White flickers

 

This beautiful and striking bird is a partial albino Northern Flicker, photographed in Massachusetts in Sep 2015 by Michael Beagan.

A second, very similar, bird had been photographed nearby in 2012 by John Harrison, and – besides being very attractive birds – the two provide a good opportunity to discuss some of the details of coloration and abnormal plumage. They are remarkably similar, and there is a fairly simple explanation for their coloration: a reduction in melanin, the same as any other partial albino.

 

And for comparison – a normal Northern Flicker:

 

First, to review the basics of color in bird feathers: Almost all colors in bird feathers are produced by two classes of pigments: melanins for black, gray, and brown, and carotenoids for bright yellow to red. Many birds, such as Northern Flicker, combine these two classes of pigments to produce unique and complex patterns of black, brown, yellow, red, etc, but essentially all birds use the same few pigments. Furthermore, there are two types of melanin (a black-gray pigment and a reddish-brown pigment) and either can be affected independently by albinism.

see my post about albinism and melanin in birds

Simplicity is the rule

 

Suppose you wanted to paint a pattern of black and yellow stripes on a sheet of white paper. If you started at one side and painted yellow stripes and then black stripes in turn across the sheet, that’s complicated and you would risk leaving some thin white gaps showing where the stripes didn’t quite meet. To avoid that you could paint the yellow stripes a little wider than they needed to be, so that the black stripes would cover all of the remaining white (and some of the yellow). But why bother with all that extra work with the yellow stripes? Just paint the entire sheet yellow, then paint black stripes over that.

That’s not a perfect analogy, because a bird can only deposit color once as each feather grows, more like a printer coloring a sheet of paper as it passes through the ink jets. But the point remains – it is far simpler to just turn on the yellow pigment and leave it on to color the entire feather yellow, with intermittent bursts of black to form a barred pattern as the feather grows.

So what’s going on here?

It is clear that both of these flickers are missing most of the melanin from their feathers. To be more precise, it is likely that they are missing the gray-black pigment eumelanin, which creates the black bars and spots along with much of the dark dusky color of the back. The absence of eumelanin reveals the rust- or buff-colored phaeomelanin, mainly in the pinkish-brown color on the head.

The lack of melanin also reveals the yellow (carotenoid) pigments that exist throughout the wings and tail.

The “mustache” mark on these birds deserves some discussion. This marking is present only on males, and on male Yellow-shafted Northern Flickers (of Canada and the eastern US) it is black. Since these two albino birds are lacking the melanin needed to produce a black stripe, we might conclude that the absence of a mark there (as on the 2012 bird) is expected and we cannot determine the sex of that bird. But the 2015 bird shows a bold red stripe there, like a Red-shafted Northern Flicker from the western US. It’s clearly not a vagrant from the west, as it shows yellow wings and tail, and a red crescent on the nape, all characteristic of the expected Yellow-shafted subspecies. The explanation is that all male Yellow-shafted Flickers have both red and black pigments in the mustache mark. Normally the black color masks the red, but in this case the black pigment is missing while the red is undiminished, producing a bright red mustache. It follows then that the 2012 bird, lacking any trace of a mustache, must be a female.