Letter 14: Inbreeding

Problem I have a strange situation going on:

Our finches had babies about 7 months ago and have since died. But their babies are still alive. They had 2 girls and a boy. We kept the babies together and they have grown up together and are now 6 months old. The females laid eggs in the nest and they have hatched. But as soon as they hatched, the females have been fighting the male away. We took the male out and put it in a seperate cage. The females are raising the babies very well and they dont fight at all. Well here is my question:

When its time for their babies to mate will they be able to find a mate and have normal behaviors. After being raised by two females. Please write me back on what you think I should do and why this would have happened. Thank you.


Comment Hello Jose,

The main problem that you might have is inbreeding: Although the probability of an apparant genetic deficiency is not very high, minor or major deficiencies are more likely to happen in the offspring of sibling marriages than in chicks of normal adults/pairs. So don't let your females have more babies with their brother. Also, read letter no. 11 (Murder?) on my website, please.

The next and minor problem that you mention is one of behavioural "imprinting" or "impregnation": Will the chicks' sexual behaviour be affected by the lack of a father or male model during their adolescence or imprinting period?
I don't think you have to worry about that: If the male parent gets lost (e. g. is killed by a predator), females often manage to raise their young alone, and there are lots of animal species where aunts assist the mothers with no fathers present. So why should there be a major problem?

One thing that a young male without father would miss, however, is the phonetic example of an adult male while producing his display song, which is sung not only during courtship, but at all times of the year. So make sure his father or some other male Zebra Finch is nearby.

The reason for the behaviour you have been observing my be found in the natural development of young Zebra Finches: Females are sexually mature when they are about three months old and have just completed their juvenile molt, so they usualy choose a mate when their brothers still have another two weeks to "go".

In your cage there was no older male partner. So we may assume that the natural search for a sexual partner made the male and at least one of the females mate and produce fertile eggs. But courting and copulating for a few short minutes and rearing young for days and weeks are two different things: The females know that the male is still their brother, and that may also be the reason why they don't compete and fight. For more details, please see my book. Yours,

Hans-Jürgen Martin

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