Rainbow Lorikeet (Trichoglossus haematodus) in a Black Bean tree (Castanospermum australe). Photo taken in the Royal Botanic Gardens in Sydney, Australia. The lorikeet is feeding on the nectar of the flowers.Image by Philip BouchardSuburban landscapes provide more consistent floral nectar than native bushland and support a greater abundance of large nectar-feeding birds

Why do parrots seem to do so well in Australian cities? One reason may be related to food (nectar) availability. Our research revealed that in most seasons, nectar was more readily available in streetscapes than in native forests, and that nectar-feeders tracked flowering. The constant food availability in streetscapes is likely to help explain why parrots are so successful in exploiting suburban environments.

To measure nectar availability in both suburban landscapes and native bushland, we first calculated the density of the main flowering plants in each environment. Then came the tricky bit- extracting nectar from the flowers using capillary tubes, and measuring the volume and sugar concentration using a refractometer.

Perhaps surprisingly, native forests and heathland generated similar amounts of nectar energy to suburban streetscapes in all seasons except spring, when the suburban habitat provided significantly more of this high-energy food resource.

The abundance of large nectar-feeding birds, including Rainbow Lorikeets, Musk Lorikeets, Red Wattlebirds and Little Wattlebirds were also recorded. We found that both Rainbow Lorikeets and Musk Lorikeets were present in higher densities within streetscapes than in the natural environment, indicating that large nectar-feeders certainly exploit the suburbs.

The number of birds in streetscapes also depended on the species that were flowering at the time, with numbers of both the Rainbow Lorikeet and Musk Lorikeets linked to eucalypt flowering, and Red Wattlebirds linked to the flowering of grevilleas and callistemons.

Suburban landscapes appear to provide a relatively constant supply of nectar, making an easy life for large-bodied nectarivores. This provides one explanation for the success of these avian icons of the suburbs.