Changes in bird abundance following Common Myna control on aNew Zealand island

Abstract

We censused land bird populations on a small island during a year of intense trapping of the Common Myna Acridotheres tristis. We successfully removed mynas on Moturoa Island, Bay of Islands, with populations on the island decreasing In most areas, while holding steady on other, nearby islands where no trapping was conducted. The populations of many other bird species increased coincidently with the removal of mynas. This was most notable in the Tui Prosthemadera novaeseelandiae, Grey Warbler Gerygone igata, and Blackbird Turdus merula. Of 60 species-route comparisons, we found that 23 (38%) increased, 33 (55%) had no change, and only four (7%) decreased. The relative role of rats Rattus spp. and succession is also discussed. Tile historical decline of many species in the North Island of New Zealand may have been related to the concomitant increase of tile myna, and control of this species may be warranted in some cases, especially where restoration of the native fauna is the objective.