Female European starlings increase their copulation solicitation rate when faced with the risk of polygyny

Since primary females in most polygynous birds receive less male help in feeding nestlings than monogamous females, paired females should try to prevent or delay the settlement of other females. Recently, it has been suggested that a female may copulate repeatedly with her mate to reduce the likelihood that he mates with other females. One of the predictions of this female mate-guarding hypothesis is that females should solicit at times when there is a risk that their male partners will mate with other females. To test this prediction, the response of captive female European starlings, Sturnus vulgaris, that had an exclusive male partner to their male courting a newly introduced female was examined. Resident females significantly increased their copulation solicitation rate after their male started courting the new female. Most of the resident females' copulation solicitations occurred close to the nestbox where their male was trying to attract the newly introduced female, which may suggest that females use the solicitation of copulations to distract their male from the prospecting female. Resident females also behaved aggressively towards the newly introduced females. Male starlings played an active role in moderating female conflicts: they interrupted about 60% of the resident females' aggressive interactions towards the newly introduced females. These results suggest that female starlings use both aggressive behaviour (including song) and the solicitation of copulations to prevent their males from becoming polygynous. (C) 1996 The Association for the Study of Animal Behaviour.