Wikipedia:Reference desk/Archives/Science/2017 July 10

= July 10 =

Ground locomotion of birds
Today I saw a sparrow hopping and a pigeon walking. That got me to wondering—is there a pattern in bird taxonomy that predicts which ones hop and which ones walk? Or is there some other determining factor such as weight or the general environment they're adapted to? I couldn't find this out from our articles on locomotion or birds. Loraof (talk) 01:38, 10 July 2017 (UTC)


 * Then there's the odd-looking method of walking some birds use, where they hold their head stationary while walking, then jerk it forward, and repeat the cycle. This seems to be necessary because their vision system can't cope with movement of the eyes particularly well.  In particular, their ability to detect objects in motion is compromised when everything is in motion, relative to them.  As for hopping versus walking, is it just a matter of size ?  It seems to me that small birds tend to hop while larger birds walk or run.  (Of course, there are large mammals which hop, like kangaroos, but they have massive leg muscles, which would interfere with flying in a bird.)  StuRat (talk) 05:49, 10 July 2017 (UTC)


 * What birds are you referring to that keep their heads still and move their bodies forward. Richard Avery (talk) 07:37, 10 July 2017 (UTC)


 * Pigeons, for one. Matt Deres (talk) 15:48, 10 July 2017 (UTC)


 * And chickens. (I got to watch them a lot this weekend.)  Dad remarked that all their head motions are jerky, even when their feet are not moving; I said well, I guess, when your head muscles are adapted for staccato … —Tamfang (talk) 16:45, 10 July 2017 (UTC)


 * Yes, the same problem applies when they turn their head. If they did it slowly, they wouldn't be able to detect motion during the turn, so they do it quickly, so as to minimize the time when their vision is impaired.  Sort of like how we blink, for the same reason.  But apparently one thing a bigger brain does get us is the ability to detect relative motion even when our heads are moving.  And not just us, but birds with larger brains seem able to do this, too.  StuRat (talk) 17:25, 10 July 2017 (UTC)
 * Stu. Don't post your opinion and intuition as fact, please. This is all quite wonderful and fascinating speculation to you, I'm sure. But it's also all amateur guesswork, and completely inappropriate for a reference desk. For references that actually describe our knowledge on the topic, look at chicken cam image stabilization, e.g. here  or here  or even look at the scholarly literature on head-bobbing in chickens,  . Why make thing up? Especially when even a casual search on google scholar gives plenty of good references on the topic. Please research and include references when posting. Your guesses are well-intentioned I'm sure, but not helpful, and in this case misleading. You know better by now. You can do better. I know you can ;) SemanticMantis (talk) 01:23, 11 July 2017 (UTC)


 * Almost all birds can and will do both, walking and hopping, depending on their mood and situation. Some birds even dance sometimes! Some dance formal and slow paced, some like going wild. I think the determining factor is their default stance/degree of aggression and that shure fits our view of the peacefull pigeons. --Kharon (talk) 08:36, 10 July 2017 (UTC)


 * It has to do with energy conservation. Birds do whatever gets them what they want with the least expended energy. Smaller birds tend to hop because it uses very little energy and gets them where they want to go quickly. Larger birds tend to walk because it requires less energy to do so. There are exceptions. Further, birds who spend most of their time foraging in trees tend to hop because walking from branch to branch is hard. Birds who spend most of their time foraging on the ground tend to walk. . I personally believe it has to do with society as well. I live in South Carolina. We have sandpipers. They run quickly from place to place. When I was in Bermuda, I noticed that their sandpipers hop instead of run. I'm certain it is a different type of sandpiper, but my gut tells me that the Bermuda ones hop because they see all the others hop. The Carolina ones run because they see all the other ones run. 209.149.113.5 (talk) 12:30, 10 July 2017 (UTC)
 * Great answer and references, thanks. But I have to weigh in on your last comment "...because they see all the others hop": I can find no evidence of any bird where a hopping species can be trained to walk, or a walking species can be trained to hop. Hopping vs. walking seems to be purely set by species, not culture/learning, as far as I can tell, and that is the perspective of the research I link below. SemanticMantis (talk) 14:11, 10 July 2017 (UTC)
 * I intended to make it clear it was my opinion and my opinion was completely unfounded. After searching, I found numerous resources claiming that sandpipers hop on one leg in colder climates. I was Bermuda in February, so it was colder than the South Carolina beaches. Perhaps if I go to North Carolina, I will find hopping sandpipers. 209.149.113.5 (talk) 14:51, 10 July 2017 (UTC)
 * All good, I was just offering a contradictory viewpoint. No need to strike out your text, you did make it clear it was speculation, and it might even be true! I'm a bit chagrined that I cannot (yet?) find a good reference that explicitly addresses my claim that that walk vs. hop is almost totally genetic, but I'm getting close. Here is the best work I can find so far on multiple gaits within a single species, discussing walking, running, and (out of phase) hopping in the magpie. It does casually mention that "most species use only one or two gait types," viewing these magpies as a bit of an outlier. This paper  has a very good reference list in the introduction, and says that "patterns of walking, running, and even hopping are conserved among birds". This would indicated that gait is a | conserved trait taxonomically speaking, i.e. that we'd generally expect many members of a given bird clade to share the same gait, though this does not rule out some members using derived gaits.  SemanticMantis (talk) 15:28, 10 July 2017 (UTC)


 * Here is a nice analysis of how bird morphology influences striding gaits. Hopping is not considered, but it does give good background on energetics, morphology and gait. As for hopping vs. walking, this recent research (2013)  finds that "Cervical movement capability is perhaps the single most deterministic factor in the bird's choice of terrestrial gait. [i.e. hopping vs. walking]" SemanticMantis (talk) 14:11, 10 July 2017 (UTC)
 * It would be interesting to see a proper study of the difference. Astronauts on the moon found it easier to move around by hopping. Dmcq (talk) 15:01, 10 July 2017 (UTC)
 * See the article Bird feet and legs. After they evolved the ability to fly, other kinds of locomotion such as walking, running, hopping, climbing, swimming became of secondary importance and these abilities evolved differently in various bird species. An essential hindlimb function is to accelerate when taking-off and to absorb the shock of landing. Further adaptations in specific bird species are to use the feet as "hands" (the forelimbs being reserved as wings) for manipulations such as grasping a perch or prey, pulling food apart, scratching the ground, building a nest, turning eggs, self preening, etc. Efficient ground locomotion became critical for survival only in the cases of birds losing the ability to fly which has occurred in many different birds independently, generally in situations of no ground predators or deliberate selective breeding by man. They include flightless domesticated Fowl (chicken, turkey, duck), penguins, and Ratites (ostrich, moa, emus,...). The pectoral muscles for flight decrease and the pelvic girdle for running enlarges. Blooteuth (talk) 15:05, 10 July 2017 (UTC)


 * may be we need some article, ground locomotion of birds, or at least some material in bipedalism specific to birds?
 * Gem fr (talk) 13:17, 11 July 2017 (UTC)