Posted by: Sandy Morrissey | July 19, 2016

Proof there can be incest in the bluebird world

A nesting pair in a box at St. Andrews Golf Club are at the same time, husband and wife and brother and sister!

I managed to capture both the male and female and was amazed to discover that both were from the same brood born in another nestbox at St. Andrews last year. Their band numbers were only 2 digits apart.

In the six years that I have banded – over 2000 bluebirds – this is the first time I’ve proven that there can be incest among bluebirds. I’ve always wondered how they could tell a sibling from a non-sibling. Apparently, they can’t.

This couple is on their second brood. The first was successful and the second looks like it will be too. The nestlings show no abnormalities.

My recaptures have shown that bluebirds do not disperse far from their natal nest site. The farthest any has traveled is under 4 miles. So it would make sense that the available mates might be relatives.

Always interesting things to discover along the bluebird trail.

St Andrews female sibling

Female who mated with her brother.


male BB St Andrews

Male who nested with his sister












  1. Very interesting and perhaps you should start a “family tree” on this pair.

    • I’m eventually going to make a “family tree” on all my recaptures. Will be interesting to see if there is more inbreeding.

  2. Tell me it ain’t so!😳

    Very interesting Sandy. Who knew! Two digits apart. Happy they contributed to the BB population, not once but twice this year!

    Best, Neil

    Sent from Neil’s iPad


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