Figure 1.

Breeding success in relation to age, starting at age of first breeding. (a) The southern fulmar and (b) the snow petrel. The average observed value for each age is plotted with dotted standard error bars, with predictions from the threshold model. Thresholds are at 6 years and 21 years for the southern fulmar, and at 10 years for the snow petrel. Pearson's correlation coefficients between the prediction of the best model and the averaged observed value are indicated below the curve. ^**p<0.01.