Figure 1.

Clutch size and offspring sex ratio for females mated to males with single cavities and surplus cavities in their territories during the pairing and egg-laying stages (clutch size: single; n=32, surplus; n=32, p<0.04; offspring sex ratio as proportion of sons: single; n=20, surplus; n=17, p<0.04). Offspring sex ratios were determined for a subset of the nests used in the analysis of clutch size. The mean proportion of sons for each treatment was derived from model parameters fitted during statistical analysis of this smaller dataset. Proportions of sons (open symbols), daughters (stippled symbols) and unsexed offspring (striped symbols) are represented.