Repeatability of parental effort in male and female Pied Flycatchers as measured with doubly labeled water

Intensity df parental care is one of the critical factors affecting offspri ng growth and final size and thus is a key variable in life-history evoluti on. In the study population of Pied Flycatchers (Ficedula hypoleuca), it:wa s previously shown that maternal daily energy expenditure was an important source of variance in offspring size and likelihood of infection by blood p arasites. Thus, energy expenditure may be considered a parental-performance effect, and variation among females in the intensity of parental care they provide might itself be influenced by genetic differences, affording the o pportunity for evolutionary change. To address whether parental work load i s a consistent trait and thus may retain additive genetic variance, the sam e individuals were scored for mass-independent daily energy expenditure (DE E): across two consecutive breeding seasons, while feeding nestlings close to fledging: While DEE of females was significantly repeatable between year s, this was not the case for males. DEE may retain additive genetic varianc e in females; although its expression may be obscured in males by their les s constrained activity budgets and lower confidence of paternity..