. From cases like that of the wood-hoopoe one might 

 even suspect, were one inclined to theorize, that as spitting in man has 

 gone on from (quite possibly) this beginning to become a conventional 

 sign of contempt, so bill-wiping may have become stereotyped in some 

 bird-languages as, inter alia, a signal of un acceptability or warning. 



That there are cases in which it is by no means easy to decide between two 

 or more possible motives it would be foolish to deny. Thus I at first tended 

 largely to put down to grave suspicion actions that I have since learnt to 

 attribute in most cases to mere disinclination — or mere initial caution. Even 



