Saturday, December 2, 2006
Saturday, December 2, 2006
Posted by Bill of the Birds at 12:56 PM
Sitting, waiting for the birds to get used to the large creature intently watching them, I began to notice the habits and appearance of individual birds. The Carolina chickadees, tufted titmice, and white-breasted nuthatches are the brave souls who return first to the feeders after I've moved into position and scared everyone away. I noticed that the bravest of the titmice had a feature that made him/her/it a marker bird--an overgrown upper mandible. Marker birds are individuals that have some sort of physical trait that allows you to tell them apart as individuals--a bald cardinal, a one-eyed house sparrow, etc.
This type of minor bill deformity is not uncommon in birds, but it's interesting to see. And I might not have noticed it had I not been creeping up close to take pix of our feeder birds. There are many theories about the cause of such a physical anomaly--poor diet, some sort of injury event, a kink in the DNA, or as the result of contaminants in the environment. There are studies being conducted with black-capped chickadees and other species to determine the cause of these deformities.
Our little TUTI seems to be getting by just fine. The overgrown portion of its bill looks thin enough that it might wear away or even break off while a sunflower seed is being pounded open.
So that's your obscure fact for the day about bird bills from Bill of the Birds.
We have another marker bird around the feeders this winter, a dark-eyed junco with a pale head. This type of abnormally pale or white plumage is frequently (and incorrectly) referred to as "partial albinism." The correct term is leucistic or leucism referring to a reduced amount of the normal pigmentation in plumage in birds and other animals. Albinos are completely lacking in pigment. An albino bird would be pure white with pink soft parts (bill, legs, even eyes).
Our junco has a splotchy pale head, but seems to be completely healthy and normal otherwise. I've taken about a dozen images of it during the past two weeks.
But we humans are not the only ones who notice marker birds...
I remember going to visit a purple martin colony in Williamstown, WV, with my mom's bird club, way back in the early 1970s. The colony was huge and thriving, living in big, wooden martin houses along the Ohio River. In the colony there was a single albino martin. This individual bird was incredibly easy to see, not only because it stood out amid all the dark, normal-plumaged martins, but because its colony mates would not leave it alone. They constantly dive-bombed the albino, trying to force it away from the colony. From their instinct-driven perspective this made sense. A white bird would be more likely to attract a predator, such as a Cooper's hawk, to the colony. And maybe the other martins simply perceived this white bird as a freak that did not fit in.
I remember being very sad about this. I felt sorry for that albino bird who just wanted to live among his own species. He may not have even known he was different. How sad is that?
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