Seeds from many native trees rely on kererū for dispersal. With the extinction the huia and moa, kererū are the only native birds with a wide enough mouth to swallow large fruit. These include fruit of karaka, pūriri, taraire and tawa. The North Island kokako can also consume these fruit but their natural distribution does not reach south to the Wellington area.
In some bush areas of New Zealand where kererū have declined, scientists have found that the regeneration of some native tree species fell up to 84% in two years. This is not the case in the Tawa reserves, where kererū numbers have increased markedly. For Redwood Bush, this is evident in the following graph, but is also applicable to other bird species. The recent increase is the result of effective pest control, and the resurgence of native tree growth, with more seeds and fruit available from trees such as tawa. and pigeonwood (porokaiwhiri)
Source: Roper G, 2022. Redwood Bush, Tawa. Friends of Tawa Bush Reserves.
Images credit Paul Bouda
Source Article Gil Roper: FOTBR February 2023 Newsletter