Look at Every Bird


Brewer’s Blackbird, in the jargon of birders, are “dirt birds,” too common to be interesting. There were certainly hundreds of the along Cemetery Road in New Meadows, when WC was out with his camera Sunday morning. Under the overcast skies, the purple and green sheens of the males was especially vivid. So when one held a fencepost perch as WC drove by, WC took a few shots.

Brewer's Blackbird male, New Meadows, Idaho

Brewer’s Blackbird male, New Meadows, Idaho

As the name says, this is a black bird, with only the male’s pale eye for contrast. The photo was good but not great, so WC watched for another shot. A rousing male – “rousing” is when a bird fluffs out its feathers – showed a flash of white. There shouldn’t be white, because, you know, “black bird.”

Even though the bird had its back to the camera, WC tried for another shot of the bird rousing. And it did. It’s not a great photo, but you can see white in two places.

Brewer's Blackbird rousing, flashing white

Brewer’s Blackbird rousing, flashing white

There’s a pure white feather in the primaries on the right wing, and more white in the thigh. After that second rouse, he gave me a look over the shoulder, with the white primary – the second primary, P2 – plainly visible.

Brewer's Blackbird displaying leucistic primary feather

Brewer’s Blackbird displaying leucistic primary feather

Partial or selective loss of a color is called “leucism,” and birds that display it are said to be “leucistic.” The white is an absence of melanin, the dark pigment that makes the blackbird black.

Note that the white primary is much more worn than the feathers around it. Melanin toughens feathers; the effect is well documented but the chemical reasons aren’t all puzzled out yet. Nice to see clear evidence of the effect.

So the moral of this short blog post is to always look at the bird, all the birds. You never know what you’ll see.

Advertisements

One thought on “Look at Every Bird

  1. Thanks for this explanation of leucism. It answers a question that arose about a week ago when I noticed white coloration in a robin in flight and when rousing but not as it walked about pecking for food.

    paul eaglin

Comments are closed.