title: 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 the adults caring for them. Nest mite ectoparasites negatively affected fledgling haematocrit. The haematocrits of adults did not differ between sexes or years and in both sexes were unrelated to breeding date, body mass, age, clutch size or number of young reared. Females, but not males, caring for fledglings in nests infested by mites had a lower haematocrit than those rearing young in mite-free nests. The cross-fostering experiment indicated that almost all measured variation in haematocrit was explained by the nest where the bird was reared (67.2% of the explained variance), not by their nest of origin (7.8%), meaning that there was a very small, non-significant resemblance in the haematocrit of genetically related sibs when reared in different environments while unrelated nestlings reared in the same nestbox had similar haematocrits. The low proportion of variance explained by the familial component may be due to the high connection of haematocrit to fitness.
authors.affiliation: Departamento de Biología Animal, Universidad de Alcalá, E-28871 Alcalá de Henares, Madrid, Spain e-mail: bnjps@bioani.alcala.es, Fax: +34-91-8855080 , , , , , , ES.
authors.forename: Jaime
authors.initials: J
authors.lastname: Potti
authors.affiliation: Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales-CSIC, c/José Gutiérrez Abascal 2, E-28006 Madrid, Spain, , , , , , ES.
authors.forename: Juan
authors.initials: J
authors.lastname: Moreno
authors.affiliation: Departamento de Biología Animal, Universidad de Alcalá, E-28871 Alcalá de Henares, Madrid, Spain e-mail: bnjps@bioani.alcala.es, Fax: +34-91-8855080 , , , , , , ES.
authors.forename: Santiago
authors.initials: S
authors.lastname: Merino
authors.affiliation: Departamento de Biología Animal, Universidad de Alcalá, E-28871 Alcalá de Henares, Madrid, Spain e-mail: bnjps@bioani.alcala.es, Fax: +34-91-8855080 , , , , , , ES.
authors.forename: Oscar
authors.initials: O
authors.lastname: Frías
authors.affiliation: Departamento de Biología Animal, Universidad de Alcalá, E-28871 Alcalá de Henares, Madrid, Spain e-mail: bnjps@bioani.alcala.es, Fax: +34-91-8855080 , , , , , , ES.
authors.forename: Rosa
authors.initials: R
authors.lastname: Rodríguez
keywords: Blood; Cross-fostering experiment; Heritability; Key words Birds; Repeatability