Over the weekend I built a pair of nesting blocks for native bees. Many species of native bees (such as leafcutter bees, mason bees, and small carpenter bees) are solitary cavity nesters. Individual female bees will seek out abandoned beetle tunnels in wood, hollow plant stems, and other cavities in which to deposit their eggs. It is easy to help these species by providing nesting sites in the garden. Our home garden has a nest site that has been used for several years and I have recently begun placing nesting sites in school gardens.
Nesting blocks for bees can be incredibly simple. The ones that I constructed over the weekend consist of a block of untreated lumber with holes drilled in it, a backboard for attacking to a post or other structure, and an overhanging roof. The blocks of wood that I used are more than six inchhes deep - many species of bees will not nest in short tunnels.
I'm not sure where these nest blocks will go as of yet, but I plan to build several more before spring. With luck, next winter the drilled holes will be filled with overwintering bee larvae and pupae. The picture below shows several leafcutter bee larvae in a bamboo stem that I recently pulled from from the nest site in our garden.
Next up on my woodworking projects list is nesting box for bumble bees.