Study population, nesting biology, and field collections
We sampled bees from an aggregation of M. tepidus timberlakeinesting along the shoreline of a coastal lagoon on the University of
California, Santa Barbara campus (34.410358 N, -119.850442 W). This
nesting aggregation hosts several hundred nests annually and has been
observed at this location since at least 2019. Nests are predominantly
concentrated along a 40 m stretch of the lagoon shoreline, within 2 m of
the water, and are found both in bare soil and beneath patches of Alkali
Heath (Frankenia salina (Molina) I.M. Johnst.). Nest initiation
began in mid-May 2023, and flight activity continued through July 2023.
We periodically measured soil moisture throughout the nesting site using
a TDR soil moisture meter (FieldScout TDR 300, Spectrum Technologies,
Inc., Aurora, IL) between June 2022 and May 2023 and found that the soil
was consistently at its saturation point (52% volumetric water
content).
We collected adult female M. tepidus timberlakei exiting their
nests between late June and early July 2023, by placing plastic cups
over nest entrances to capture bees departing on morning foraging trips.
We transported bees back to the lab within one hour of collection, where
they were weighed using a microbalance (0.001g precision). All bees were
paint-marked on the thorax using an oil-based paint pen to facilitate
identification during data collection and to prevent resampling on
subsequent days. After assays, bees were rehydrated and released at
their nesting site.