Establishment of a Native Cavity-Nesting Bee (Exoneura robusta) After Translocation Into an Urban Environment

Urban environments are increasingly considered as potential sites for pollinator conservation, yet quantitative evaluations of insect translocations into cities remain limited. We report the outcome of a small-scale translocation of the native cavity-nesting bee Exoneura robusta from forest habitat into an urban campus in Melbourne, Australia. Adult bees from natural nests were relocated into artificial balsa-wood nests and installed across shaded and open microhabitats within an urban greenspace. Nest-level success was defined as the presence of brood in the first summer following translocation and the presence of adults the following winter, indicating completion of a full annual cycle. We hypothesized that the native cavity-nesting bee Exoneura robusta can successfully establish in urban environments following translocation, and that nest success is associated with initial adult group size, canopy cover, or local floral richness. Of the eleven artificial nests established, six met this criterion for success. We used binomial generalized linear models to test whether initial adult group size, canopy cover, or local floral richness were associated with nest success. None of the measured variables showed strong support relative to a null model, suggesting that simple nest-level predictors did not explain variation in establishment outcomes within this small experimental dataset. Successful nests occurred across a range of urban microhabitats, including open sites adjacent to built infrastructure and locations beneath dense canopy. Our findings demonstrate that E. robusta can persist for at least one annual cycle following translocation into an urban environment. Although limited in scale, this study provides initial evidence that native cavity-nesting bees can establish within compact urban greenspaces and highlights the need for larger experiments incorporating finer-scale biotic and microclimatic measurements.