Polygyny in the blue tit: intra- and inter-sexual conflicts

Abstract

The occurrence and importance of intra- and inter-sexual conflicts were studied in a blue tit,Parus caeruleus, population with a high level of polygyny. Males could increase their chances of becoming polygynous by actively attracting extra females or by displaying towards visiting floater females. Polygynous males allocated their parental care in relation to the hatching interval between the two broods. If the hatching interval was small, males divided their effort between the primary and the secondary nest. If the hatching interval was large, males fed only the nestlings of the primary female. Primary females that had to share male help did not fledge fewer young, but survived less well. Primary females tried to prevent or delay the settlement of secondary females by behaving aggressively towards all intruder females and by guarding their mates. Secondary females fledged more young if they received more help, that is, if the hatching interval was small, but there was no effect on female survival. Secondary females tried to settle early during the breeding season despite severe aggression of primary females. Secondary females needed less time for nest building and incubation and laid a smaller clutch, which increased the probability of hatching their young early relative to the primary brood. It is concluded that sexual conflicts play an important role in shaping the mating system of the blue tit and that parental care is the key factor in these conflicts.