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The Chatham Islands tomtit (Petroica macrocephala chathamensis) is a small forest passerine with a threat ranking of nationally endangered. It is restricted to 2 islands of the Chathams group that are free of introduced predators (Rangatira and Mangere Islands), and 1 with mice (Mus musculus) and feral cats (Felis catus) (Pitt Island). We carried out a translocation of 35 juvenile tomtits from Rangatira (10 male, 10 female) and Pitt Islands (6 male, 9 female) to Awatotara Valley, Chatham Island in January 2011. Mean weight at capture of Pitt Island tomtits was lighter than that of the Rangatira Island tomtits. Tomtits were held captive in aviaries for 1-3 days on the source islands and 2-4 days at the release site. Weight loss of tomtits in captivity prior to transfer averaged 1.8% of body mass per day held and was more pronounced in birds sourced from Rangatira than Pitt Island. Two birds died during the first night after transfer, but the other 33 were released in apparently good health. Eighteen of the released birds were seen at least once, and 11 regularly until 28 March (at least 55 days after release). During the following 12 days, all 11 of these tomtits disappeared. We discuss possible reasons for their disappearance, and aspects of the translocation that may be useful for future translocations of tomtits and other species with a similar ecology.