Why do pigeons bob their heads?
Can you in your infinite yet magnanimous wisdom explain something that's been troubling me for years? When pigeons bob their heads as they walk is it because their legs are connected to their necks or what?
Of course not. As any fool can see, a pigeon's legs are connected to its body--and it's a good thing, because the pigeon would look mighty funny if it were assembled according to the offhand anatomy you describe.
Basically the pigeon's back-and-forth head motion--not exactly a bob--helps it keep its balance when walking. The pigeon's legs are located pretty far astern, and if it kept its head forward all the time it would probably tip over. This would expose the pigeon to the ridicule of the community. Instead, what it does is move its chest forward in time with one leg, and its head forward in time with the other leg. Thus some weight is always trailing a little abaft the port beam, as we say. Many fowl have similarly peculiar gaits, because they cannot afford orthopedic shoes.
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You dunderhead, where'd you dig up that story about pigeons bobbing their heads to maintain balance? Any text of ornithology (Pettingill's, for example) will tell you pigeons, like most birds, have eyes on the sides of their heads, their vision's basically monocular, and they bob their heads for depth perception. Birds with front-faced eyes, like owls, have binocular vision, and, like people, don't have to bob their heads. Straight dope, indeed! -- Paul G., Chicago
Listen, you chump, it happens that I have had an intimate association with pigeons since my earliest days and I know everything there is to know about them, or pretty nearly, anyway. My father used to send me out to feed the damn pigeons in his damn pigeon loft all the time, and I want to know who you are going to believe, some stupid internationally famous ornithologist or me, veteran pigeon feeder.
I'll admit this Pettingill fellow may have something with this depth perception business, but it is my undying conviction that balance has as much to do with it. It is well known that pigeons, along with most other birds, have enormous fields of vision--they can see 340 degrees around without moving, owing to the peculiar construction of the eyeball and the way the eyes are placed in the head. The peripheral vision of each eye is so great that the two visual fields overlap, giving the pigeon a binocular field of 24 degrees when it looks straight ahead. So if the pigeon is walking straight toward, say, a tasty piece of corn, it does not need to bob its head to maintain depth perception.
On the other hand, like all bipedal creatures, its ability to maintain balance is a delicate thing, and since its "arms" are occupied being wings, it is not unreasonable to suppose that the back-and-forth motion of the head helps maintain balance. So there. See if I ever answer any of your questions again, punk.
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The diffuse speculation on the function of pigeon head movements recently aired in your column demands comment. Unfortunately, both you and your steaming ornithological detractor err grievously. The bobbing actually takes place to preserve monocular acuity. Here's how it works, swine.
For an animal with side-mounted eyes, forward movements result in parallax shifts (apparent motion of near objects relative to distant objects). Now, vertebrate eyes--and retinas--work much better with completely stationary images. So what happens is that the bird's body walks on while the head is temporarily left behind to stabilize the image. The head is then jerked forward at the start of the next step.
Owls and humans, by contrast, have front-facing eyes, and thus, no parallax problem while walking. Heavy-headed creatures with side-mounted eyes (pigs, cows), for which the avian solution is impractical, apparently were dumb to start with and have grown to enjoy parallax shifts. If the aforementioned blather continues, maybe you and your critic along with Pettingrill should consider having your eyes remounted to match your wits. --Martin S., Chicago
It's Pettingill, not Pettingrill, my son. Try not to get so excited about these things. In light of the fact that we now have three separate theories on why pigeons bob their heads, it is apparent that the definitive answer to this question continues to elude the great minds of this century. Unless there are any pigeons out there who wish to contribute to the discussion, we will leave this issue to future generations to decide.
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I read your column in the discarded alternative newspapers--of which, I might add, there is no small supply--that blow my way across the pavement. About the pigeon controversy--i.e., why pigeons jerk their heads when they walk--the answer is really quite simple. We do it because it feels good. --Walter Pigeon, Equitable Plaza, Chicago