Pale Chickadee at Sycamore Landing - not leucistic?

[Scott Young]

Recently, a pale chickadee (Carolina?) has been observed at the C&O Canal--Sycamore Landing hotspot by numerous birders, initially by Nathan Tea. Most have described it as leucistic, but in my preparation for a brief presentation to our club on bird coloration, I came to the conclusion that it is not leucistic. Instead, it most likely has the "Brown" mutation. This mutation reduces the amount of the black eumelanin in melanocytes without affecting the brown pheomelanin. The number of pigment granules and the number of melanocytes containing them are normal.

It is clear that it is not leucistic as that phenomenon leads to lack of melanocytes and loss of all brown and black in those areas, either spottily or more generally. This chickadee has a universally brown cap and bib and not the appearance of all white or occasional white feathers within the cap and bib.

Another consideration is the "Ino" mutation but that affects the pheomelanin as well as the eumelanin leading to a very faint brown.

I received the suggestion that I mention this here to see if there were other thoughts and if there is agreement, then it would be appropriate to change the eBird descriptions to "Brown mutation."

An example picture of the bird is here: https://macaulaylibrary.org/asset/308069661

A good reference to color disorders by Hein van Grouw is here:

https://static1.squarespace.com/static/52afb651e4b0c8fba4ecb28a/t/5c633ea3104c7b07ad5254a9/1550007979018/Grouw+Color+Aberrations.pdf

Thank you.

Scott Young

Gaithersburg

[Gene Scarpulla]

Scott,

The Carolina Chickadee definitely does not have the color aberration 'Leucism' which would be characterized by all white plumage and skin ('100% leucism') or white feathers in only some regions ('Partial Leucism').  The Carolina Chickadee appears to have the color aberration 'Brown' where normal black becomes brown; normal brown becomes light brown; and normal reddish-/yellowish-brown remains normal.

I have two short articles on this subject that will be published in the spring 2021 issue of Maryland Birdlife. One involves a House Sparrow and the other involves a Turkey Vulture, both with the color aberration 'Brown'.  You might want to consider elaborating a bit more and publishing your note in Maryland Birdlife, as well.  Feel free to contact me for further information.

Gene

Eugene J. Scarpulla

Editor, The Maryland Entomologist

Editor, Maryland Birdlife

Bowie, Maryland

ejscarp (at) comcast (dot) net

[Gabriel Foley]

Thanks for bringing this up, Scott! I'll update my description from "leucistic" to "brown mutation".

Gabriel

North Bethesda

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Gabriel J. Foley, M.Sc.

Atlas Coordinator

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Maryland & DC Breeding Bird Atlas 3

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[Walter Ellison]

Hi All,

I find this of interest because the Balck-capped Chickadee(BCCH) definitely does express leucism. I have seen at least four leucistic BCCH in New England and there are publications about the phenomenon. Most of these express the trait in having partially to completely white heads.

All the Best & Good Birding,

Walter Ellison

Chestertown, MD

To view this discussion on the web visit https://groups.google.com/d/msgid/mdbirding/CAJCqPp2HtrK3JhokrbrhLFLwjAhot7V%3DC%2B6B2i4BFz-7jxoHww%40mail.gmail.com.

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Observing Nature is like unwrapping a big pile of presents every time you take a walk

[Gene Scarpulla]

Just a point of clarification --- I was speaking only about the Carolina Chickadee in the photograph, not Carolina Chickadees in general.

Gene

Bowie, Maryland

[Scott Young]

As I look into this mutation more, I have been told by Hein van Grouw that the Chickadee does not contain yellow-to-red pheomelanin so the brown color remaining is just less of the black eumelanin and relatively (or absolutely?) more brown eumelanin.  The chemistry of the melanins is still not entirely clear (certainly not to me) but I'm still searching!