Butter, it's very easy to identify the flying motion of bets. Bets' flight is not so as steady as birds do and their flight is not a straight line. In my own words, I will say when a bird flies, you know where it wants to go roughly but for bets you could hardly predict what it will go since the flight is quite circular.
Also, under traffic light or other similar light sources, the wing section is much more translucent.
Lucky that it's still very common to see bats, since my childhood. I hope Hong Kong citizens can observe more around their surroundings and understand we always live with nature. Wild life is not just pests. They are very interesting indeed.
