Bee droppings

Matt B. writes.

"We're seeing a curious phenomenon this year, and hope you can enlighten us.  As we've done previous years, we set our cocoons out in plastic tubs with little holes cut in to let the bees emerge.  This year the bees (or perhaps some other creatures we haven't seen) seem to be leaving splats of mud on the outside of the release tubs, concentrated around the holes.  I've attached a photo of one of the tubs.  You can see they've dropped some mud on the plywood on their approach to the tub as well.  We're seeing male bees flying, but haven't seen any female bees or any activity around the nesting tunnels.  Have you seen this before?  Are the bees doing it?  Do you know why?"  

 These 'splats' of mud are the 'post emergence fecal droppings' or simply put 'bee poop'.  It  is a good sign to tell us that bees have emerged.   Now that warmer spring temperatures have arrived on the West coast of North America female mason bees will soon be emerging, mating and pollinating.  Thanks for the photo and your questions!  Margriet