2/5/11
Hi John,
I was somewhat startled to notice in Lincoln's pix today the pale color of Pale Beauty's tail -- very light red, even white towards the top, where it meets her body -- and wondered whether this was a normal variation among RTs, or a function of her age? I.e., as she gets older, will her tail darken to the same intensity as PM's, or do you think it will remain as it is now?
Best,
Mai
2/5/11
Mai,
Thanks for bringing this photo to my attention. I hadn't seen it. And yes, this feather is uncommonly light-colored.
The feather, which falconers call a central deck feather, right in the middle of the tail (ornithologists call tail feathers "retrices"), still has rusty hues, but it is markedly lighter than normal. Is this normal? Maybe. Maybe not. There is a moderate chance that Pale Beauty, like a good number of Red-tails, has genes for leucisticism (formerly, and incorrectly, "albinism").
A very few Red-tails, from before hatching, are authentic albinos, birds unable to synthesize any tissue pigment. They are pure white in all feathers, and have whitish eyes. Only a few of these have ever been studied, and they appear to have a number of other physiological problems, resulting in their early deaths. Very few, if any, of these true albinos ever survive to adulthood. Pure albinism in many animal species is related to a host of other biochemical defects.
But among all the Buteo hawk species in the world, it appears that the Red-tailed Hawk is most commonly leucistic. I trapped and studied one and observed two molts before it was released. There are now many Internet postings of photos of leucistic Red-tails. They are seen each autumn at all the major hawk migration points, such as Hawk Mountain.
From field reports of their occurrence here in Ohio, I estimate that one Red-tail out of every 1000 to 5000 displays leucistic feathers at some point in its life. And the following relates to Pale Beauty. l hypothesize, based upon my field and lab observations, that the leucistic trait is expressed much in the manner of gray-headedness in humans; it is not much seen, or only in low intensity, in early age. But as the hawk with the gene(s) gets older, more and more feathers molt out white.
And in the first stages of Red-tail leucisticism, in most cases, only large flight feathers are first affected. In Pale Beauty's case, her central retrice sure looks to have the gene. There just isn't much reddish pigmentation.
So this could be really interesting. If she really does have leucistic genes---and the paleness of her head, too, might give a hint of that---we just might see a partially white tail feather a year from now. Two or three years from now, a good portion of the retrices, and probably some wing primaries or secondary, will molt out white.
Often, there is a curious pattern of unpigmented white against normal pigmentation, all in the same feather. Half of it, often in an angled, slashed pattern, is white, with the rest normal.
Now clearly Pale Male, if he has leucistic genes, has not expressed them. At his age, he'd be angelic white if he had a full complement of leucistic genes. But I'm very curious about Pale Beauty's weakly-pigmented central tail feather. It may be a hint of something to come.
And of course, what might be the feather pigmentation, then, of new Pale Male/Pale Beauty eyasses this year, if either---OR BOTH---have Red-tail DNA for white feathers? This could be very interesting.
Or, Pale Beauty's weakly-pigmented tail feather may be merely incidental to some other, non-leucistic genes. That feather may drop down in next summer's molt with normal pigmentation. Hope we can watch this.
--John Blakeman
