David Sibley explains what to look for the next time you see a partial albino bird

Feathers around the eyes and on the crown, nape, malar, and wings of this Slate-colored Dark-eyed Junco lack all melanin pigment, leaving the bird with pied plumage. White feathers can appear in any pattern on partial albinos but on this bird are clustered along normal feather tracts. Art by David Allen Sibley.
Feathers around the eyes and on the crown, nape, malar, and wings of this Slate-colored Dark-eyed Junco lack all melanin pigment, leaving the bird with pied plumage. White feathers can appear in any pattern on partial albinos but on this bird are clustered along normal feather tracts. Art by David Allen Sibley.

Sooner or later everyone who watches birds will come across a real oddball. Some of the more frequently seen abnormal birds are the partial albinos. They can be all white, have white patches (a white head, perhaps), or appear pale grayish tan all over. Many terms are used for such birds, but I prefer simply to call them partial albinos. (Leucistic means the same thing.)

View photo gallery of albino and partial albino birds.

A partial albino may be almost completely white, or it may have a few white feathers. On some birds, such as the junco above, the white feathers are clustered along normal feather tracts. On other birds, they can be scattered all over. This form of partial albinism, where normally colored feathers exist alongside white ones, I call pied.

Another common version of partial albinism, in which the feathers still have a little pigment, is called dilute plumage. The bird looks pale tan or gray and shows a ghost of its normal feather pattern.

Birds have two kinds of melanin pigment. One is a reddish brown to buff color and is responsible for the red breast of American Robin and the pale buff flanks of Black-capped Chickadee. The other melanin ranges from the black of crows to the soft gray of juncos. Most birds have both pigments; they work together to produce all black-brown-buff colors and, with the addition of carotenoid pigments (red to yellow), produce almost all of the varied colors of birds.

Each kind of melanin can be lost independently. An American Robin that is mostly white but has a more or less normal reddish breast is a bird that lacks the black-gray kind of melanin but retains the red-brown kind.

A loss of melanin can have many causes and may be permanent or temporary. True albinism is a genetic condition causing a complete absence of melanin, including pink eyes. Partial albinism is more common and can occur in healthy birds that are otherwise normal.

If you see a partially albino bird, ask yourself: Is it pied or dilute? Is it missing both kinds of melanin or just one? Much about its appearance can be explained by these relatively simple factors.

 

This article from David Sibley’s “ID Toolkit” column appeared in the January/February 2014 issue of BirdWatching.

 

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David Sibley

David Sibley

David Sibley writes the column “ID Toolkit” in every issue of BirdWatching. He published the Sibley Guide to Birds in 2000, the Sibley Guide to Bird Life and Behavior in 2001, and Sibley’s Birding Basics in 2002. He is also the author of the Sibley Guide to Trees (2009), the Sibley Guide to Birds-Second Edition (2014), and guides to birds of eastern and western North America (2016). He is the recipient of the American Birding Association’s Roger Tory Peterson Award for lifetime achievement in promoting the cause of birding and a recognition award from the National Wildlife Refuge System for his support of bird conservation.

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