Posted at the request of John Blakeman. Interesting follow-up about the
leucistic Red-tail Hawk and a request for 'Citizen Science'.
If you are a photographer John would like more photographs of this hawk (in
the CVNRA) to identify eye color.
Regards,
Adam & Matt Valencic
Chagrin Falls, OH
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From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Saturday, September 20, 2008 10:44 PM
To: [log in to unmask]
Subject: Re: [Ohio-birds] FW: [Ohio-birds] Light colored hawk (Zebra Hawk!)
CVNRA
Adam,
Please post this, if you might.
I just examined a full-density copy of the photo of the zebra red-tail, and
discovered the following.
First, there is no doubt that a portion of one of the retrices (tail
feather) is fully and typically red. This means that the bird is at least in
its second year. As everyone knows, red-tails don't get red tails until
they've molted away the brown tail feathers they left the nest with.
By now, late September, virtually all red-tails have completed the molt of
their tail feathers. Close examination of some birds in September will
reveal that two or four tail feathers are still "in the blood" and
descending to full length. But the brown first-year tail feathers will all
have been lost.
More important with this bird is the hint in one silhouette photograph is
the bird's iris color. Instead of the dark brown iris of a red-tail in its
third or older year, I detect a lighter hue, suggesting that the bird is in
it's second year.
If the bird has a yellow iris -- and I'd strongly ask observers of the hawk
to see and report if this is so -- this will tend to authenticate my
contention that leucistic red-tails are probably normally colored in their
first or second years, with the feathers become less pigmented with each
ensuing molt.
Again, I know of no photos of leucistic red-tails with this curious,
half-white, half-dark color pigmentation. This may well be a bird right in
the middle of transformation from normal color to the much more, mostly
white pigmentation of typical leucistic red-tails. If it has a light-colored
iris, instead of the dark brown iris of older birds, this could be one of
the only birds observed in transition at this young age.
Does leucisticism appear in young red-tails, or, does it appear at age, in
the manner of gray hair in humans? I've always presumed the latter. If this
bird has a yellow iris, indicating that it's a young adult, the trait
appears much earlier.
I hope birders in the CVNRA can keep track of this interesting hawk.
And then, it will be interesting to see if it mates this winter and begins
to breed with copulation and a nest in February and March.
I'd also like to learn of the bird's sex. It appears that most leucistic
birds are females. Back in the early 70s, I watched a female leucistic
red-tail nest and produce a single tiercel (male) eyass, which was normally
colored. We banded the eyass and returned it to the nest in Sandusky County,
west of Fremont. I had numerous reports of locals taking shots at the bird,
so with my scientific collecting permit I trapped it in August of the
following year. We kept it for a full year at Bowling Green State
University, where we wanted to notice its molting pattern. Curiously, a tail
feather that was entirely white when trapped was replaced with a feather
partially red. This pigmentation variability was noted in a few other
feathers.
Finally, the bird was released in a state to the west, where it was much
less likely to be shot.
Fortunately, very few red-tails are being shot by poachers any more. Because
red-tails are very seldom shot or illegally trapped in recent years, they
have now saturated all available good nesting habitats. Consequently,
first-year mortality of red-tails is now very high, probably approaching 80%
or more.
And while I'm running on here, let me state that it's so unfortunate that
Christmas Bird Counts and other similar population surveys have failed to
tally adults and immatures. I believe that today there are far fewer numbers
of late summer immature red-tails in Ohio. With habitat saturation by old
adults, rising immatures tend to starve in July and August. Today, it's
tough to be an inexperienced immature red-tail. It would be helpful to have
adult to immature ratios from previous decades, or even now. Just why hasn't
such helpful and obvious data been collected?
Age ratio data should also be accurately collected and recorded for the bald
eagle. Sooner or later it's going to run into the same problem young
red-tails have. Eventually, the multitudes of fledged bald eagles will fail
to find un-occupied territories or habitats, after the state becomes
saturated with territorial adults.
Of course, bald eagles are quasi-social, and unmated immatures can hang
about in large winter gangs. But just what will be the fate of Ohio bald
eagles when the state can no longer support any more immatures? Plotting
annual adult to immature ratio changes of both red-tails and bald eagles
could really help predict where things might end up at territorial
saturation. With red-tails, I think we're there. An unmated young red-tail
now has no open place to live a normal red-tail life. Someday, that will be
the case with bald eagles, too. Watching the age-ratio changes from year to
year would be helpful to accurately characterize this modern conservation
success.
Sincerely,
John A. Blakeman
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