Whistling at night summons the ghosts.
Background information (Why does the informant know or like this piece? Where or who did they learn it from? What does it mean to them?):
I was always musically inclined, so I would always whistle at night, and I would always get the reminder from my grandma. They use it in a lot of Asian movies. So every time I guess I watch some of those movies, I would be reminded of my grandma or vice versa. I’m now very self conscious of whistling at night, even today.
Context (When or where would this be performed? Under what circumstance?):
I remember when I was in Taiwan once, I was whistling in an elevator at night, and two elderly women who I didn’t even know told me. It’s kind of a universal thing, everyone knows it. It tends to be among older people though.
This warning seems like an attempt to soothe the rambunctious behavior of younger children. Easily swayed by the threat of a ghost, kids may stop their unwelcome behavior of whistling late at night. The informant mentioned that members of older generations are more likely to bring up this proverb. They may have been a child when Taiwan was a more dangerous place, and police may not have existed in small villages. Not only is it rather loud and obnoxious, whistling may also call attention to a child and increase the chances of a kidnapping to occur.