Cavity nesting by Stitchbirds (Notiomystis cincta) was studied on Little Barrier Island by adding artificial nest sites (boxes) in a breeding habitat. The addition of boxes was a test of the theory that the number of breeding pairs of cavity nesting species is limited by the availability of suitable holes for nest sites. Site limitation is also said to prevent males of these species from taking more than one mate. This theory was tested by placing some boxes close to natural nest sites and other boxes. Results showed that the number of breeding Stitchbirds was not necessarily limited by the availability of sites, and that lack of sites did not restrict male birds to monogamy. The boxes could be a useful management tool for enhancing this rare species.