Regional patterns of nectar availability in subtropical eastern Australia

Context: There are few detailed data for short-term (≤ monthly) fluctuations in flowering and nectar availability at relatively large spatial scales. Such information is critical for understanding the governors of variation in flowering and for the management of floral resources assisting the persistence of nectar consumers in landscapes. Objectives: To obtain monthly measurements of patterns of nectar availability in a 314,400 ha region, and to relate these patterns to potential environmental predictors. Methods: Flowering was measured at 83 sites in natural vegetation and in eight domestic gardens in subtropical, eastern Australia. A nectar-availability index was developed was based on nectarivore visitation rates and plant-specific flowering patterns. Spatial–temporal patterns were related to environmental variables using boosted regression trees. Results: The large between-year variation was due mostly to irregular flowering by several eucalypt species. There was a ‘lean season’ in the austral spring (August–September). Coastal vegetation was an important source of nectar for much of the year, including the lean season. Gardens produced prolific nectar throughout the year, peaking in August–October. Conclusions: Nectar availability was most closely associated with primary productivity over the previous 12 months, average annual solar radiation, topographic wetness, and rainfall over the previous 6 months, although some relationships seemed counter-intuitive. There were large differences in nectar availabilities among broad vegetation types (especially rainforests vs. sclerophyllous forests), which partially accounted for the unintuitive results.