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Acanthisittidae is the New Zealand wren family, a major branch of Passeriformes distinct from both Tyranni and the songbirds of Passeri. The rifleman is one representative. The familiar word “wren” is not by itself evidence that these birds belong with every other small bird given that common name.^[ref]

The rifleman searches trunks and branches for small invertebrates and makes short flights between feeding sites. Such observations describe how a living member uses its environment; they are a different kind of evidence from the DNA comparisons used to establish the family's evolutionary position.^[ref]

A useful classification test therefore asks two separate questions: does another bird share a similar body shape or feeding habit, and does it share the ancestry indicated by a phylogenetic tree? Similar ecological demands can produce similar appearances in different branches. Broad genomic sampling places Acanthisittidae in the passerine tree without defining the group merely by small size, a short tail or an English common name.

The rifleman, Acanthisitta chloris, is a small New Zealand forest bird in Acanthisittidae. It has short wings, a very short tail and a slender, slightly upturned bill. Males and females differ in plumage: males have green upperparts, while females are more brown and speckled, an example of sexual dimorphism.^[ref]

Its way of feeding is closely tied to the forest's surfaces. A rifleman searches tree trunks, bark and foliage for small invertebrates and usually moves between feeding sites by short flights. Watching whether a bird probes beneath bark, picks prey from a leaf or catches it in the air distinguishes different foraging actions rather than treating all insect eating as the same behavior.^[ref]

The species also illustrates cooperative breeding. Related young can help feed a later brood alongside the breeding pair. To describe this correctly, an observer must identify individuals and record who delivers food: counting visits to a nest alone cannot distinguish parental care from help supplied by other group members. Such observations connect the family group to the survival of young without assuming that every bird at a nest is a parent.^[ref]