I found what appeared to be a colony of what looked like small bumble bees. They seemed to be uing the same small hill of clayish soil for what looked like individual nests/holes. There were about a dozen or more flying in and out of the individual holes while it looked like others were buzy burrowing. I will try and post a photo of nest.

What species of bee are they?

Again, they looked like small bumble bees but only about one third the size