[BEES4U]

There are two kinds of Mason bees that are available.
The Blue orchard Bee, BOBs and one adapted to Calif.
I tried both of them and had one bee emerge form 50 tubes that were ocer wintered in my fridge at 40 degrees F.
Some people make mud available at the nesting site.
Good Luck,
Zip Code 93010
Ernie

 

[BEES4U]

Here's one source:
Unfortunately, they are out of stock.
http://www.knoxcellars.com/Merchant..._Code=KCNP&Product_Code=OCBT&Category_Code=BO

You might consider putting out some tubes to see if your local ones might use them this season.

Supplier list:
http://www.pollinatorparadise.com/solitary_bees/supply.htm

Ernie