LOW HERITABILITY IN MORPHOLOGICAL CHARACTERS OF TENGMALMS OWLS - THE ROLE OF CYCLIC FOOD AND LAYING DATE

In parent-offspring regressions, high heritability estimates of charac ters may simply be due to common environment: the resemblance between the living conditions of parents and their offspring in species showin g restricted natal dispersal. In vole-eating Tengmalm's owls (Aegolius funereus), the natal dispersal and breeding dispersal of adult female s are wide (up to > 1000 km and > 500 km, respectively), whereas adult males are resident. We found that body measurements of 183 recruits b orn in western Finland were independent of parental age and vole abund ance in the birth year. Early-laid eggs produced longer winged recruit s than late-laid eggs. The wing lengths of the daughters showed a sign ificant positive regression on the wing length of their mothers, but t he removal of the maternal effect via laying date lowered this relatio nship. The development time of offspring to the first autumn might als o be crucial for morphological characters of females in their later li fe. Significant regressions were not found between the wing length of the son and his father. The mother-daughter regression was small for l aying date, but positive (p = 0.08) for clutch size. These results sug gest low heritability in breeding and morphological characters of owls and this low heritability may enable plastic adjustment to optimize f itness at any stage in a fluctuating environment. Nonadditive genetic variance also creates variation between offspring characters that are not genetically correlated with the parents and may explain these low heritability estimates.