Bird Bones

Bird Bones

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The shoulder, arm, and hand of a bird

When I was a kid I was always admonished not to feed chicken bones to the family dog. Why is that?

Birds have hollow or semi-hollow bones with an internal structure of supporting struts. Physics tells us that a hollow tube is harder to bend or break than a solid tube of the same material and diameter. So bird bones are overall stronger than mammal bones because they are denser, which makes sense since flying and landing require strong bones. The corollary to this, though, is that when bird bones do break, they tend to shatter and splinter while mammal bones tend to break relatively cleanly. So if a dog chews on a chicken bone, the bone may shatter, producing sharp shards of bone that can puncture a dog’s throat.

According to the Scientific American, “For centuries, biologists have known that bird bones are thin and hollow. Yet bird skeletons don’t actually weigh any less than the skeletons of similarly sized mammals. To sort out this seeming discrepancy, Elizabeth Dumont of the University of Massachusetts Amherst studied the skulls and limb bones of song birds, rodents and bats. And she found that, on average, bird bones are the densest, with bat bones coming in a close second.”

The humerus and ulna, the arm bones that hold the flight feathers, are roundish in cross section. This also strengthens them; you can demonstrate this to yourself by breaking a flat toothpick in half and doing the same to a round one.

You have probably seen mammals such as deer or raccoons, and certainly dogs, that have been crippled by some injury, or have even lost a leg. How many crippled or one-legged birds have you seen? Probably not many. If a bird has a broken wing, it will not be able to feed or escape from predators and will die rather quickly. Breaking a leg can also be very serious, but I have actually seen a number of one-legged birds that seem to be surviving just fine, many of whom were shorebirds. In Hawaii, I have discovered, many doves are missing toes. Apparently, according to the ornithologist at the University of Hawaii, doves walk on the beach and get human hair from sunbathers wrapped around their toes, cutting off circulation.

But take a look at this “one-legged” Willet video http://www.youtube.com/watch?v=0stDhtaNgJo which might surprise you.

I get lots of e-mails from people who have found an injured bird and want to know how to rehabilitate it. I always recommend that they contact their local wildlife rehab center or veterinarian. If it has a broken bone, only a vet can treat it successfully. The bird may be able to survive with a broken bone, but only in captivity. In Chico, you can call the Bidwell Wildlife Rehabilitation Center at 343-9004 for advice or help. You can also go to Ornithology.com’s bird rehabilitation page or Wild Animal Rehabilitation for information on what to do with sick, injured, or baby birds.

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