When the Howlibird pulls the peg out of the ground, which supports the small wooden logs, it's still nighttime outside. Then when the howlibird flies into the sky and chases the Smurfs again, it's daylight all of a sudden. Then when the Smurfs hide in the hollow log, it's nighttime again. Then when they run through the woods, it's light out again, then there's a night sky when Brainy jumps onto a tree, then daylight again when the Smurfs return to the village.