On the Stomacli-contents of Birds. (535 



XXX. — Bemarks on the Stomach-contents of Birds. 

 By C. F. M. SwYNXERTON, C.M.B O.U. 



On reading the conclusion of ]\Ir. G. L. Bates's extremely 

 interesting account of the Birds of Southern Cameroons 

 (Ibis, 1911, p. 630), I was much struck by the fact that his 

 results, from a not over-minute examination of stomacli- 

 contents of birds, much resembled mine up to December, 

 1908. Out of more than a thousand stomachs of which I 

 liad then noted the insect-contents, I had recognised 

 remains of butterflies in only five. And the instances in 

 which I had actually witnessed an attack of birds on 

 butterflies were hardly more numerous. 



Tbis is evidence that might, not unreasonably, have been 

 held to justify the belief that the birds of Northern Gazaland 

 pi'obably *' do not feed to any great extent on butterflies." 

 Yet when, urged by my friend Mr. G. A. K. Marshall, I 

 lately set to work by special observation and experiment to 

 really get to the bottom of what takes place in this locality, 

 I obtained, within three years, records of several hundred 

 attacks : a total reversal of previous results that seems to 

 suggest that negative evidence drawn from a not over-minute 

 examination of stomach-contents should not be too implicitly 

 relied upon. It may be of interest to go into some of the 

 probable reasons for this. 



1. Removal of wings ; rejection of head ; piecemeal eating. 



It is a fact that, at Chirinda, birds appear usually to 

 swallow their smallest butterflies whole ; that very many 

 [e. g. most of the Picarise that I have observed) do the same 

 for even the largest ; and that some of those that do dis-wing 

 them often do so more or less incompletely ; also that the 

 head of an unpleasant species may, very occasionally, be 

 swallowed and the rest rejected. 



On the other hand, the wings ore very often removed, some 

 birds habitually going to very great trouble in this connexion ; 

 the head has on many occasions, in my observations, been 

 rejected ; and there are many birds that eat their larger 



