598 yir. C. F. M. Swyuuerton on 



yarrelli, MotacUla sulphurea, Troglodytes parvulus, Phyllo' 

 scopus trochilus. 



The apparent preference for fowls' eggs against clucks', 

 which the mongoose's nightly choice seems to indicate, may 

 be more apparent than real. It can only be tested by 

 definite experiment. 



Expt. 19. — The following experiment was an uninterrupted 

 continuation of that just described, but, as the eggs used 

 were, purposely, mostly stale ones, it will be best to describe 

 it separately. 



A possible objection to the reality of such preferences as 

 ■were being shown had struck me : even though to human 

 senses every egg offered might l)e equally and perfectly fresh, 

 might not a day or two's difference in their taking be per- 

 ceptible to the mongoose, and be what really decided him to 

 take some and leave others? 1 had some more or less addled 

 eggs on hand, so it seemed well to test the point more fully 

 than I had done with the Sandpiper's e^g. 



The experiment was long, and in many ways highly 

 interesting; but, as stale eggs are "not evidence," I will 

 content myself with summarizing it. 



Amongst arldled eggs. Garden- Warbler, Hedge-Spai'row, 

 Bullfinch, House-Sparrow, Golden Plover, Common Sand- 

 piper, Oyster-catcher, Pheasant, and Red Grouse were eaten 

 more or less readily, even eagerly ; while Great Tit and 

 Eider-Duck (and the new-laid eggs mentioned below) were 

 consistently refused. Amongst practically fresh eggs, House- 

 Sparrow and Bullfinch were thus preferred to Great Tit and 

 Eider. Two highly incubated eggs (Garden-Warbler and 

 Kestrel) were both placed high. Amongst new-laid eggs, 

 Pied Wagtail, Grey Wagtail, Wren, W^illow-Wren, and 

 Domestic Duck were all refused throughout a long experi- 

 ment, and Spotted Flycatcher and Lesser Whitethroat were 

 similarly refused, but were not necessarily placed as low as 

 the others, as the mongoose was now filling up, though he 

 still, after refusing them, ate nearly fresh Sparrow and 

 Bullfinch eggs and addled Hedge-Sparrow and Grouse. 



An apparent preference was shown early for the less 



