Sometimes bees are very hard to identify type. For example, the Africanized Killer Bees look just like a normal bee to the naked eye, which is why people in the areas those inhabit, are warned not to get too close because you can't tell which is which.
But I think you'll have to watch the yard a little longer to see what habit the bees develop for a closer ID. Some leave marks- we used to have carpenter bees, and those would bore small round holes on the underside of our wooden swing set. Some build nests in certain spots (house, bush, etc). Watch time of day too, that will help reduce variables.
If you have roses, be careful what you spray to control bugs on them- some of the insecticides will kill bees too even though it doesn't state that on the label. I would read up online first if you need to spray anything in the yard, to see if it's safe for bees.
