caique keeps flying into windows

Even though the windows are closed, my budgie keeps trying to fly into them during out-of-cage time. I'm worried they'll hurt themselves. How do you handle this? Window stickers? Keep curtains closed?

Okay but counterpoint — what about birds that are the complete opposite? My cockatiel breaks every rule lol.

Second vote for BST. They boarded my Eclectus last summer and I could tell Lucky was well cared for when I picked them up. Total peace of mind.