Fig. (2) Comparison of responses displayed by White-eared Ground-sparrow pairs to different duet stimuli used to simulate territorial intrusions. The responses summarize variation in approach response (PC1) and vocal response (PC2) according to principal components scores (see text for details). Post hoc statistically significant differences are represented by different letters, and lack of letters on top of the whiskers mean that no significant differences were found in the post hoc tests.