Figure 2.

Proportion of flycatcher choices matching with the portrayed tit tutor choice between two novel symbols (circle or triangle attached at nest-box entrance), as a function of the number of offspring in the heterospecific tutor nest. Lines show logistic regression fits at observed values of offspring number. Solid lines with open squares are for the three Finnish study areas (from top to bottom: OU08, JY07 and JY08); the type of symbol chosen by the tutor had negligible effect and is not included in the fits, but the effects of study area are included to show similarity of slope despite moderately (but non-significantly) differing constants. Dashed lines with black symbols (triangle and circle) are for the one Latvian study area (DA09); the fit includes the effect of the type of symbol (triangle or circle) attached on the tit tutor nest and responses are shown separately for the symbol types, to show significant flycatcher bias towards the triangle. However, the response slopes are very similar for triangles and circles.