Fig. 3.

Tinkerbird songs diverge in sympatry in peak frequency and rate after controlling for percent tree cover, elevation, longitude, and site. Peak song frequencies (A) diverge in sympatry in both P. bilineatus and P. subsulphureus, whereas song rate (B) shifts in P. subsulphureus but not in P. bilineatus. Dashed lines show the range of mean peak song frequencies of individuals before controlling for environmental and geographic factors, illustrating that some song frequencies of each species are similar in allopatry. Error bars are SEM; *, P < 0.05; **, P < 0.01; NS, not significant.