Western Bluebird (Sialia mexicana) male by Phil Rowntree

Photographer Phil Rowntree captured this image of a male Western Bluebird on the fence along the Virginia Street extension.

The mating habits of Western Bluebirds are a study in wasted testosterone. Males will ferociously defend what they imagine is their territory, grabbing rivals by their legs, bringing them to the ground, standing over them and pecking at them mercilessly. Meanwhile the females copulate with whoever they like. Researchers doing genetic studies have found that almost half the nests contained at least one chick not fathered by the resident male. On the average almost one chick out of five got its DNA from a male other than the imagined master of the roost. So the males might just as well chill out and get along, but tell that to small brains flooded with testosterone.

Links: Wikipedia Cornell Audubon

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