By Jeremy Schwartz
Have you ever seen a ghostly white bird come to a bird feeder, or perch in a tree near you?
Or maybe one that is only partially white, in blotches over its head, chest or back. An American Robin, for example, its normally bright orange breast mottled with white, like it had an unfortunate encounter with a bottle of bleach?
Perhaps this bird looked like it was wearing a white sheet, with its lower body normally covered.
For the most part, birds like this are not sick, nor do they have one clawed foot in the ethereal plane. Birds that have spots of white or are mostly white, instead of their normal plumage, are called “leucistic.”
In honor of Halloween, I wanted to take a little bit of a closer look at this condition, given the ghostly appearance it can sometimes lend the birds it affects. I’d also like to explain the difference between leucism and true albinism, which may be what most think of when they spot an all white or mostly white bird.
Leucism in Birds
Leucism is a genetic condition that prevents the color pigment melanin from correctly depositing in feather structures. In some cases, this defect can weaken flight feathers, making it more difficult for affected birds to escape predators. This, combined with the how easy a splotchy white bird is to see in a tree or bush can increase the chances of it getting eaten. One more strike against birds with this condition? Some research has suggested that leucistic males of a given species can have a harder time finding a mate. Tough break.
Leucism is generally pretty rare. Project FeederWatch, a program run by the Cornell Lab of Ornithology, logged 1,605 reports of odd or unusual looking birds at feeders in North America between 2000 and 2007. Though the numbers were not broken out to call out reports of leucism specifically, that 1,605 “odd birds” number is out of 5.5 million birds reported each winter in that same time frame.
According to the British Trust for Ornithology’s ongoing Abnormal Plumage Survey of birds in backyard across Britain, 82% of 3,000 records of abnormal plumage reports submitted have been classified as leucistic. Overall, British birders who’ve submitted to this survey recorded 58 individual species as being affected with leucism.
Leucism vs. Albinism
True albinism, while sometimes confused with leucism, is much easier to tell. Albino birds (and any animal, really), lack melanin in their bodies, too, not just in their feathers. True albino birds will be completely white (except perhaps for orange/yellow coloring on their feathers, as this color is not based on melanin) and sport pink or red eyes. The lack of eye pigmentation allows the bird’s blood vessels to show through, accounting for the red eye color.
Albinism can be similarly detrimental to the effected bird, as it completely negates any camouflage the bird would have with its normal plumage. An albino bird would also likely struggle with feather wear and deterioration, just like with leucistic birds, as melanin plays a roll in strengthen feathers. Plus, albino individuals of any species (including humans) typically struggle with eye site problems.
So, though both instances of a white or almost-all-white bird showing up at your house are rare, any bird you do see that appears unusually white will likely be leucistic, not a true albino, as the site Birds and Blooms describes. Albino birds just don’t live that long.
Leucism In Your Backyard
The detrimental effects on the bird notwithstanding, spotting a leucistic bird in the wild or especially coming to your backyard feeder can be a thrill.
In the realm of bird-list keeping, jotting down that you’ve seen a leucistic American Robin or Crow (like in the lead image for this post) can feel like you’ve added a one-of-a-kind item to your collection. Even among the same species, no two leucistic birds will look the same.
Though Backyard Birding, includes no leucistic birds, any species featured could potentially be affected by this condition. So while you're out making the most of your Halloween season, keep an eye out for any birds that look like they may be dressed up for the occasion.
A version of this post originally appeared on my Medium page.