Possums were initially introduced to New Zealand from Australia between 1837 and 1840 to provide a fur industry. Later releases ensured that they spread throughout New Zealand. Today, the total population is thought to number over 70 million. Each night these millions of possums eat tonnes of native vegetation, competing with birds like kerer? for important foods, especially flower buds, flowers, and immature fruit. As a result, where a high density of possums occurs, few nutritious foods, such as flowers and ripe fruit, remain to support kerer? breeding. While not thought to be an active hunter of birds, when a possum encounters a bird's nest it will often flush the adult off the nest and eat the egg or chick, including those of kerer?.

Stoats were brought to New Zealand between 1884 and 1889 by the government to control rabbits. Stoats are notoriously ferocious hunters, and readily climb to the tops of tall trees. They soon spread through all forests, preying on native invertebrates, lizards, bats and birds, including kerer? eggs, chicks and adults. Stoats are a major contributor to the silence of New Zealand mainland forests.  Some idea of just how full iof birdsong our forests orgignally were can be gained from visiting island sanctuaries such as Kapiti, Ulva and Tiritiri Matangi and increasingly, mainland islands such as Karori Wildlife Sanctuary.

Cats were brought to New Zealand as companions of the first Päkehä settlers. They soon became feral and bred in the wild, preying on chicks and adult kerer?. Pet cats also pose a threat to native wildlife in rural and urban areas. Cats are able to forage by day and night. Ideally, people living within a kilometre of a native forest reserve where management is underway to promote native wildlife populations should not have pet cats. Those people with cats should consider keeping their pets indoors at night to reduce their impact on bird populations.