Bees (Hymenoptera) are key insect pollinators for natural ecosystems and agricultural crops. While social bees, like honeybees and bumblebees, are important pollinators, there are ~20,000 species of bees worldwide, and ~ 85% of them are classified as solitary. Unlike social bees, individual solitary bees build their nests and forage for food independently. New Zealand has 28 native solitary bee species. While they have small population densities, they contribute to pollinating native plants and agricultural crops. Furthermore, solitary bees are more vulnerable to ongoing threats, such as habitat loss and pesticides, than social bees. However, there is little knowledge about their behavioural ecology in New Zealand compared to other international solitary bee species. Foraging and nesting behaviour are critical for the survival of native solitary bees. Understanding more about their behaviours will help fill the knowledge gaps of their biology.

The first study (Chapter Two) aimed to observe the foraging and nesting behaviour of three native bees species at their nesting sites within Dunedin, New Zealand: Lasioglossum sordidum (Halictidae), Nesocolletes fulvescens (previously known as Leioproctus fulvescens) and Nesocolletes pekanui (previously known as Leioproctus pekanui; both from Colletidae). These three native bee species were found at four urban nesting sites. Female nesting and foraging behaviours were observed and recorded periodically throughout the day using Go Pro cameras. Both L. sordidum and N. fulvescens foraged more frequently and for longer periods in the morning than in midday and afternoon periods. Nesocolletes pekanui was observed foraging for more than one hour, compared to L. sordidum for 24.47 minutes and N. fulvescens for 24.74 minutes on average. Currently, there are no explanations for the foraging behaviour for Nesocolletes pekanui. On the other hand, all three native solitary bee species had similar nesting periods throughout the day. Furthermore, I investigated how ambient temperature and wind speed affected activity of native solitary bees. Activity peaked between 20°C and 25°C at all four nesting sites. Wind speed significantly decreased the general native bee activity, while ambient temperature significantly increased native bee activity only in Botanic Gardens A. Additionally, both environmental factors affected number of nesting entries and foraging trips of L. sordidum only compared to other two native bee species, where factors don’t significantly affect their behaviours throughout the day.  

The second study (Chapter Three) investigated the floral specialisation of the three native solitary bees. Understanding their floral specialisation might help us to predict how habitat loss and fragmentation can affect the native bee communities. Floral surveys and pollen collections were conducted during the month of Janurary, 2023. At that time of the summer season, Nesocolletes fulvescens specialised only on Asteraceae pollen. While L. sordidum and N. pekanui foraged on multiple floral species, they predominately collected one pollen type. Lasioglossum sordidum mostly collected pollen identified as Ranunculaceae, while N. pekanui foraged for Veronica pollen.

Observations of nesting and foraging behaviour and quantifying floral preferences are important as it highlights how behavioural patterns change throughout the day and their exploitation of available floral resources in urban habitats. This study advances our understanding of native solitary bees' behavioural ecology and assists future conservation efforts.