Figure 1.

An idealized representation of the relationship between clutch size and lay date under absolute and relative modes of clutch-size determination (after von Haartman, ref. 15). In the absolute mode, clutch size responds to lay date such that a change to an earlier lay date (e.g., in response to warming) would result in larger clutches being laid, with the population shifting up the same regression line (dashed portion). Under the relative mode, earlier lay dates would result in a shifting to the left of the clutch-size/lay-date regression without any shift in mean clutch size. Note that these simplified graphs assume constancy of the regression slope with changes in lay date.