Impact on birds
The behaviour of three native bird species (tui, bellbird, kaka) is known to be affected by wasps removing honeydew.
Elliott et al. (2010) recently showed that several common and widespread bird species have had significant declines in their abundance of the last 30 years; attributable to the impacts of a number of introduced species, but especially wasps.
Tui spend over 80% of their foraging time on honeydew but reduce their feeding on honeydew or leave beech forest when honeydew falls below a threshold level (2500 J m-2).
Bellbirds remain in the forest on days when the standing crop of honeydew was low, but reduce their time spent feeding and on activities like singing, flying, social interactions and grooming.
The behaviour of kaka also changes when it became unprofitable for them to forage on honeydew.
The devastating effects of introduced wasps in New Zealand, particularly on kaka (the forest parrot, here beautifully filmed) remain a serious issue. The horde of yellow and black marauders has left scientists struggling to protect animal and human victims. The ultimately sad film looks at the effect on the ecosystem of wasps, who compete with natives for honeydew and prey upon insects.