The expression “blind as a bat” indicates a general belief that bats are either totally blind or unable to see very well. This creates a common misbelief among people that bats can’t see. I did some research myself and found out the truth.
So, are bats actually blind? No, bats are not blind despite the fact that bats generally use echolocation to navigate. In fact, researchers show that sometimes bats rely more on their eyesight than echolocation for hunting. Fruit bats or flying foxes sleep at night and use their eyesight in the daytime to find the flowers to drink nectar from.
This idea probably arose because many bats avoid bright sunlight and fly primarily at dusk or night. But some bats are quite active during the day and some species, like the fruit bats or flying foxes, sleep at night and do practically all their foraging by daylight.
Actually, even the night-flying species have excellent eyesight in semidarkness and can see reasonably well in broad daylight.
I have occasionally seen bats flying during the day and they obviously could see where they were going. I have also seen large numbers emerge from their roosting quarters while the sun was still bright and at least one daylight migratory flight of many individuals has been observed.