Weird Bee Question

[goatmanbees]

I was called to do a removal today and found weird bees. That looked and were the same size as honey bees. They were all black, carried pollen on the under side of the abdomen and were carrying in bits of leaves into to hive. 
Any ideas what it is?

[JWChesnut]

You are describing a leaf cutter bee
 Megachile rotundata
http://www.fritzhaeg.com/garden/initiatives/animalestates/animals/leaf-cutter-bee.html

Leaf cutter bees are in huge demand for alfalfa pollination.  North West alfalfa seed farmers pay big dollars for Bee Boards-- Planks drilled to support communities of leaf cutters.  Honey Bees do a poor/non-existent job on alfalfa pollination.

Leaf cutters will colonize the straw/bamboo arrays used for mason bees.

[goatmanbees]

Eureka!!! Thank you!!