Fig. 3. Allometric plot of peak chemoreceptor discharge rate vs body mass (Table 2). The heavy black regression line was calculated without phylogenetic correction (dotted line indicates 95% confidence interval); the heavy gray regression line was calculated with phylogenetic correction (see text). Regression parameters are summarized in Table 3. Mean values measured in this study are shown in red (lovebird, quail, pigeon, and goose). Mean values from the literature are shown in green (chicken, muscovy duck, emu; see text). The red + green square is the mean value for Anas platyrhynchos (represented by mallard and Pekin ducks) combined from the literature and this study (Table 2). Silhouettes identify specific data points and are not scaled to actual bird size.