I was at the beach this weekend and spent some time studying the various birds that fly around. I noticed some birds in flight move only their wings, keeping their body as still as possible, while others include more up-and-down body movement. Is this due to their size, or to their wing-to-body ratio, or am I just seeing things? Pelicans were the most still, flying long distances using just their wings. No head movement when flying straight. It was like if you took a video and blocked out the wings, it would seem like the bird wasn’t moving at all. Seagulls seemed to move their bodies a lot with the wing flaps, as did terns and ibises.
I’ve watched ospreys and they move body-wise more than the pelicans seemed to, so I wonder if it really is a ‘big’ bird thing?
Colibri, is there a term or classification for this? Do different bird types have the same propensity to move their bodies more or less?
I’m not sure exactly what you are seeing here. Most birds keep their bodies still and move only their wings when flying. In flapping flight, large birds flap their wings at a relatively slower rate than smaller birds. Also, large birds are able to employ soaring flight (in which they do not flap their wings at all), which smaller birds cannot do.
I’m not sure if it’s an optical illusion or not, but for instance, when a Canadian Goose is flapping, it’s body seems to move up on the down stroke, and down on the upstroke.
It almost looks like it keeps the bird’s center of gravity in the same plane.
I am not an expert in any are related to this, but it would seem to me that we are just talking action-reaction here. Birds with proportionally bigger wing areas would bob their bodies more as their bodies are not heavy enough to stay put as the wing pushes on the air.
Think of what would happen to you if you flapped your arms in air and in molasses.
What **Trunk ** says about center of gravity seems to click with what I mean. It looks like the pelican’s wing muscles are so strong that they don’t need to compensate with any body movement, where some other birds need to do that up and down thing that he mentioned.
Picture a kid on a swing, pumping his legs to get the swing higher. Leaning forward into the arc seems to help propel…that’s what I’m thinking of. it’s like the pelican doesn’t need to ‘lean’, his ‘legs’ do all the work.
If only I had a video to illustrate my point…