Black-billed gull  (Larus bulleri)

Despite a substantial decline on South Island over the past ten to twenty years, the black-billed gull remains more common on South Island than North Island, where it has actually expanded its range since the 1970s. It is hoped that its overall declining trend has reversed recently, partly due to a change in agricultural practices that has seen more insects and worms being revealed by ploughing. The black-billed gull has developed a habit of following ploughs and aiding farmers by picking out insect pests. However, the breeding habitat of the bird continues to decline in size. This reduction in habitat is the cause of the drop in gull numbers over the last 30 years as land is increasingly turned over to agriculture. Additionally, breeding habitat is currently threatened by the spread of exotic lupins which clog the waterways (2) (5).

The New Zealand Government has launched the New Zealand Biodiversity Strategy to respond to its obligations under the Convention on Biological Diversity. This includes management of wetland habitats by protecting them from development, as well as by planting appropriate plant species in areas recovering from disturbance in order to stabilise the soil and reduce fertiliser run-off that can encourage the growth of exotic species, such as lupins, at the expense of native species. The water level must be maintained and a water care code has been established to ensure that users of wetland habitats are able to act responsibly (6).