Sunday, May 09, 2010

Science Sunday: An Ode To Bluebirds

The bluebird carries the sky on its back.
I love birds and would be hard pressed to name a favorite species, but I have a special place in my heart for bluebirds.
My fondness goes beyond the bluebird's precocity, song making and lovely markings (the male and female are stunningly different). While never faced with outright extinction, the population in rural Chester County, Pennsylvania where I lived for many years had become depleted as they lost habitat and had to compete with two introduced species -- starlings and house sparrows -- that took over many of their nesting sites, killing their young and smashing their eggs.

But bluebirds have come back strong in Chester County because of nesting box programs. Same at the mountain retreat.
The bluebird (Sialia sialis in its Eastern incarnation) is a medium-sized, mostly insectivorous or omnivorous member of the thrush family. The males typical have blue and red plumage while the females are less brightly colored. Their song is a soft warble, heard often during breeding season and they seldom sing without quivering their wings.

Bluebirds are extremely territorial and prefer open grassland with scattered trees, which is exactly the kind of habitat off the back deck of the mountain retreat. Absent nesting boxes, they nest in cavities like woodpeckers, typically producing between two and four broods during the spring and summer.

Males take the lead in the breeding ritual, identifying potential nest sites and attracting prospective mates to those sites with by singing and quivering their wings and then placing nesting material in a box or cavity. If the female accepts the male and the nesting site, she alone builds the nest and incubates the eggs.

As Paul McCartney sang to Linda:

Late at night when the wind is still, I'll come flying through your door. And you'll know what love is for, I'm a bluebird.
IMAGES: John James Audubon paintings of bluebirds

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