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At 11:30 AM 28/02/01 +0100, Jarno Peschier wrote:
Maybe in reality that's the other way around? Birds already existed (let's
assume that bats evolved later than birds even thought that's probably far
from 100% certain) and already had good eyesight so they primarily dominated
the day time. Bats had to try and do their stuff at night to avoid direct
competition with the ever present bird during the day. This in turn was a
strong selective pressure that caused the bats to quickly "develop"

Let's not forget that not all bats echolocate, and some birds do. The echolocating birds (swiftlets and the oilbird Steatornis caripensis) breed in caves, as do many (but not all) echolocating bats, and apparently do not use echolocation to find food (swiftlets are diurnal and the oilbird is a fruit-eater). Though not all echolocating bats are cave roosters, it is at least possible that echolocation evolved in both groups as an adaptation to living in caves and only later, in the Microchiropteran bats, became useful for food-finding (and reached the level of sophistication seen in bats; echolocating birds use a lower (audible) frequency which I gather is less precise at object discrimination and does not have the added property of being able to "jam" insect hearing systems). This idea would allow for the early stages of echolocation in bats to have a functional role in a less precise form; I believe that the only megabat to echolocate is also a cave-dweller that does not hunt by echolocation, though as I am not at home I cannot check on this.

Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2 mailto:ornstn@home.com