Wild birds detect quinine on artificial Batesian models

Abstract

EVIDENCE I acquired during an experiment on the evolution of Batesian mimicry indicated that under some circumstances birds can detect quinine dihydrochloride on flour–lard pastry baits. The results of some previous mimicry experiments^1–5, in which pastry baits were presented to wild birds, may need to be re-evaluated because of their tacit assumption that birds can only detect by taste the quinine used to make the models unpalatable. Quinine salts used were the hydrochloride^2,3 or dihydrochloride^1,5. Pilecki and O'Donald's “solution of quinine”4 was presumably quinine hydrochloride, which they used previously. Quinine monohydrochloride has only 1:16 solubility⁶, so Morrell and Turner² probably used the more soluble dihydrochloride to make their 75% solution. Birds in an experiment of Ikin and Turner¹ took nearly as many perfect mimics of two different models as palatable controls, though very few models (70% quinine) were taken. These authors suggested that birds in previous experiments^2,5 may have distinguished “models from ‘perfect’ mimics, possibly because the quinine causes a slight yellowing of the pastry”. So far as I can determine, however, a specific control for detection of quinine has never been conducted.