My colleague Steve Pruett-Jones called my attention to a remarkable phenomenon: an albino ruby-throated hummingbird (Archilochus colubris; the only native hummer that breeds east of the Rockies). These photos are from DiscoveryNews, and were taken in Virginia. The bird appears to be a true albino since it has pink eyes.
Albinism, seen in many species of animals, results from the inability to synthesize the pigment melanin.
I imagine being white will be selected against in the wild. I’ve linked below to a story that says kiwis have a rare recessive allele that causes whiteness when homozygous (again not thought to be albinism):
http://www.stuff.co.nz/environment/6175929/Birth-of-second-rare-white-kiwi-remarkable
Oops, shouldn’t have said “again”; should’ve read your post more carefully.
Wow – that’s spectacular!
The ruby-throated hummer is not the only hummingbird to breed east of the Rockies. The black-chinned hummer breeds in Texas, New Mexico and parts of Oklahoma – all east of the Rockies – and is expanding its breeding range easdtward.
That would be south of the Rockies. It seemed obvious to me that Jerry was referring to the northern part of the US, since going further south guarantees a whole lot of other hummingbirds, irrespective of where the Rockies might be.
Better check a map, Thanny. Northern Texas and Oklahoma are east of the southern Rockies, and Black-chinned Hummingbirds breed east of the Rockies as far north as southern and central Colorado as well. Virginia, where this bird was photographed, is in the southern U.S.
Maybe he meant east of the Smokies?
Beautiful!
There was a story recently on Auntie about a non-albino white crow somewhere …
Blackbird, not crow.
Exquisite!
“Leucistic” perhaps, but since the beak is a decided yellow colour, I doubt that it’s albino. Beaks are made of something like keratin, and in the rotted-down and mounted bird skulls that I’ve seen, they’re a translucent-white. (“Dad, why is there a bag in the freezer labelled ‘Barn Owl’?” “Why, Son, it’s because I want to try to skin and mount that one, not just rot it down for it’s skeleton. When I’ve time.” I shrugged, and got lunch out of said freezer, while my sisters rolled eyes at the ceiling. Perfectly normal conversation.)
So, even if the bird has lost the ability to make melanin, it seems to still have some pigment-making ability, even if only a yellow pigment. Though I’ve got a suspicion that yellow in birds is produced by low quantities of melanin.
As a side issue – if it formed no pigments, it’d be dead ; haemoglobin is a pigment, thought it’s not used because it’s a pigment.
Thinking of the chemistry, would all biologically workable oxygen transport chemicals be pigments? I suspect so – to reversibly bond oxygen, you need to do things with lone pairs of electrons that are likely to lead to visible-spectrum energy level changes. But I’m (almost) interested to hear of counter-examples. Decapod crustaceans use a copper-based oxygen transport compound, which happens to be a blue-red pigment too.
leucistic is a reduction in all pigmentation whereas albinism, or more helpfully hypomelanism, is a reduction in melanin.
http://en.wikipedia.org/wiki/Leucism
If I’m correct then we’d expect to see normal pigmentation in the eyes if this specimen were leucistic (e.g., Piebaldism).
Anerythristic means lacking red, yellow, and orange pigmentation.
In reptile and fish breeding circles an animal that is both albinos and anerythristic (black albino) are called ghosts.
You might want to check your monitor’s color balance, Aidan. This bird’s bill is pinkish, as is typically the case in albinistic hummingbirds, and for the same reason that your fingernails are pinkish.
Hummingbirds’ bills consist of a thin keratinized sheath over vascularized tissue and living bone. When the sheath is uncolored by melanins and/or carotenoids (which in birds are responsible for most red, orange, yellow, and pink colors and contribute the yellow component to most greens), the pinkish color of the underlying tissue shows through the translucent keratin and becomes the color of the bill.
Jerry, vhutchison is correct that Ruby-throated is not the only hummingbird to breed east of the Rockies. Besides Black0-chinned, Buff-bellied nests in southern Texas, and several other species nest in the mountains of western Texas. “East of the Mississippi” or “east of the Great Plains” would be more accurate.
Weird Yet beautiful, thought albinos only existed in humans.
Surely you’ve seen domestic white rats, rabbits, mice, to mention just a few?
Like several folks wrote, the hummer is probably leucistic. The photos seem to show a dark iris. Leucistic animals usually have blue irises and a yellowish tinge. Leucisticism is a genetic change effecting pigment expression similar to melanism, (black leopards)I think. Melanism is not usually detrimental but leucisticism usually is. This creature is absolutely exquisite.
It is exquisite, but also much very hard to understand. The green color of the Ruby-throated Hummingbird is caused by the combination of a yellow pigment and a blue structural color, an interference color caused by tiny ridges that are spaced so that reflected blue light waves reinforce each other, while other colors get jumbled rather than reflected.
This means an albino hummingbird should be iridescent blue. How did this one lose not only its pigments but its structural color? The only explanation I can think of is that the microscopic ridges that cause the structural color must be made of melanin or other pigment molecules. In that case the hummingbird’s inability to produce pigments would also remove the structural color (or shift it into non-visible wavelengths).
Lou, greens originating from a combination of melanin-based structural blues and carotenoid-based yellows occur in parrots, jays, and many other birds, but in hummingbirds greens are produced entirely by melanin-based iridescence. That’s why pigment abnormalities have produced normal-eyed budgies with blue, gray, and black and white plumage (axanthism), red-eyed budgies with yellow and white plumage (amelanism), and red-eyed budgies with entirely white plumage (albinism) but no blue or yellow hummingbirds.
Crawford Greenewalt’s Hummingbirds is an excellent resource for understanding the anatomy and optics of hummingbird iridescence.
Nice to have an expert commenting here. 🙂
Someday I hope to move to a more hummer-rich region so I have an excuse to buy your books.
Hi Sheri,
Yes, I was thinking it was like the budgies, but really it is more like trogons and quetzals, with no pigment at all, pure interference colors. This makes the albinism all the more mysterious. Are the physical structures that cause the interference made of melanin? That is the only explanation I can think of for an albino hummingbird being white instead of green…
Yes, melanin-based structures are responsible for the green iridescence in hummingbirds (platelets) and trogons (platelets in quetzals, rods/tubules in other species).
Thanks for that info!!!!
Hi Jerry, just as an FYI, I’ve written a post on the free will debate at Rationally Speaking, responding to your recent exchange with Massimo.
The Attenborough interview is excellent, thanks for posting.
Amazing finding. There is a report of albinism in bats, check out the link.
http://eprints.bicmku.in/66/1/4._BA%26GM-CS2004.pdf
The N.C. Aquarium in Fort Fisher has a resident albino crocodile.
http://picasaweb.google.com/118024945607403925351/Vacation_2010#5483552674118629410
That is incredibly cool-looking!
Albino plants also occur, but they don’t live long:
http://www2.gi.alaska.edu/ScienceForum/ASF4/433.html