Recent work at several central South Island sites has shown that the bird-pollinated mistletoe Peraxilla tetrapetala (Loranthaceae) is extensively pollen-limited. We studied the diet, time-budget, and densities of its principal pollinator, bellbirds (Anthornis melanura, Meliphagidae), at Craigieburn to find out what aspect of bellbird ecology may be limiting pollination.
Honeydew is produced by a scale insect (Ultracoelostoma assimile, Margarodidae) in some Nothofagus forests of South Island, New Zealand. The quantity of honeydew present and its sugar concentration varies through the year. Honeydew is a valuable resource for bellbirds (Anthornis melanura), tuis (Prosthemadera novaesealandiae) and silvereyes (Zosterops lateralis). Bellbirds and tuis were commoner in forests with more honeydew. Bell- birds spent more time feeding on honeydew when its sugar concentration was low.
Worldwide declines in bird numbers have recently renewed interest in how well bird–plant mutualisms are functioning. In New Zealand, it has been argued that bird pollination was relatively unimportant and bird pollination failure was unlikely to threaten any New Zealand plants, whereas dispersal mutualisms were widespread and in some cases potentially at risk because of reliance on a single large frugivore, the kereru (Hemiphaga novaeseelandiae). Work since 1989, however, has changed that assessment.