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Environmental and genetic variation in the haematocrit of fledgling pied flycatchers Ficedula hypoleuca

Abstract:

We report a field study of the haematocrit of pied flycatcher (Ficedula hypoleuca) nestlings when close to fledging. First a descriptive study was conducted of both fledgling and adult haematocrit over 2 years to analyse correlates of variation in this trait. Then a swapping experiment was performed to see whether variation among fledglings had a measurable genetic component. Average fledgling haematocrits were lower than those of their male and female parents. Intraclass correlations among sibships in fledgling haematocrit were high in both years, indicating that the estimates of resemblance were inflated, probably by common environmental effects. Fledgling haematocrits were unrelated to date and number of young in the nest. Fledglings with a high haematocrit were heavy and had thick breast muscles. There were no significant relationships between the average fledgling haematocrit and those of …