My wifes sister discovered these bees flying in and out of an iron bridge structure about a year ago. These recently taken pictures show they are still going strong. The bees have quite a lot of hair on them which is apparently common on native black bees when coming out of winter. I can't imagine the location they have chose for their nest is as well insulated as a tree cavity, so they probably needed them. Needless to say it demonstrates how bees can adapt to their surroundings.