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ANOTHER MYSTERY BIRD, Part 3

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By now most folks familiar with birds of the Carolina Piedmont likely will have guessed our Mystery Bird from Hilton Pond Center is a Common Grackle, although except for size and shape it hardly looks like one. If you still didn't get the ID, don't feel bad. Everyday birds with aberrational plumages have fooled lots of experts, too.

Common Grackles are in the Icteridae, the Blackbird Family--so you'd expect them to be black in color. (Regardless, not all blackbirds are black, such as meadowlarks, orioles, and the females of several species in which males ARE black.) And, to be honest, some Common Grackles are normally NOT black; plumage in juveniles (below right) is a dull brown color that is replaced by black adult feathers beginning several weeks after fledging. The grackle we caught this week, however, was definitely NOT a bird still sporting juvenile attire.

From a distance our aberrant grackle actually seemed lighter in color than it did in the hand, and it photographed even darker than it appeared to the eye up close. Nonetheless, it was far, far paler than the black of a normal adult Common Grackle (below), leading us to conclude it was a "leucistic" bird. Leucism, from the Greek word leukos--which gives rise to the English words "leucocyte" (white blood cell) and "leukemia" (too many defective leucocytes)--is a situation in which all the colors of a bird are much paler than normal. Our grackle was not a true albino, however, because albinos lack every pigment except their blood's red hemoglobin; this results in pink eyes, pinkish or orangish bill and feet, and, of course, all-white plumage.

Our aberrant Common Grackle definitely had color, but rather than the weakly formed feathers and dull, listless plumage of a juvenile grackle, the leucistic bird bore feathers that were well-constructed and rich brown--or we should say "browns" because of many different brownish hues. The bird's head and upper breast (below) were noticeably darker than the rest of the plumage and of a color that reminded us a little of the brown on the head of a female Eastern Towhee.

We were especially impressed by our bird's mantle--the portion of the back just behind the neck and between the bases of the wings. Here the brown was a deep, deep chestnut, with a hint of red. We must confess we spent a couple of minutes just looking through our camera's viewfinder at the breathtaking color of the mantle, and we regret the digital image simply couldn't capture the hue's true intensity.

Speaking of interesting shades of brown, we were also intrigued by the color of our leucistic grackle's bill and legs. In normally colored Common Grackles, the horny epidermis of these body parts matches the rest of the dark plumage, with the exposed tarsometatarsus (lower leg), toes, claws, maxilla, (upper bill), and mandible (lower bill) all being a shiny blue-black. (See color of bill in photo of normal adult above, and of normal leg and toes below right.) By comparison, the bill and leg of our leucistic grackle (below left) were an unusual brown that we can only describe as sensuous.

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We've only seen this shade of brown a couple of times before--in the leg and bill color of leucistic Ruby-throated Hummingbirds, in particular the one we banded several years ago in Chester SC (below), about 25 miles south of Hilton Pond.

What caused our unusual Common Grackle at Hilton Pond Center to be leucistic is anybody's guess, but like most things in nature genetics is likely a factor. And, if it is genetic and our leucistic bird mates--something that seems likely since we actually caught it in a trap with a normally pigmented grackle--it's possible its leucism will be passed on to offspring. We thought about all this as we marveled over our unusual capture, took its measurements, photographed it, and placed a lightweight numbered band on its leg before releasing it unharmed. And we thought about it again the very next day when a huge flock of Common Grackles descended like a dark shroud behind the Center's old farmhouse, and right in the middle of them was our leucistic Mystery Bird-- its shiny aluminum anklet glistening in the afternoon sun as it foraged for acorns just like a black grackle would do.

All text & photos © Hilton Pond Center
Juvenile grackle photo by Patricia Velte © Pat's Backyard Bird Cam

POSTSCRIPT. The leucistic Common Grackle AND the normally pigmented one we caught together in the same ground trap this week did have something else in common: Each was carrying a partly engorged tick on its crown. The one on the leucistic bird was only about 2mm long, but that on the normal grackle was already swollen to about 5mm. (The maximum size of ticks we've found on birds at Hilton Pond Center is about 7mm.) Based on info we've seen on various listservs and in E-mail from correspondents, the winter of 2005-2006 seems to have brought a bumper crop of bird ticks--at least in the Carolinas. If you have observed ticks this winter on birds at your feeders, or if you've found a dead bird with one or more ticks, please send an E-mail to RESEARCH. Include your name, city/state where the bird was found, the bird's species and sex (if known), how many ticks were on the bird, the specific site(s) of tick attachment, and other relevant anecdotal info. An upcoming installment of "This Week at Hilton Pond" will deal with the bird tick topic.

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Be sure to scroll down for an account of all birds banded or recaptured during the week, plus other nature notes of interest.

"This Week at Hilton Pond" is written & photographed
by Bill Hilton Jr., executive director of
Hilton Pond Center for Piedmont Natural History.

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