Bee hotels don’t “save” native bees: Disparate outcomes of nesting success among native and introduced cavity-nesting bee species

In an effort to conserve native bees, research and conservation programs have targeted increasing bee food resources or nesting resources. An increasingly popular idea among the public is the supplementation of cavity-nesting bee habitat with artificial hollow cavities inside nestboxes (often referred to as “bee hotels”). Such nestboxes provide educational opportunities for observing the nesting behaviors of many solitary bee and wasp species, but their value to their occupants requires further study.  We examined mason bee (genus Osmia) occupancy of nestboxes across 139 sites in Virginia during a 3-year study and recorded bee mortality from wasp parasitoids across a gradient in natural landcover.  The majority of nestboxes contained only nests of non-native Osmia species: O. cornifrons and O. taurus. When native Osmia were found in nestboxes, they were up to 23.8% more likely to experience wasp parasitism than introduced Osmia species. This difference varied with landscape, with native species especially vulnerable in sites with little natural landcover. This work extends the findings of a previous urban study on artificial nest structures to more insect fauna and across greater landcover diversity. We suggest that the benefits of adding artificial nesting structures may be conferred primarily to non-native species (another driver of native bee declines) rather than to native species. Although bee hotels offer unique educational awareness opportunities for human observation of cavity-nesting bee behavior, the use of bee hotels in anthropogenically disturbed areas primarily promotes introduced mason bee species proliferation and should not be endorsed as a conservation measure.