Re: pterosaurs, bats, flying theropods (fwd)

[Michael Bruce Habib <mbh3q@virginia.edu>]

Do that many owls really hunt bats?  As far as I know, most 
owls do not hunt bats, and in fact, most owls do not take 
flying prey.  Their manueverability is moderately high, but 
not on par with Chiropterans.  They give up some 
acceleration to maintain silence, after all.  Great at 
silent drops after terrestrial prey, but not really falcon 
or accipiter-style aerial hunters.

Furthermore, owls are not particularly well adapted for 
striking fast aiborne prey because they _are_ limited by 
light conditions in regards to sight.  Keep in mind, most 
owls locate prey and track at distance by auditory cues, 
not visual ones.  Good eyes are useful when there is some 
extra light, or at very close range (when closing).  Since 
they don't actually ecolocate, this tracking strategy works 
best on prey in contact with a surface.

There are also many diurnal raptors that preferentially 
hunt in heavily forested areas, accipiters are the most 
notable.  Many eagles do as well, but they're not as 
relevant to this discussion.

There are many more species of Falconiforms than 
Strigiforms, as well (over 300 vs only 180 or so).

Just the same, I agree that the presence of owls 
suggests that avoidance of predation is not the only 
factor involved.  The differences in sensory equipment 
between Chiropterans and birds lead to competitive 
differences besides predation, which may be more important

> All this discussion of diurnal raptors applying pressure to make bats
> nocturnal, ignores the fact that there are nocturnal raptors, too: owls.
> Curiously, the fact that bats have a speed disadvantage and a
> maneuverability advantage might work to their advantage in daylight (all
> other things being equal), because among flighted predators, the fast strike
> is the preferred method of attack. If a prey animal can dodge that, it has a
> very good chance of outmaneuvering the raptor in a longer chase. See ducks
> and pigeons versus peregrine falcons, and rabbits vs. red-tailed hawks. I'm
> not familiar with any diurnal raptor that will preferentially hunt in
> scrubby or heaviiy forested areas like owls will, either. Why didn't bats
> simply move into denser habitats, more suited to a dextrous flyer?
> Obviously, some of them did. Curiously, owls are very maneuverable flyers,
> as well as being silent and able to see in conditions that are as close to
> pitch blackness as nature provides outside of a cave. This is what lets them
> prey on bats.

Mike Habib