I used to think that hummingbirds had to flap their wings to keep their heart beating. So, I would run around the yard and make sure that they didn't land, so they didn't die.
A childhood belief about birds

others believed things like this
- When I was five or six, I was worried that I'd lost my heart because I didn't hear it beating.Anon
- I used to believe that you shouldn't swallow gum because it would stick to you heart and make it stop beating.Anon
- I still believe that if I really concentrate, I can stop my heart from beating.— Patrick
- I used to believe that airplanes would land in your yard and pick you up.— Rachel
- I used to think that
"The land of make believe"
was
"The land of baked beans."— Baked Bean! - My daughter thought bumblebees were baby hummingbirds. — Carolyn