Tuesday, March 10, 2009

How a bird's neck works

There seems to be a need to clear up some misunderstanding here about how a bird's neck "stretches." A living bird's neck does not stretch; a bird with a stretched neck is a dead bird. Below is a generalized avian skeleton, linked to from Enchanted Learning (thank you, Google!):

And here is a hummingbird skeleton, linked from Hilton Pond Nature Center:

Notice how the neck is held in a curve. To "stretch" the neck, this curve is straightened. To "retract" the neck, this curve is tightened. You can of course see this much more obviously on herons; it works the same way on all birds, the feathers just conceal the process more. Just like on a turkey or chicken neck, the skin is tight up against the narrow bands of strong muscles; it is not baggy and stretchy. So, when the neck is "stretched" there is not much actual stretching happening. There is no pull on the breast or mantle skin, the breast and mantle won't be drawn up into the neck. They are quite independent in their motion. If anything, there might be some slight compression of skin at the base of the nape, which could push the upper mantle feathers slightly rearwards if it affects them at all. There is also an absolute limit to how far the neck can extend. Once it is fully extended that's it; nothing the bird can do can make it any longer than that.


At 4:45 PM, Blogger emupilot said...

While you know alot more about bird anatomy than I do, I will be more convinced by an accurate distance measurement. The preening Red-headed theory seems far-fetched based on the shape of the bird and your analysis. Still, since with the photo's resolution it is not possible to tell if the bird is looking away (IBWO) or away and up (aberrant Pileated), I'm willing to cut a little slack in the plausibility department to someone who thinks the head might be turned toward us and down.

As measured, the size of the mystery bird is already about the same or larger than the Pileated, and I expect that an accurate measurement to the mystery bird's tree would if anything be greater than that reported by the pin finder thanks to intervening vegetation. If the distance were the same or greater that would eliminate Red-headed, but if it were less it could confirm Red-headed. Until that measurement comes in (and as necessary I think surveying equipment could be used to measure it by parallax), I won't rule out Red-headed.

At 4:54 PM, Blogger cyberthrush said...

"As measured, the size of the mystery bird is already about the same or larger than the Pileated..."

do I misunderstand you or are you mispeaking Emu.? -- as initially measured by Gary the mystery bird's size is SMALLER than a PIWO -- THAT is one of the main confounding problems here. If it was a hasty, imprecise measurement than it may indeed change (of course skeptics will cry 'foul' if it does), but that is what hopefully may yet be resolved.

At 4:59 PM, Blogger emupilot said...

My interpretation of the diagram on the right on the tracing page indicates that if an appropriate tail length is used, the mystery bird would be about 10% longer than the Pileated if the Pinseeker distance measurements (61 mm vs 56 mm) are correct. If I am reading that wrong, then I stand corrected.


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