posted August 5th, 2011; last edited August 13th, 2011 –– David Sibley

Abnormal coloration in birds: Melanin reduction

Albino and partial albino birds

A full (or true, or complete) albino Northern Cardinal, recognizable by the lack of pigment in the eyes, making them appear pink. see below for discussion. Original gouache painting copyright David Sibley.

The presence of white feathers on a normally dark bird is the most frequently seen color abnormality. Every birder can expect to encounter white or partly-white birds with some regularity, and the more striking examples will stand out even to novices.

All black and brown coloration in birds comes from melanin (of two types). Birds create melanin pigments using an enzyme, and this melanin is deposited in the growing feathers by color cells. At any stage and for many different reasons this complex process can break down, leading to a variety of conditions:

  • an inability to produce melanin and complete absence of melanin throughout
  • an inability to deposit melanin in the feathers and an absence of melanin in some or all feathers
  • a lack of one type of melanin (many possible causes), leading to an absence of that type while retaining the other
  • a failure to fully oxidize the melanin leading to a change in color from blackish to brownish
  • a partial loss of one or both types of melanin (many possible causes), and therefore a lower concentration of melanin in the feathers

Through careful study birders can sometimes deduce the cause of the abnormality, but different conditions can produce nearly identical results. Conversely, the same condition in different species of birds can produce very different results.

Terminology

There has been some recent discussion about the proper terminology for these conditions (Buckley 1982, Davis 2007, van Grouw 2006), with competing proposals from aviculturists, ornithologists, and birders. One of the reasons for the disarray is the lack of a simple “umbrella” term for all conditions involving the reduction of melanin. Birders cannot be expected to analyze each odd bird and choose the proper term to apply to that particular form of melanin reduction, and this leads to misuse of technical terms. I propose that the term “albino” is already in popular use and has become the default name for the category. Birders should continue to use the terms “albino” and “partial albino” to refer to any bird with abnormally white or pale feathers. When you look at a swirling flock of blackbirds and see one with a white tail, or one that is pale tan all over, it is OK to say “partial albino, flying left!”

A true albino is a very specific genetic mutation, rarely seen in the wild, and can easily be referred to by calling it a “full”, “true” or “complete” albino. The other terms mentioned below (leucistic, dilute, etc.), and others, can be used for specific cases, but consider all of the possibilities and be wary of false precision.

The term leucistic has a confused history. In the introductions of the Sibley Guides I said the term leucistic is synonymous with dilute plumage. That usage was fairly common among birders at the time, and I was unaware that it contradicted several scholarly publications (e.g. Buckley 1982, van Grouw 2006) which define leucistic as the total lack of melanin from some or all feathers (what I called partial albino in the guides). It does make sense to distinguish birds that are unable to deposit melanin (my partial albino, their leucistic) from birds that are able to deposit melanin but only in low concentrations (my leucistic, their dilute). Below I’ve used the term leucistic (not partial albino) for birds which cannot deposit melanin, which helps to distinguish these birds from the narrowly-defined true albino, and allows use of the term “partial albino” as a general category for any bird showing any form of reduced melanin. These terms should be corrected in the introduction of the Sibley Guides.

The True Albino

A full or true albino (see illustration at the top of this page) is a very specific mutation with a well known genetic cause similar across all vertebrates. These birds are unable to produce melanin at all because of the absence of the required enzyme tyrosinase. All of the plumage is white and the skin is unpigmented. Even the eye is unpigmented, and appears pink or red as we see the blood vessels in the retina. Melanin serves some critical functions in vision and in protecting the eye from UV radiation, so full albino birds can’t see well and for that and other reasons don’t survive long in the wild. Adult full albino birds are essentially never seen in the wild. Note that the inability to produce melanin does not affect the red carotenoid pigments, so the red color appears more or less as usual on this bird’s feathers and bill. An albino bird is not necessarily all white!

The normal Cardinal

A female Northern Cardinal with entirely normal colors. The plumage color is a combination of black/gray eumelanin, chestnut/buff phaeomelanin, and red carotenoid pigments. Original gouache painting copyright David Sibley.

Fully leucistic

A fully leucistic Cardinal lacking all melanin in all feathers. Original gouache painting copyright David Sibley.

These birds can produce melanin, so the eye appears black, but something prevents them from depositing melanin in the growing feathers. The red carotenoid pigment is unaffected so the feathers are red in all the normal places for a female cardinal. Note that in any of the numerous species that lack carotenoid pigments (e.g. Song Sparrow, Herring Gull, Blue Jay, American Robin, etc) exactly the same underlying condition – a total lack of melanin in the feathers – would result in completely white plumage.

Partially leucistic

A partially leucistic Cardinal lacking melanin completely in some feathers, while other feathers are normal. Original gouache painting copyright David Sibley.

This is probably the most commonly seen plumage abnormality in wild birds. This mutation is extremely variable in appearance, as birds can have just a few white feathers scattered on any part of the body, or whole sections of the body white, or the entire body white (fully leucistic, above). The white feathers are often grouped in feather tracts, so that most of the head is white (as shown here), or some of the wing coverts are white, or most of the tail, etc.

Lacking eumelanin (Non-eumelanic)

A female Cardinal completely lacking the black/gray pigment eumelanin, this leaves only the rufous to buff phaeomelanin pigment (and red carotenoids). Original gouache painting copyright David Sibley.

The most obvious differences from the normal bird include the lack of the blackish face and the greatly reduced pigment in wings and tail leading to very pale wingtips and tail tip. This condition is rare, and can be very similar to some dilute plumage conditions. Note that in a species that lacks the chestnut/buff phaeomelanin pigment (crows, many gulls, etc) this same condition – a lack of eumelanin – will result in completely white plumage.

Lacking phaeomelanin (Non-phaeomelanic)

A female Northern Cardinal completely lacking the chestnut/buff-colored pigment phaeomelanin. Original gouache painting copyright David Sibley.

It retains the normal dark gray eumelanin in the wing and tail color, and the dark face, but the body feathers appear quite abnormal. They lack all of the warm buff tones of phaeomelanin, leaving only pale and plain neutral gray. This condition is rare. There is no bird known that has only phaeomelanin pigment, it is always found with eumelanin, so this condition will never result in an all white bird.

Dilute plumage

A female Cardinal showing dilution. Original gouache painting copyright David Sibley.

Melanin of one or both types is produced and deposited in the feathers, but at low concentrations. The resulting pale gray-brown pigment is very susceptible to fading, and these individuals quickly become bleached by the sun. In dilute birds the relative concentrations of melanin on different feathers often remain the same as on normal birds, but all are much paler so the bird shows a faint “ghost” of the normal pattern. This is particularly striking on strongly-patterned species such as raptors or immature gulls, where the dilute bird will show the typical pattern (e.g. tail bands, etc.) but all in a faint pale brown. Many dilute birds have about 50% of the normal concentration of melanin. The palest dilute individuals can be nearly indistinguishable from fully leucistic birds, especially when bleached and worn.

Not illustrated here:

  • a mutation that leads to incomplete oxidation of the blackish eumelanin, so it is deposited in the feathers as a slightly paler brown color and is very quick to fade. This is obvious when it occurs in species like crows, but far less obvious on a Cardinal.
  • a condition known as grizzle, in which feathers are not uniform but have varying concentrations of melanin, partially dark and partially pale.1
  • an inherited condition known as acromelanism, in which feathers grown on warmer parts of the body (e.g. the chest and belly) are less pigmented than feathers grown on colder parts (e.g the top of the head).

And there are other variations, with other causes, too numerous to be mentioned in a brief overview such as this.

Conclusion

The coloration of birds is simple in some ways, and marvelously complex in other ways. Birds with abnormal plumage can be strikingly beautiful or just unusual-looking, and they can provide a fascinating deductive challenge as we try to figure out just what is going on.

References

Buckley, P. A. 1982. Chapter 4: Avian Genetics. in Petrak, Margaret L. (Ed) 1982. Diseases of Cage and Aviary Birds, 2nd edition. Lea & Febiger, ISBN 8121-0187-1

Davis, J. N. 2007. Color abnormalities in birds: A proposed nomenclature for birders. Birding 39:36–46.

van Grouw, H. 2006. Not every white bird is an albino: sense and nonsense about colour aberrations in birds. Dutch Birding 28: 79-89.

Notes

  1. Note that grizzle is not to be confused with the pale-based flight feathers seen in some juvenile crows and other species. That is apparently a temporary condition caused by environmental issues (presumably health and diet). It is not a mutation and the same bird will grow normally-pigmented feathers in its next molt. []

22 comments to Abnormal coloration in birds: Melanin reduction

  • Joseph Morlan

    Thank you for using a common sense approach and bringing clarity to the increasingly contentious subject of abnormal plumage terminology. I agree that “albino” and “partial albino” are easily understood, while other terms such as “leucistic” are not. When it comes to the sometimes inherent conflict between being arguably correct and being understood, I come down on the side of being understood.

    But what terminology do you propose for birds which have extra melanin? These are often called “melanistic,” but I have seen this term used for dark morph birds in which the extra pigment is part of normal variation. I don’t think this is correct or likely to be understood. A dark morph Red-tailed Hawk is not really melanistic because its plumage is part of normal variation. I prefer to use terms like albino or melanistic only for birds which have some disorder which is outside normal or expected variation. Would you agree with that?

    And what does it mean to be be partially melanistic? I’ve seen this term used occasionally and never understood it at all.

    • Hi Joe, Good question. I’ve wondered the same thing. Is the underlying mechanism of white morph birds like Reddish Egret similar to any of the causes of “abnormal” plumage, such as leucism? We consider a white Cardinal “abnormal” because it is rare, and white Reddish Egrets “normal” because they are common, but they may have similar origins. I don’t know, maybe someone reading this can help.
      I’m working on some other posts on plumage abnormalities, including melanism. That’s much less common, except in species with a dark morph, and I’ll be looking into the question of whether we can make a distinction between abnormal and normal.

  • Martha R Carpenter

    Partial Albino American Robin, in my backyard, Eureka, CA (Humboldt County). From my bedroom I can watch the many robins who come to eat cotoneaster berries in February. This morning, I was surprised to see this bird, with both black and white feathers on its back. It had the usual robin’s red breast. The black and white seemed rather random, no particular pattern, but it was pronounced. The closest I have seen (online) was a Pied Kingfisher in Southern Africa. There were about thirty robins in all, but only one was black and white. He was obviously healthy, and I could see nothing else unusual about him. Sorry I couldn’t grab a photo, but he was gone before I had time to get the camera. 2/28/12

  • I live in No. Illinois. We just had, what appeared to be a bird the size of a blackbird, with a brown head and the back of the bird was a faded mustard yellow color going all the way to the tip of his tail. He had a beak like a blackbird. I have checked bird books and online, but I can’t find out what it was. I’m going to try to get a pic of it. It was at my feeder along with sparrows, cardinals, bluejay, and blackbirds.We just experienced a windstorm yesterday with 60 mph wind gusts. I thought maybe he blew in with the storm :) Help!
    Balisha

    • Hi Balisha, This doesn’t sound like any normal North American bird, so I think you are on the right track that it is probably an abnormally-colored bird lacking some melanin. If you see it again do get some photos, and try to pay attentionto its size and shape and how it acts. If it’s a blackbird with abnormal color it will still be the same size and shape as the other blackbirds, it will travel with them, and it will act the same way. Let me know how it turns out.
      Cheers, David

    • Possibly an immature Orchard Oriole? Just a guess. I have seen solitary orioles follow birds to feeders before. I had an immature male Prothonotary Warbler eating seeds one August. I would love to see a pic of your bird, too.

  • William Young

    Dear Mr. Sibley

    I live in Northern Virginia, and a female cardinal who is missing phaeomelanin has been frequenting a neighborhood park in Alexandria. I have shot some video footage of her and put it into a video called “Gray Girl,” which I uploaded to YouTube. The link to the video is:
    http://www.youtube.com/watch?v=IaKnTev-S44

    I am always amazed that whenever I have a question about a color abnormality of any species of bird, I discover that you have already written about it. I very much appreciate the work that you do.

    Best
    Bill Young
    Arlington, VA

  • I caught what I think is a fully leucistic Curve-billed Thrasher. It was taken in central Arizona. I check my oddities against Google images and unlike the very numerous Northern Cardinal, I only found a few examples of the CBTH with leucism. I was very very excited to experience this bird. I put three sample pictures on the website.

    • Hi Matt, Nice photos! and an interesting bird. It looks like it has a fairly uniform reduction in melanin all over, being almost white. I’m guessing by the eye color and the obvious yellow flanges on the gape that it’s a recently fledged bird, and therefore in juvenal plumage. The lack of color could have many different causes, and this bird might molt into a more normal adult plumage soon, or not, either way would be interesting to document if you have a chance for more photos. It does seem like some common species – like Robins and Grackles – are more often albinistic. I’ve always wondered if that’s just because we see a lot more of them, but there do seem to be real differences in frequency between families of birds.

  • I thought that the website would be shown in the approved comment. Here is the website for those of you interested:

    http://www.whatbird.com/forum/index.php?/topic/4194-curve-billed-thrasher/

    Thank you very much for your comments David. I will attempt to capture the bird again. Hope mom and dad don’t chase it off.

  • Miriam

    BS”D

    hello David,
    i enjoyed reading about the mutations very much! i do have a question though that i’m hoping you can answer~ is there a way that someone can intentionally produce an albino or leucistic bird from normal parents..
    thank you,
    miriam

  • Lorie

    Thanks for this information. Recently (3/31) a friend and I were observing a female northern cardinal at my feeder. However, she had a LOT of red on her breast mixed with brown farther down. There was more red on the wings than the normal female would have. The mask around the eyes was black but the area beside the bill and under it was a grayish color like the black hadn’t come in. It’s not an immature male according to several birders. It looked like a female except for this excess red.

    Up until recently, I never even considered that the birds would have color aberrations aside from albinos. Of course I know better from this article.

    We have also had the appearance of a slate-gray junco with a white bar across its shoulder and a white spot on its head (also near our feeders).

    • Hi Lorie, Interesting! The amount of red that females produce can vary a lot, depending on the hormones at the time the feathers grow. Females with more testosterone produce more male-like feathers with more red, and disease can cause a female to produce less red. It sounds like the bird you saw also had some albinism, with less black than usual, although the dark mask on normal females can be grayish in parts.

  • Phil Johnston

    For the last month, we’ve watched a pair of “normal” northern cardinals feeding/tending a pair of fully leuclistic offspring. Both white birds have the charateristic black eyes, pinkish streaks on wingtips, crest and tail but are strikingly white otherise. They are also far more “skitish” than ordinary cardinals at the feeder. I wonder how often this anomaly affects more than one nestling?

  • So many of these cardinals show up displaying bilateral male/female coloration that I have to believe
    they are males with one defective teste and not true gynandromorphs or hermaphrodites.
    More likely just signs of leucism.
    I do find it interesting that the male pattern is always on the left side.

  • For the past 2 years I’ve been photographing an incredibly beautiful bird at my feeder. This morning I emailed photos to a friend, who passed them on to a couple of experts that immediately identified her as a partially leucistic cardinal. She then sent me a link to this article and I was overjoyed to read about my mystery bird. She continues to be a source of pleasure and amusement and now she has a name! Thank you.

  • I have a question relating to my previously posted comment. I photographed this cardinal in August feeding another bird that I assumed to be her baby. The young bird was gray-brown and white at the time. What are the chances of a baby having the same mutation as the mother?

    • A few years ago I read someone’s analogy that trying to figure out a bird with white feathers is like diagnosing a car that won’t start – something is going wrong but there are many possible causes among several unrelated systems, and you can’t tell from the outside. In this case it seems like the color abnormality must be genetic and passed from parent to offspring. Usually that is not the case, but it does happen.

  • Mary Dryburgh

    I have a slim, slightly smaller than usual crow coming by for dog kibbles. He is bolder than most and has white feathers on his breast and down his breast bone and a white patch on both of his greater secondary coverts. I thought he was simply leucistic until I saw the wind blow his chest feathers and the there is a large patch of bright red skin exposed. Scare tissue? Wound? What do you think? It will be awhile before I can point a camera at him I should think.

  • Michelle Hayden

    For the past two years I have had a female fully leucistic cardinal feeding at my feeders. I am so glad I found this website. Now I know what she is.

  • Carol Johnston

    I’ve had a female at my feeder this year and it’s white all around the eyes. It looks like she has a white mask. I’ve noticed numerous cardinals that are discolored in different areas. Is leucism found more in cardinals than other birds?

  • Joel G Sanders

    South side of Santa Fe, NM
    On Sunday afternoon November 2, 2014 (light rain) there was what I assume was an inca dove feeding on the ground and the coloration was not as shown in book, but was a beautiful all over light warm (reddish-tan) white. The only variation was on the primaries, which were very slightly darker, and secondaries were a little lighter than the primaries. There was no marking on the remainder of the bird–just the very light warn white — not albino which I would describe as an absence of any color whatever. The bird was around for about 15 minutes, but when I went to get the camera, of course it vanished.
    Joel G. Sanders

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