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We used a long-term replicated before-after control-impact (BACI) sampling design to monitor the effect of aerial 1080 possum-control operations on common forest bird populations. Paired treatment and non-treatment sites in the Rolleston Range (East Coast, South Island) and Alexander Range (West Coast, South Island) were monitored once before 1080 treatment during winter 2012 and for three successive summers afterwards. Mammals (possums Trichosurus vulpecula, rats Rattus spp. and mice Mus musculus) were monitored with chew cards, and forest birds with five-minute counts. Possums decreased to negligible levels in treatment sites, but increased over time in non-treatment sites. Rats were only present at the West Coast sites, where there was a significant, but short-lived, decrease post-1080. Mouse abundance showed almost no effects post-1080, but increased at the East Coast sites after a beech …