Hello! I am really glad you asked, as the windows must ALWAYS be shut when not in use. Bees do not want light inside of their beehives for extended periods of time. If you were to accidentally leave it open for the short term (a few hours or a day or two) the bees may become agitated, but extended long periods (multiple days or weeks) might force the bees to abscond entirely. Using them for simple observation and inspection causes not much change in the hive. I hope this helps!