PATERNAL CARE IN PIED FLYCATCHERS FICEDULA-HYPOLEUCA - ENERGY-EXPENDITURE IN RELATION TO PLUMAGE COLOR AND MATING STATUS

Females may benefit from expending more resources in care of offspring sired by sexually attractive males than by those of unattractive male s in species with biparental care. Attractive males may therefore redu ce their share of parental expenditure to increase own survivorship an d to further mating success. On the other hand, if direct benefits thr ough male care are important for female mate choice, sexually attracti ve males may be expected to have a higher parental expenditure than un attractive males. We measured daily energy expenditure of attractive a nd unattractive (i.e. brightly and dull coloured) male Pied Flycatcher s Ficedula hypoleuca during a period of intensive parental care applyi ng the doubly-labelled water technique. We did not find any consistent differences in energy expenditure between bright and dull males, lend ing little direct support to either hypotheses. Combined with previous studies of the same species, we suggest that bright males are more ef ficient in bringing food to the brood per unit of energy spent. Polyga mously mated males divide their feeding effort among the primary and s econdary brood(s), although most care is given to the primary brood. W e found that bigamous males had higher daily energy expenditures than monogamous males. This result suggests that polygamy is associated wit h energetic costs to males, possibly related to the need of travel bet ween nests but perhaps also to an overall higher parental investment. We argue that costs to males should be incorporated in discussions on the evolution of polygamy.