I do not close my hive up, it is always open. The entrance excluder is always attached but is always 'up'. The bees I'm talking about I've seen just after dark, but also very early in the morning and the middle of the night. They are on the landing board with access to the hive, they just happen to all hang around the left hand side and wander around apparently aimlessly. I guess they could be guard bees but thought they would be more spread out if this was the case.
Interesting, whatever the case may be!
Bees need sun light to navigate. If they do not make it back to the hive before sundown, they find a place to land and then return in the morning. If you close your hive up after dark during the summer, come sun up you will start seeing the bees return and bunch up outside of the hive.