Mamma Birds Make Juiced-Up Chicks When Threatened

Many researchers may agree that birds might as well have written the book on parenting. While past research has found that some birds are expert "bad parents," now a new study has determined that birds can be "designer parents" as well, specifically hatching "juiced up" sons when feeling threatened.

That's at least according to a study recently published in the journal Science, which details how after 10 years of observations and tests, a trio of biologist from the University of Arizona have determined that when under threat, mother western bluebirds spike the androgen levels their unborn sons will receive.

Androgen is a broad term for any kind of compound (usually steroid hormones) that encourages characteristically 'male' behavior such as aggression.

In this way, mother bluebirds are ensuring that their sons are born tough in a world that might threaten them more than usual.

But what exactly prompts this? Researchers Renée Duckworth, Virginia Belloni, and Samantha Anderson emphasize in their work that they are not suggesting that mother birds consciously heighten androgen production. Instead, the hormones are likely released as an automatic response to certain kinds of stresses. Those heightened levels then influence the contents of the mother's unlaid eggs.

They add that, as a rule-of-thumb, western bluebirds are naturally more aggressive than many other bird species, bullying one another and mountain bluebirds out of ideal nest cavities. This bullying intensifies when territory is scarce, and it may be that increased levels of aggression help the new generation keep their nests or bully their way into new ones.

A series of experiments even supported this theory, as researchers modified some western bluebird habitats by limiting or expanding the number of nest cavities available. They found that without fail, each generation's androgen levels - and thus, aggressive behavior - adjusted accordingly.

The researchers add that this work can provide some insight into how a species will behave and adapt in stressful conditions, offering important clues for conservationists and behavioral experts alike in the wake of a shrinking natural world.

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