At the school I first attended, there was an enormous privet hedge with several big gaps in it, presumably where the branches hadn't been able to grow or where the hedge had been damaged by a football.
At the age of about five or six, I discovered one of these gaps. Sticking my head inside, I saw little piles of grass (cuttings that had fallen off the lawnmower?), lots of twigs, and some vaguely cup-shaped leaves filled with rainwater.
My conclusion?
IT WAS A HOTEL FOR BIRDS.
It all seemed very simple. The leaf "cups" were for the birds to drink from. The twigs and grass were their "beds" (nests), but they'd got horribly messed up, which was why there weren't any birds staying there now.
I spent the next couple of months tidying up the "hotel", making neat little nests to lodge amongst the branches. When the birds still didn't come, I wasn't discouraged-- I figured they'd go to hotels when everyone else did, that is, in the school holidays!
A childhood belief about birds

others believed things like this
- When I was little, I thought that birds feathers were made out of twigs and cat hairs.— Lily
- Trees grew leaves as camouflage so birds would`nd nest in them. Don`t ask.— DaWind
- i used to beleve that when i grow up i'll be able to fly just like birds— tomba
- I used to think House Finches were baby birds and they'd later grow into Robins or something— Mica
- I used to believe that the school rabbit liked the red berries that grew in the hedge. But then he died.— Charlotte
- My dad told me that the reason Birds didn't get electrocuted on overhead wire was they had rubber feet!!— Derricki