This nest has been occupied for 5 years in the base of a Canadian Maple tree. II thought it had died out one winter, but bees were observed on a warm day flying out. There are 2 entrances, one at ground level, which is now closed up by debris.
I always feel joy when I see them flying, as they are in quite a public place. The bees have built a propolis curtain seen in second photo.
14 Sept 2021
Total reported by Ingo is 5