Biological Clock Ticks Slower for Female Birds Who Choose Good Mates

In birds as in humans, female fertility declines with age.

But some female birds can slow the ticking of their biological clocks by choosing the right mates, according to results of a study published online last week in the journal Oikos.

Female birds become progressively less fertile as age takes its toll, says biologist Josh Auld of the National Evolutionary Synthesis Center in Durham, North Carolina, and co-author of the Oikos paper.

Older females lay fewer eggs, and they lay them later in the season--at a time when less food is available for their chicks.

But despite abundant evidence of fading fertility in females, scientists knew little about the role played by their mates. "The thought was that males didn't matter," Auld says.

But they do...

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