At the time I banded 1571-53435 in 1997, she was one of five nestlings in the first clutch at the Hansen nest box. I had trapped and banded the female parent the previous day. We do not know anything about her history. I had also trapped and checked the band number of the male parent. He was banded as an adult at a nearby nest box on June 7, 1996. 

    I did not recapture the adult bluebirds when the second clutch that included 1531-65295 hatched. It is possible that there was a change in mates between clutches; however, Mrs. Hansen watched the birds on a daily basis and saw nothing to suggest that something had happened to one or both of the original parents. In fact, in 1998, the female parent returned to the Hansen nest box to raise two more broods. However, the male parent did not return. In his place was one of his male offspring from 1996.

    This is the first case of possible incest among bluebirds that we have ever documented. Although it is not understood how bluebirds avoid inter-breeding, it has been suggested that family members may recognize one another. Since these two birds were not clutch mates, they may never have seen one another during their hatch year; hence, the failure to recognize their relationship.