 On this page:
Color
variants
Deformed bills
Bald-headed birds
Other plumage variations
reporting unusual birds
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| Project FeederWatch began collecting data about plumage variations in 2000. Between 2000 and 2007, 1,605 Unusual Bird Forms were submitted, reporting a variety of plumage oddities in birds. Given that FeederWatchers report about 5.5 million birds each winter, a very, very small fraction of the birds being seen by FeederWatch participants have any kind of plumage variation. |
Lab volunteer Larry Newman created the pie chart at right, which shows that leucism is by far the most common oddity observed by project participants. Bill deformities were the second most commonly reported abnormality. The unusual bird traits are described below. |
Unusual Bird Reports 2008-2009 |
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| Percentage of each abnormality reported in the Unusual Bird Reports received during the 2007-08 and 2008-09 FeederWatch seasons. |
 Color
variants
When oddly colored birds show up at feeders, they can be difficult to identify. Most likely the birds are what they appear to be, only with some sort of color variation. If you see a strange-looking bird, use size, shape, and behavior to help identify the bird. Comparing the strange bird with other birds nearby can be helpful. |
| Albinism is the complete absence of melanin in the body, which results in completely white birds with reddish eyes, bill, feet, and legs. The redness comes from the blood vessels in the eyes and feet. Albinism is extremely uncommon. Leucism is an abnormal deposition of melanin. |
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Albino Rock Pigeon, photo by Herman Paulk, San Barnardino, California |
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There are two general forms of leucism--pale and pied. Birds with pale leucism have feathers that appear lighter than normal, as if the bird had been dipped in semi-opaque white paint. Birds with pied leucism have patches of white. Both varieties are often confused with albinism and are sometimes called partial albinism. |
| Leucistic pale Lesser Goldfinch,
photo by Barbara Tellman, Meadow Vista, California |
| The terminology for these abnormalities has changed over the years as scientists have gained a better understanding of the underlying causes. Learn more about leucism and albinism. |
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Leucistic pied Northern Cardinal, photo by Anne Page, Broad Run, Virginia |
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To further confuse things, occasionally a bird will lose feathers in a close call with a predator. When this happens the new feathers sometimes grown in white and then change back to the normal color at the next regular molt. This kind of white coloring looks like leucism but is not. |
| Carolina Chickadee with white tail feathers, probably from a close call with a predator. Feathers likely will be replaced with feathers of a normal color during next regular molt, photo by Vincent Smith, Phoenixville, Pennsylvania |
| Melanism, another color variation, refers to the excessive deposition of the pigment melanin, making extra dark plumage. As can be seen in the pie chart at the top of the page, melanism is seen far less frequently than leucism. |
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| Melanistic White-winged Dove, photo by John Pavesi, Cedar Park, Texas |
The color variation called Xanthochroism refers to yellowish or orange pigments replacing normal coloration, usually red. |
| Orange or yellow House Finches are often thought to have xanthochroism, but their color variation is actually diet based. Learn more about color variation in House Finches. |
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| House Finch with normal color variation, photo by Errol Taskin, Shreveport, Louisiana |
Deformed bills
Sometimes FeederWatchers observe birds with odd looking bills. A 1999 article in BirdScope first reported Project FeederWatch participants observing bill deformities.
Scientists are studying this phenomenon in Alaska, where the problem seems to be most prevalent. Colleen Handel, a biologist with the United States Geological Survey's Alaska Biological Science Center, has compiled reports of deformities in more than 25 species. |
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| Hairy Woodpecker, photo by Deb Apperson, Anchorage, Alaska |
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Deformities are reported most frequently in
Black-capped Chickadees. A cause for the deformities has yet to be determined. Learn more about Colleen's research.
From 2000 through 2006 Project FeederWatch collected 215 reports of bill deformities, representing 38 species from 38 states and provinces. As with Colleen's data, Black-capped Chickadees were reported most frequently, making up 30% of the reports. |
Black-capped Chickadee,
photo by Bonnie L. Long,
Anchorage, Alaska |
House Finches were reported the second most frequently with 21% of reports. The majority of bill deformity reports came from Alaska--31% of all reports received, while 12% of reports came from California, the state with the second highest total. FeederWatch is providing summaries of reported bill deformities to Colleen to assist in her research.
Bald-headed Birds
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Birds missing all of the feathers on their heads are observed most frequently in the late summer and early fall. The most common cause is likely a molt pattern where all of the feathers are replaced simultaneously (staggered feather replacement is a more typical pattern). Learn more about bald-headed birds.
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| Bald-headed Northern Cardinal, photo by Mary Ann Scott, Frankfort, Kentucky |
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