My WFH home office is on the second floor outside the window is a cedar, hemlock and yew next to each other and intermingled. The window faces the south side of the trees. This time of year large bees, larger than honey bees but are svelte if they are bumblebees, hover a foot or two off the trees but zoom away only to return within a few seconds. They do this when the day is at its warmest. What's going on? They don't land and it seems like they're using energy for no obvious return.