Sunday, February 21, 2010

Forensic Conjecture

At long last arrives a day warm enough for out-sitting and for drawing inspiration from its largess. So generous has this day been with birdsong, it would be hard to choose the music of only one species about which to write. Instead, with gratitude, I pause long enough to notice the variety, the buoyancy, and the understated exhilaration of the birdsong of early spring---whether it stems from the joy of first warm days or the sexual excitement that comes with the arrival of mating season.

Before I can begin again to reflect on the ever new noticings that reward my return to the backyard, I must tie up an unfinished blog topic described on November 7 & 13, just prior to my long absence---that of the mystery of the half-bird carcass.

My daughter, Hannah, shared the mystery with one of her graduate school professors who is an ornithologist in the field of environmental education. After some Q&A e-mails, Dr. Lisa Zinn conjectured the carcass to be that of an unhealthy tufted titmouse, and I learned more from her two e-mails than from a week of observing and wondering about the unfortunate bird.

I learned, for instance, that birds re-grow all their feathers every year; that asymmetry in bird feathers indicates a mutation, or illness, or injury; and that a stray white feather and white legs both indicate loss of pigment and lack of good health.

Dr. Zinn's response takes the educational value of this blog up a notch, that's for sure. AND, excitement of excitements for an amateur birder, she has invited me to participate in a bird-banding at the time of Hannah's graduation. Wahoo!

She has also graciously granted permission for me to post her e-mails in this blog. Below is a cut-and-paste of our e-mail exchange via Hannah. I reversed the order so you don't have to scroll to the bottom to read backward. Start at the top and read down in correct sequence:

hey mom--i read your blog and sent the part about your half a bird to lisa my birding professor and thought she would know but she has a million more questions. :) this is her response:

I read your mom's blog and I don't know right off what the bird was. I need a little more info. The most important being size. I am confused by her first thinking it was a mocking bird and than a Tufted titmouse because they are very different in size. Can you find out how big it was? Also, how white were the legs? Could they have been considered light blue? How yellow was the beak? Was it yellow on the top and bottom? She said it had a yellowish breast, how yellow was that? Was it just off white or distinctly yellow? Also, was the white outer tail feather really just one feather or several feathers? Heh! I guess that is a lot of questions. If you could just find out about the size and the legs (and maybe the beak) that would help.

Fun---and all good questions. It was an interesting muse for blog, but I would hate for Lisa to spend a great deal of time on it. Only if she can ID from the description, with no extra research. Not that important!

Size: I almost addressed in the blog the absurdity of not being able to distinguish between titmouse & mockingbird, for the very reason Lisa suggests---the disparity in size---but didn't want to go on too long. I really couldn't tell what size it was, however, because only the lower belly and legs, lower back and tail were left--- a partial lower curve of the body. The soft under-feathers on the belly and on the back under the wings were fluffed, which might have made it look larger than it was. We first thought the tail looked long, but later decided it was an optical illusion----partly because we were so close, and partly because the tail made up most of what was left. To put a measurement on it , I'd estimate it to be about four inches from where it originated to tip.

Tail: It was a definite V shape (even more defined than that of a titmouse), not rounded, or pointed (as in mockingbird) --- the white feather(s) was only on one side, making it asymmetrical in color, which I did not understand. It was not the outer feather, but maybe the second or third one in----closer to far left side than center, and the feathers on the right side of center were all gray. (maybe it was a politically liberal bird :-) All I could see was the left edge of the white feather, as the tail was not spread. It looked like a white stripe that ran the length of the tail and was about 1/4 inch wide, slightly narrower at the top, and widening toward the tip. It could have been more than one, but looked singular to me. As I type this, it makes me wonder about a Carolina Chickadee, but that, too, seems too small for this carcass. Soft back feathers at point of tail's origin were a pale gray.

Yellowish underbelly: These feathers were fluffy and almost exactly the color of the belly or sides of a tufted titmouse, sort of a pale yellowish peachy color---or maybe a warbler of some variety?

Legs: White---Possibly could be interpreted as light gray or blue, with buff or tannish colored feet. Legs and feet seemed too long for titmouse, but wondered if it was because they were thrust out in an unnatural position. Feet were definitely more tan than gray, and darker in shade than the legs.

Beak: Was wide open and I could only see the interior----like two triangles edged in yellow, black interior, but probably due to decay----about 1/2 inch sides of the triangles---the tip was a little wider than 45 degree angle, not quite 90 degrees. Seemed shorter and wider than I would have expected---more like a nestling's beak. But I've never actually observed the inside of an adult's open beak :-) Also, too late in year for nestling. I was too squeamish to look directly at it for long---and though I wanted to flip it with a stick, couldn't bring myself to touch it even indirectly. The flesh that was left on the head was too messy to describe and gives me the heebie jeebies to recall it! (had to scrunch my face to type this)

A good puzzle for a Sunday afternoon. Love, Ma

Ok, this is some interesting information. I will respond point by point.

Size: I completely understand how different bird sizes look up close as opposed to at a distance. There is definitely an optical illusion that happens with bird sizes. However, the 4 inch tail length is a very good clue and is about titmouse size.

Tail: The forked tail can also be a bit deceiving. Almost any bird tail can looked forked if you move the feathers apart for each other a bit in the middle. We have had trouble with this in bird banding because there are a few species where you have to look for a forked tail but it is pretty hard to tell when you are up close if it is genuinely forked because you can make it looked forked or not forked depending on how you move the feathers around. It is good to know, though, that the tail wasn't pointed and the tail feather's were not rounded. The information on the white tail feather was very interesting. The fact that it was not symmetrical changes everything! This is most likely not the color that feather was supposed to be but rather a mutation. Birds re-grow all their feathers every year and it is not unheard of for a bird in poor health to grow a white feather instead of the appropriate color. Birds also re-grow lost tail feathers so it could have lost that feather due to injury and the one that re-grew was white.

Legs: The fact that the feet were also darker than the legs makes me further suspect that this was not a healthy bird. It sounds to me like it was under a lot of stress and was unable to produce the required pigments for it's legs and it's feather. Either that or it had a mutation from birth that caused it to lack some pigment.

Summary: My best guess is that this was a rather unhealthy tufted titmouse that showed clear signs of stress. Perhaps that cat put it out of it's misery :)

Thank you, Dr. Zinn!

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