INTRASEXUAL COMPETITION AMONG POLYGYNOUSLY MATED FEMALE STARLINGS (STURNUS-VULGARIS)

In southern Sweden, the starling (Sturnus vulgaris) has a variable mat ing system with some males mating monogamously and others attracting s everal females. Mating status affected the reproductive success of fem ales: monogamous and primary females laid larger clutches and fledged more and heavier young than secondary females. This pattern was explai ned by female competition for male help, with the male primarily helpi ng the offspring of highest value (i.e., the oldest brood). However, w hen the nesting attempt of the primary female failed, the success of t he secondary female increased to the same level as that for primary an d monogamous females. The success of the secondary female in terms of fledging success and fledgling size was higher when the secondary fema le hatched her eggs soon after the primary female. This was due to the fact that a male divided his effort between his broods when the age d ifference between broods was small.