Monitoring alkali bee (Nomia melanderi) flight height with a vehicular bee sweeper in Washington State

Pollination by the alkali bee (Nomia melanderi) is essential for seed set in alfalfa seed production. N. melanderi is a solitary ground-nesting bee that aggregates in sub-irrigated salt flats. The Washington State Department of Transportation is proposing an upgrade of US Highway 12 that will pass through the Lowden-Touchet-Gardena seed growing district of southeastern Washington State. Speed limits are posted on county roads located near alkali bee beds and the proposed four-lane highway could pose a negative impact to the bees and seed yield in the area due to bee mortality from motor vehicular traffic. In order to mitigate the effects of traffic on N. melanderi, we established methods to assess alkali bee flight height and behavior. We constructed a ‘vehicular bee sweeper’ designed to capture insects at specific heights over county roads. This bee sweeper device involved sweep nets attached to a moving vehicle. In 2010, we determined the majority of N. melanderi flew at heights below 2.1 meters when no other factors (location, temperature, and wind speed) were considered. We found differences in bee abundance per location in 2010 and 2011. Environmental conditions such as temperature and wind speed had an effect on N. melanderi in 2010. Location, temperature and wind speed had an effect on bee flight height and behavior in both 2010 and 2011. By determining N. melanderi flight height and behavior, we can attempt to minimize the impacts of vehicular traffic from the new highway.