Coloration of the Mouths and Eggs of Birds. 279 



suppose that these Larks and Pipits have abandoned the 

 habit of laying in holes or domed nests so relatively recently 

 that the directive (and misdirective?) markings, no longer of 

 real value, have not had. time to disappear? Why has the 

 Hedge- Sparrow nestling, lying in an open nest, a mouth 

 even more like a Warbler's ? And why has the one Fly- 

 catcher that choses to stray from the normal coloration of 

 its kind also adopted directive markings, indistinguishable 

 from those of the Warblers' ; while at the same time it 

 continues to use a wide-open nest, built in the most open 

 and. brilliantly-lit situation chosen by any Flycatcher that I 

 know, namely (in my experience) on the upper surface of 

 liigh-placed bracken fronds ? And why are the resemblance 

 between the tongues of some of these unrelated birds so 

 nearly exact ? Where a plain yellow mouth like the English 

 Starling's, a twin-spot tongue like the Warblers', and a mouth 

 with black spots at the tips of the tongue and mandibles, are 

 each and all directive, or, at any rate, apparently equally 

 successful in getting abundantly fed, what matter to Accentor 

 and Chloropeta if their mouths should not be quite Warbler- 

 like ? Of what value, on the view of directive markings, is 

 it to the young Chryococcyx to have a mouth coloured like 

 that of the young of its Hyphantornis host ? Were it plain 

 yellow, or crimson, or brown (or even with twin spots or 

 " domino " palate, for the nest is domed), would the Weaver 

 foster-parents, unused to all but plain pink, waste time in 

 uncertainty and the young Cuckoo be ill-nourished ? * 



Some of my questions are, perhaps, not unanswerable, but 

 I have attempted to show that the " directive marking •" 

 principle, though doubtless in some cases present and highly 

 useful, will not explain the whole of the phenomena, nor, 

 indeed, does Mr. Pycraft make any such claim. After all, 

 it is nestling mouth-colour generally that wants explaining — 

 its vividness, its distinctiveness, and its fairly considerable 



* I have since placed a young Weaver {Sitagra ocularia) in the r.est 

 of a Flycatcher {Chloropeta), and watched its feeding^. The Flycatcher 

 seemed to experience no inconvenience whatever from the different 

 mouth-colour and the absence of twin spots, or even from the rapid 

 vibration of the head. 



