ARE BRIGHT BIRDS DISTASTEFUL - A REANALYSIS OF COTT,H.B. DATA ON THE EDIBILITY OF BIRDS

Detailed studies of edibility of birds suggest a negative correlation between visibility and edibility; in other words, bright birds may be aposematic (Cott 1947, Cott and Benson 1970). Cott used only females to assess visibility (judged not only from plumage but also behaviour and habitat). Here I reanalyse Cott's data, taking into account also plumage conspicuousness of males and females, variation between persons scoring conspicuousness, and statistical problems. For 30 South European passerine birds, irrespective of sex, visibility and plumage conspicuousness were negatively correlated with edibility, but I could not control for phylogenetic association in this smaller sample. For 87 non-passerine birds from southern Africa, irrespective of sex, visibility and plumage conspicuousness were negatively correlated with edibility, both across species and in a matched pairwise comparison of closely related species. For females of 105 passerines from southern Africa, visibility and plumage conspicuousness were negatively correlated with edibility across species; in a pairwise comparison, the trend was significant only for conspicuousness. However, for breeding males of these 105 species, plumage conspicuousness was not correlated with edibility in any analysis. Thus, the male plumage of passerines from southern Africa does not appear to signal distastefulness; it may be sexually selected, or perhaps signal other aspects of prey unprofitability. Further work is needed to establish whether the most important predators in the wild assess avian prey on the scale of edibility used by Cott.