The Loh Down On Science

Stressed Moms

The benefits of stress, in pregnant birds.

Feeling STRESSED? Good!

This is Sandra Tsing Loh with the Loh Down on Science

and with the benefits of angst. At least when you're a pregnant bird.

When expecting mother birds are stressed--by, say, a scarcity of food after flying all day--a hormone, corticosterone, accumulates in their egg yolk.

More stress, more steroid.

To discover corticosterone's effects, Canadian biologists injected it into about thirty freshly-laid European starling eggs.

Three weeks after the chicks hatched, the researchers. . . BORROWED them, gave them all a physical, and tested their flying ability. Thirty chicks not treated with corticosterone were also tested.

Chicks dosed with the hormone had larger breasts--that is, flight muscles--as well as bigger wings AND more enzymes that fuel flight.

This translated into more powerful and efficient flying. Handy when winging around for slim pickin's.

The results, in an, um, EGG shell? Ma's stress signal warns her future young about the less-than-ideal conditions they'll be born into. In response, they pump up their pectorals to cope.

Interestingly enough, when HUMAN pregnant moms are stressed they only anxiously pre-purchase more Baby Einstein videos but. . . Topic for another day.


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