Aerodynamic Considerations
Most bats have lower wing loadings than do birds, and he mentioned that this difference may be due to the way bats forage. Most insectivorous birds forage by making repeated, short flights. Bats, on the other hand, remain on the wing for most if not all of the time they are foraging, and insects are captured by virtue of bats' ability to maneuver rapidly. In birds, the slots formed by the alula and primary flight feathers allow these animals to have high wing loadings and fairly low stalling speeds. In the unslotted wings of bats, the wings do not yield such refinements in flight characteristics, but within the size and wing loadings of bats there is little need for increasing lift. In comparison, the flight of bats is much is clearly less efficient than that of birds. The upstroke consumes relatively more power in bats than in birds because the wing surfaces in bats are continuous and do not allow the passage of air as do the spaces between the primaries of a bird.
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