Understanding foraging and nesting behaviour of ground nesting bees in Dunedin, New Zealand

Solitary bees (Hymenoptera: Insecta) are key pollinators for natural ecosystems and agricultural crops. Unlike social bees, such as bumblebees and honeybees, solitary bees forage and build their nests independently and are more vulnerable to ongoing threats, including habitat loss and pesticides, than social bees. New Zealand has 27 native solitary bee species, and understanding foraging and nesting behaviours of native bees is critical for conservation efforts. However, few New Zealand studies have investigated the behavioural ecology of native bees. We looked at three native bee species in Dunedin: Lasioglossum sordidum (Halictidae), Nesocolletes fulvescens (syn. Leioproctus fulvescens), and Nesocolletes pekanui (syn. Leioproctus pekanui) (both Colletidae). These three native bee species were found at four urban nesting sites. Diurnal female nesting and foraging behaviours were observed and recorded regularly over a single summer. Both L. sordidum and N. fulvescens foraged more frequently and for longer periods in the morning than during midday and afternoon periods. Activity peaked when temperatures were between 20°C and 25°C at all four nesting sites. Wind speed significantly decreased general activity whereas ambient temperature significantly increased activity at one site. Additionally, both environmental factors influenced the number of nest entries and foraging trips of L. sordidum. Foraging trips of N. pekanui could last more than one hour, compared to L. sordidum and N. fulvescens, which foraged for c. 24 minutes on average before returning to the nest. In contrast, all three species spent similar lengths of time in the nest throughout the day. These findings contribute to an understanding of New Zealand native bees, but more research is needed to aid future conservation efforts.