Enchanted Mesa had the first nests of the season, made by Osmia lignaria, recorded on May 29, 2014. This is rather late for the Boulder area, but it was a late spring.
North Teller Lake had the most nests made in a single block, with a whopping 44 completed nests. Since some nesting tunnels were used more than once, it is possible to get more nests (44) than there were tunnels (40).
Settler’s Park had the least nests, with a mere 6 completed nests. This is probably because the block was placed in a shady location and became overrun with earwigs and spiders. Still one nest plugged with whole leaf pieces and five nests plugged with loose debris were completed during the fall months.
Chapman Drive had the most diversity, with 7 different types of nest plugs including mud, loose debris, resin, resin with debris, chewed vegetation, whole leaf pieces, and silk.
Lefthand had the least diversity, with only one species, the alfalfa leaf-cutting bee, Megachile rotundata. Despite only one species nesting, there were 21 nests in the bee block.
Crown Rock had the latest nesting activity with a female Dianthidium still working on a nest on October 24, 2014. Apparently the rocks hold the heat as there were still flowers blooming too. Microclimate is so important to these tiny critters.
Next time you are at a City of Boulder Open Space and Mountain Parks trailhead, look around for a bee block. You might just find one.