This is a song that we sing at our preschool but I believe it was sung by the children’s musician: Tim Cain. We have all children in a large circle holding hands up high as the open windows and it starts with one child being the bird going in and out of the open windows, while the rest of the children sing:

“Bluebird, bluebird, through my window,
Bluebird, bluebird, through my window,
Bluebird, bluebird, through my window,
Oh…you make me so ha-appy…it’s hugging time”

And the one bluebird picks a child
(who hasn’t had a turn yet),
hugs him or her, then the song is repeated until all children have been hugged (or gently tapped) and have gotten a chance to be bluebirds going in and out of the open windows. Works well with several adults (depending on the size of the group), to remind which kids haven’t been chosen yet, (otherwise they pick only their best friends over and over).