Measurement of heritability of hatching date and chick condition in parasitic jaegers

Abstract

There are few published studies of heritability of reproductive traits in long-lived birds. In parasitic jaegers (Stercorarius parasiticus) breeding on Foula, Shetland, there was no significant heritability in calendar hatching date or relative hatching date, using either mother-offspring, father-offspring, or pooled mother/father - offspring regressions. By contrast, chick body condition (mass corrected for size) was highly heritable. Both traits were important determinants of chick survival from banding until recruitment. High heritability of chick condition was therefore surprising, as characters closely related to fitness are generally assumed to have low heritability. However, chick condition may include a component of structural size, and morphological traits tend to have high heritabilities despite frequently having an important influence on fecundity or viability in birds.