Annual emergence aggregations of ground nesting bees have been reported. Spring weather has generally been good for bees. Flight can be very heavy at nesting sites.
Male bees fly about the nesting area for mating purposes and the heavy flight causes concern.
They usually emerge before females. Remember, males emerge first, so if you plan to treat, be sure you have females building nests and activity is not just male territorial flight behavior. You should see new ground entrances with fresh sand turrets and females coming and going in the soil. Generally you need to spray the ground nest area twice with a soil-approved insecticide. Initially spray the area, then disrupt the surface with a rake or hoe, and then respray.