Watching Bees for Conservation

Our prairies host myriad pollinator species, from bees of all sizes to flies, wasps, and beetles. The plant-pollinator team has spent a large part of this season surveying prairie pollinator diversity, both within the south Sound and further afield. There are several reasons for these surveys. First, we are continuing to collect data as part of a larger study examining how restoration affects plant-pollinator networks and conservation of Taylor’s checkerspot host plants. At the same time, we are collecting baseline data on pollinator composition and diversity, since there is little known about the pollinating fauna of the PNW prairies. Finally, our surveys are intended to detect if rare or declining pollinator species inhabit our prairie ecosystems.

A bee feeding on nectar from a large blue-eyed mary (Collinsia grandiflora) flower.

In the space of just two seasons, we’ve seen strong differences in our pollinator communities—perhaps because of weather differences from year to year.  Last year, for example, we saw fewer bees than we expected, especially bumble bees, and also less flower flies—the bright yellow and black bee mimics that also pollinate many of our flowers—were abundant. Although we don’t know for sure why that was, we suspect the cool rainy weather during the early part of the season made it difficult for early season bees to forage. By contrast, this year, we’ve been seeing highly abundant bees and less abundant flies at most sites.

A bee perched on a cut-leaf microseris (Microseris lanciniata) flower.

The abundance of bees this year means that we’re seeing some interesting diversity! We have at least 5 species of bumble bees (Bombus) in south Sound prairies: the yellow-faced bumble bee, the California bumble bee, the fuzzy-horned bumble bee, the yellow-headed bumble bee, and the black-tailed bumble bee. We see hundreds of tiny black sweat bees (Hemihalictus), small-to-medium sized striped bees (both sweat bees and miner bees), long-horned bees, beautiful metallic blue leafcutter bees (Osmia), and of course the stunning shiny green bees (mostly Agapostemon). Many of them are generalist foragers, meaning they will visit a wide variety of flowers, but a few are more specialized, like the bee we see on death camas. Sometimes we see fascinating behaviors, such as the leafcutter bees at Cavness and Wolf Haven that cut out round patches of pink Clarkia flower petals and carry the petals away to line their nests. Why Clarkia?  Who knows…but having a nest lined with gorgeous fresh pink flower petals can’t be all bad. 

A bee on a snowberry (Symphoricarpos albus) plant.