MATE DESERTION BY PRIMARY FEMALE EUROPEAN STARLINGS AT THE END OF THENESTING STAGE

In a 8-year study of the facultatively polygynous European Starling St urnus vulgaris, apparent female mate desertion during the incubation/n estling period occurred in nine (7%) out of 132 breeding attempts. Des ertion rates by primary (17%) and secondary (13%) females of polygynou s mates were significantly higher than those by monogamous females (0% ). True female mate desertion (in the sense that the male assumed pare ntal care) occurred in three primary broods only. In all three cases, the primary females had received no male help during the first part of the nestling stage because their mate was attracting or courting an a dditional female at that time, and they deserted when the nestlings we re about 16 days old (about five days before fledging). This is the fi rst report of mate desertion at the end of the nestling cycle by prima ry females in any polygynous bird species. Mate desertion may be a str ategy used by some primary females to force their mate to increase his overall investment in their brood. Female mate desertion in the Starl ing seems to be linked to the occurrence of polygyny and may be typica l for populations where males trade mate attraction against feeding ne stlings.