Which small bird is New Zealand's smallest endemic bird?

New Zealand’s smallest endemic bird is the rifleman.

Known scientifically as Acanthisitta chloris, the rifleman is a tiny insect-eating passerine found in forests on New Zealand’s North and South Islands. Fully grown birds measure about 7–9 centimetres long; males usually weigh around 6 grams and females about 7 grams.

Despite its wren-like appearance, the rifleman is not a true wren. It belongs to Acanthisittidae, the New Zealand wren family, of which only two species survive. The bird’s name comes from the plumage’s resemblance to the uniform of a colonial New Zealand rifle regiment.

The rifleman was first described in 1787 by Anders Sparrman, who initially placed it in the nuthatch genus Sitta. It feeds by spiralling up tree trunks in search of insects and maggots. Forest fragmentation has isolated populations, although the species remains widespread compared with other New Zealand endemics.