Coloration of the Mouths and Eggs of Birds. 267 



with regard to its occurrence in mammals. In "birds, 

 Mr. G. A. K. Marshall carried out actual experiments with a 

 Mongoose in 1900. This animal (Trans. Ent. Soc. iii. 1903, 

 p. 378) refused " emphatically " an Owl, a Kestrel, a Buff- 

 hacked Egret, a Hobby, and a Drongo, but ate a Turtle- 

 Dove, a Standard-wing Nightjar, a Dwarf Goose (Nettopus), 

 a Moor-hen, and a Wheatear. " Its dislike of the smell of 

 the Drongo was very marked, especially as it was hungry 



at the time ; it made one or two attempts to eat the 



meat, but finally gave it up. In the case of this bird and 

 the Egret, we would therefore seem to have a case of true 

 warning coloration. This is also probably the case with 

 the Wood-Hoopoes {Irrisor and Rhinopomastus), which are 

 very conspicuous both in voice and colour "... and " both 

 of which emit a strong unpleasant smell .... Another 

 bird which has well-known distasteful qualities is the 

 Ground Hornbill {Bucorax cafer)." Prof. Poulton had 

 suggested previously C^ Colours of Animals,' p. 159), that 

 " the gaudy and strongly-contrasted colours of certain 

 tropical species may be of warning significance." 



Conspicousness has always been regarded as of the essence 

 of warning coloration. " Warning colours can be dis- 

 tinguished by the subordination of every other feature to 

 that of conspicuousness. Crude patterns and startlingly 

 contrasted colours are eminently characteristic of a warning 

 appearance" (' Colours of Animals'). Nauseous animals 

 of dull coloration have been regarded as lacking warning 

 coloration. But recent results suggest that, while it may 

 be convenient to thus restrict the term " warning " to those 

 cases of startling conspicuousness which the word so well 

 suggests, the principle comes in wherever unpleasant qualities 

 are present, however dull the colouring. It is the distinctive 

 element in an unacceptable animal's coloration that enables 

 an enemy to difi'erentiate it from an animal 'he is hungry 

 enough for. Distinctiveness may be present even in conceal- 

 ing coloration, where it serves for the animal's identification 

 when the latter element has failed to avert its detection. 

 Conspicuousness is purely an auxiliary quality, though a 



