Quote:Considering the proportional area of a wing to a body usually seen in earthly birds, I had been considering these two possibilities as essentially the same.
- 4 wings together - well, I'm not seeing that this winds up being so very much different than a two-wing structure, though it probably allows you to do a few things (specialization into propulsion and lift, for example) that would not otherwise be available. On the pro side, you can run with a generally sinous body, maintain a relatively long tail (possibly flattened/flanged into a lifting/guiding body, particularly if the lift wings are near-stationary when in place) and travel along the ground as a snake. It also lets you play coatl, which is always fun.
- 4 wings apart, rigid - might work okay in the sky (I'm certain there are issues, but it depends on exactly what you're doing, and I don't have the grasp of aerodynamics or structural engineering (biological) to tell you anyway. On the ground, having a significant length of your body be rigid without the motivator limbs to walk around with is going to be not your friend.
Hm. Dual wingbeats potentially equals twice the beat frequency? Very good thing for eagle-sized or better.
Hybrids in the sense of clawed feet/hands, as seen in pterosaurs and (to a lesser degree) bats, yes, though I wouldn't be surprised to see some slithering and galumphing going on... leaving aside the ones that only land on water. I suspect that they would be more capable on the ground than bats are, though, as their wings wouldn't necessarily have a connection between each other to get in the way of their range of motion. Which is saying more than you'd think.
Takeoff for smaller species I picture as basically crouching down then using the main flight muscles to drive a hop straight up or a bit forwards (SPROING!) before starting to flap normally on the way back down. Larger types would jump with one set of wings while starting their first upstroke with the other, and the really big ones would likely need either a convenient cliff or a long stretch of open water to get into the air.
I doubt that any of the dragonfly birds I mentioned would be very big, no - maybe hawk-sized at best.
Quote:With four wings, you get:
Once you've got that, you have to think abotu what, exactly, this second set of wings is buying. What can this critter do with four wings that it could not have done with just two, and is that somehow a big enough advantage to overwhelm the associated disadvantages?
- Flight (if four's what you have, four's what you work with...)
- Improved performance envelopes (a wing that doesn't have to serve every purpose in your life can be better at a given thing)
- Improved multiclassing (versatility is a survival trait)
- Less 'wasted' weight (legs, while useful for many things, do not aid flight)
- Redundancy (a bird with one out of two wings broken is fucked vs a ground-adapted predator. a bird with one out of four is having a bad day.)
You pay:
- Additional set of flight muscles, and associated metabolic costs. (This would be my candidate for the killer; muscle isn't cheap)
- Decreased ground-level speed and maneuverability. (I don't think that this would take that big a hit.)
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