Recommend Nesting Blocks for Mason Bees
We've got foraging down, maybe move into nesting. For people who would like to go above and beyond, ask if they'd take a fence post and drill holes in it for the assorted bees they'd be attracting to their yard. They're easy to build, but for those non Do It Yourself-ers they are sold online (just google Mason Bee Nesting Block, or Orchard Mason Bees.) At the very least it would be good for the data to ask people if they have nesting blocks setup and if the bees are active during the time of year that the sunflowers are blooming.
How to Build a Nesting Block.
It's very simple, I've had people do this and have great success. Though I'd say they have more success the closer they live to a forest. If you're not near a forest or aren't having luck with your nesting block it might be beneficial to drive to a forest and leave it there in a tree for a weekend. Mason bees are sold online but you usually need to pre-order them.
Take a fence post or solid piece of wood, (something that would be used for a support) and drill holes in it. Just go down the line of drill bits you own and devote a row to each size. Label what size was used for each hole. Holes need to be 3 to 5 inches deep into the wood, (the larger the bit the deeper the hole). Try to keep the holes clean, meaning try to get as much stuff out of the holes as you can. Using sharp drill bits can help. DON'T DRILL ALL THE WAY THROUGH THE WOOD! They don't nest in tubes with two entrances!
The drill bits don't need to be very large. I may be wrong but 1/4th is about medium or small, and 3/8's is pretty large. I don't know of much else that nests in anything larger (though I might be wrong).
It is optional to add another piece of wood to act as a 1 or 2 inch over hang. But not needed.
It's also optional to line each hole with paper or straws for easy cleaning after the bees have nested in them.
Someone I know in Illinois did this and over the summer months attracted a Leaf Cutter bee that actually used the flower petals to sunflowers for their nest.