Why Bats are Nocturnal?

As usual due to my nature while wandering in surrounding just picked up line from a group of persons sitting around road in one corner, " He is just like a bat, we cant trust him?" My ears flinched and mind gushed, "why they compare him with bat?" So just halted and pocked my nose into their conversation. I failed to make out anything about "The Bat Story" . I just moved away from that place with a question hitting my mind constantly. What is common between mistrust and Bat?

Days after I come across this story told by one old man about this. Here it goes like this...

"Long time ago, Their was a great war between Animals and Birds. Birds was winning and bats joined birds saying that they are also Birds as they fly like them?

After few days animals side advanced in fight and gain some advantage in war. Bats left Birds side and joined Animals. Saying that They are also Animals as they give birth to babies and breast feed infants like animals.

Again Birds gained some edge in war and similarly bats left Animals and started proving their loyalty to Birds.

As war continues for long time, no side comes out to be clear winner or powerful, Advancement kept swinging between both side and also Bats keep on changing their side.

When war stopped after mutual understanding between two side. Then role of bats also come into light. Both Animals and Birds banished them from their society.

Since then Bats become Nocturnal and symbolically represent man with cunning and cheap attitude.