Dune Silver Bee

A question of synchrony: phenological cuing in the dune silver bee and one of its important floral resource, the silky beach pea

Rachael Olliff
Humboldt State University

The dune silver bee (Habropoda miserabilis) is a native solitary bee that is thought to be one of the most important pollinators on the coastal dunes of Humboldt Bay. Its flight season occurs between March to early June. During this time, the bees emerge and mate, and the females lay eggs in underground nests excavated in the sand. Ideally, the timing, or phenology, of the dune silver bee’s flight season will match that of its preferred nectar plants. However, the phenology of pollinators and the plants they visit has become an important conservation concern in the light of climate change. As changes in climate take place, there is potential for phenological mismatches to occur between plants and their pollinators. Climate change will have the greatest effect if the abiotic cues used by pollinators to emerge from their nests are different than the ones used by plants to initiate blooming. Therefore, it is critical to understand what is cuing the flight phenology of our native bee species, as well as their floral resources, in order to implement successful management practices to conserve these species.

With support from a conservation grant from Sequoia Park Zoo, Rachael Olliff is conducting a field study to characterize the flight season phenology of the dune silver bee and the blooming phenology of its main floral resource, the silky beach pea (Lathyrus littoralis). Rachael will monitor five sites on the North Spit of Humboldt Bay, recording the dates for silver bee emergence and nest excavation, and counting the numbers of open beach pea inflorescences every five days. She will then analyze the data to determine if phenology of the dune silver bee or the silky beach pea is correlated with potential abiotic cues such as soil temperature, soil moisture, precipitation, air temperature, or day length.

To raise awareness about bee conservation on the dunes, Rachael will also create a manual with information about silver bees, citizen science methods to track phenology of silver bees and their nectar plants, and conservation actions that can be taken to support bees on the dunes. This manual will be made available through the Humboldt Nature Center. Results of her study will be submitted to the Fish and Wildlife Service and the Bureau of Land Management, providing these agencies with information that will help inform habitat conservation and management actions in dune areas where this important native bee species occurs.


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