Date: 6/25/18 11:44 pm
From: Barbara Millikan <barbara.millikan...>
Subject: [obol] out of area odd colored hairy woodpecker

Despite our not filling out feeders for the summer, this guy has been
hanging around, ever hopeful. He looked like some hybrid of a hairy
woodpecker and a flicker, but I knew that couldn’t be, so I contacted
Cornell’s Lab of Ornithology, sent them this pic, and got this reply:

“Now that I see your photo, I recognize what this is: a "Dirty Hairy!" It's
normal Hairy Woodpecker (no interbreeding required) who just happens to
have yellow feathers, most likely from environmental staining.

There are two different effects that can cause Downy or Hairy Woodpeckers
to have yellow feathers: staining and carotenism. Staining is an external
environmental effect, which happens when tannins from soot or tree sap
coatthe feathers and stain them a dull yellow or brown. This typically
affects a broad swath of body feathers, along with the underside of the
tail, and results in a relatively dull, dirty yellow color. Birders
sometimes nickname these birds "Dirty Downy" or "Dirty Hairy."

Carotenism is a rare genetic mutation that affects the placement or type of
carotenoid pigments, which are responsible for yellow, orange, and red
colors. In many cases, it changes the color of a normally colored area,
resulting in things like a yellow Cardinal, or a male Downy with a yellow
head patch instead of red. However, there is another type of carotenism
known to happen in Hairy Woodpeckers on rare occasion, where normally white
outer tail feathers become yellow. This is typically just a few specific
feathers, and a fairly clean, bright yellow color.

Aside from the yellow color, the bird in your photo looks to me like a
normal male Hairy Woodpecker: the body shape, beak shape and proportional
size, and color pattern (if you can imagine the yellow areas as white) are
all correct. The relatively large beak, along with the lack of black spots
on the outer tail feathers, distinguish it as a Hairy rather than a Downy;
and the red patch on the back of the head marks it as a male. And, based on
the brownish hue of the yellow (it reminds me of a tobacco smoker's yellow
teeth) and the way it is spread across the head, wings, and body in addition
to the tail, with varying degrees of intensity, I suspect that in this case
the yellow is caused by staining."

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