Tiny Bees

 There are tiny black bees hovering over the greening grass on our front slope. What are they doing? There are no flowering plants there, just grass. They hover and move slowly back and forth like they are looking for something. Occasionally one will sink down to the ground for a few seconds, then power back up and resume scanning. 

I'd take a picture, but I don't have Josh's talent for insect pictures and I'm afraid they would just be little brownish black blurs. Anybody know what they are and what they are doing? I hope they aren't planning a large bee condominium complex in our front lawn. I want to do all I can to encourage native bees, but I'd rather not have a yard full of underground bees waiting to pour out and attack.