Electronic Supplementary Material 2
Figure 1. An example showing how the duration of effective breeding (DEB) was estimated from data on age-specific breeding success. The
data shown are simulated. We defined the duration of effective breeding as the length of time during which the average individual of one sex can
expect a substantial amount of reproductive success. To estimate this, a quadratic function was fitted to data on mean number of offspring
produced at different ages. The duration of effective breeding for individuals of one sex was then calculated as the time period in their lifespan
(length of the x-axis) during which the quadratic curve was at least one-fourth the maximum. If the predicted age at one-fourth of the maximum
was more extreme than either the minimum and/or the maximum age reported breeding, then the minimum and/or maximum breeding ages were
used.
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