Birds with abberant plumage are one of the more common oddities we see at the Rouge River Bird Observatory. Abnormally-colored feathers are fairly frequent, and some examples are below. Two outstanding examples have their own pages: an intergrade Yellow-shafted/Red-shafted Flicker, and a stunning white-breasted American Robin. Abnormal feather growth is also sometimes encountered, with a few examples on the next page.
Plumage that is abnormally white
An an abnormal reduction in the deposition of pigment in the feathers is known as leucism. Some leucistic birds appear entirely washed out or pale if the reduction of pigment is roughly equal in all feathers (some authors now call this “hypomelanism”). More often, pigment is absent in only some feathers, and this is known as pied leucism, or “partial amelanism.” Causes include genetics, or injury, disease, or malnutrition.
Once or twice a year, we see an American Robin (Turdus migratorius) that has several white feathers or patches of white feathers. This one was photographed by Darrin O’Brien on 29 Apr 2009 at a Dearborn office complex.
This unusual American Robin was banded on 7 Oct 2007. It was an adult female undergoing its fall molt. The breast feathers were normal. However, nearly all of the incoming feathers on the wings, tail, and body that are gray in normal robins were full or partially “frosty” looking.
Typically when abnormal white feathers are seen on birds, the entire feather is white, as in the first example. Partially white feathers like this are something RRBO encounters only rarely, and not to the extent found on this bird.
A leucistic Yellow-rumped “Myrtle” Warbler (Dendroica coronata) was found at the on campus from 15 to 17 May 1997. The wings and tail of this bird were entirely white. Soft yellow was visible where most yellow-rumps have bold yellow on the flanks. The back and head were pale gray, and some pale gray streaking replaced the prominent streaking of normal-plumaged yellow-rumps. This bird appeared to be a male. While relatively common in some families of birds, abnormally pigmented individuals are rare in the Parulidae (wood warblers).
This sighting was documented in the following paper:
Craves, J. A. 1997. Extreme leucism in a Yellow-rumped Warbler (Dendroica coronata coronata). Michigan Birds and Natural History 4:199-200.
Here is another example of a leucistic Yellow-rumped Warbler, from Florida.
Plumage that is abnormally orange
Carotenoids are the pigments responsible for most of the red and yellow colors in birds. They cannot be created by birds without dietary input. Thus, the pigments in what birds eat can influence the color of their feathers. If a bird consumes particular deep red pigments while feathers are in active growth and also has yellow plumage, some or all of the yellow feathers may turn out to be orange. This is most frequently seen in the terminal tail bands of Cedar Waxwings (Bombycilla cedrorum), which are normally yellow. About 5% of the Cedar Waxwings banded by RRBO have had orange terminal tail bands (right). It was first noticed in the 1960s, and it has since been confirmed that it is due to waxwings consuming the fruit of introduced Morrow’s Honeysuckle (Lonicera morrowii), which contains a red pigment called rhodoxanthin. This honeysuckle is common at UM-Dearborn.
A number of other bird species have been recorded with orange or reddish feathers in place of yellow feathers that could be attributable to ingestion of rhodoxanthin. The White-throated Sparrow (Zonotrichia albicollis) at right was banded by RRBO on 27 September 1998. This bird has orange-colored lores rather than yellow. Subsequently, RRBO has banded two more White-throated Sparrows with orange lores, and this phenomena has also been reported by other banders.
The first record was documented in the following paper:
Craves, J. A. 1999. White-throated Sparrow with orange lores. Michigan Birds and Natural History 6:83-84.
Tricks Exotic Shrubs Do: When Baltimore Orioles Stop Being Orange (pdf) by Tom Flinn, Jocelyn Hudon, and Dan Derbyshire — article from Birding magazine.
Occasionally we have encountered Northern Cardinals (Cardinalis cardinalis) that are very vividly colored or with some orange plumage. The male on the right was banded by RRBO on 25 October 2000. It had patches of orange feathers, and several wing feathers that were orange. This abnormality may have been caused by a lack of some sort of dietary pigment that left the normally red feathers less intensely red. Dietary deficiency of certain carotenoids is responsible for orange- or yellow-colored House Finches (Carpodacus mexicanus).
Perhaps some lack in the diet combined with ingestion of a red pigment like rhodoxanthin that contributed to the orange color as well as the crimson color of the red plumage. Other orange cardinals have turned up in the literature and on the Internet, beginning in the late 1990s, lending some credence to the role of honeysuckles and rhodoxanthin in this plumage variation.
An ‘orange variant’ Northern Cardinal. Hansrote, C. and M. 2000. North American Bird Bander 25:1-3.
And now, a white/pink cardinal! Ohio Birds and Biodiversity.
The yellow cardinal lives on. Ohio Birds and Biodiversity.
RRBO has banded a half-dozen Ruby-crowned Kinglets (Regulus calendula) with at least some orange crown feathers rather than salmon red, all since the year 2000. Examples of two individuals are shown below. This may also be due to a dietary deficiency.
Abnormally dark plumage
When birds have plumage with excess pigment, usually the dark melanin pigments, they are known as melanistic.
This Mourning Dove (Zenaida macroura) was seen in the Dearborn yard of Julie Craves and Darrin O’Brien on 8 Apr 2006. The second photo shows it compared to a normally-colored Mourning Dove.
The first secondary feather on one wing of this American Goldfinch (Spinus tristus), banded 20 Aug 2010 was completely black on the underside, rather than having a white base. When melanism occurs, it seems that it typically affects all feathers. RRBO has not documented a single melanistic feather or patches of melanistic feathers on any birds, much less the thousands of goldfinches banded on campus.
More information on abnormal plumage coloration
Davis, J. N. 2007. Color abnormalities in birds: A proposed nomenclature for birders. Birding 39:36–46.
David Sibley’s web site: Abnormal coloration in birds: Melanin reduction.
British Trust for Ornithology’s Abnormal Plumage Survey page.
Abnormal feather growth on next page.