Fig. 1

Heat dissipation behaviour representing presence/absence of (a & b) panting, and (c & d) wing-drooping as a function of air temperature (T _air) in two avian species in the Kalahari Desert; Acacia Pied Barbet, Tricholaema leucomelas (32 g), and Marico Flycatcher, Bradornis mariquensis (26 g). Presence of the behaviour = 1, and absence of the behaviour = 0. The logistic regressions represent predicted proportion of heat dissipation. Significant (p < 0.05) relationships are indicated by solid trendlines. Median T _air values where panting (pant ₅₀) or wing-drooping (wing ₅₀) was likely to occur in 50 % of cases are shown in each panel. These species illustrate the variation observed in their heat dissipation responses to T _air (see Additional file 1: Table S2, for statistics); whereas Acacia Pied Barbet showed relatively low pant ₅₀ and wing ₅₀ values, Marico Flycather showed relatively high pant ₅₀ and wing ₅₀ values