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Breeding success of 5 Cory’s shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several subcolonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Cory’s shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was significantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding success recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year following eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several ecological advantages on more ecosystem components than Cory’s shearwater alone. Improved eradication tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.

Six archaeological sites up to 1000years old on Aitutaki, Cook Islands, have yielded bones of 15speciesof birds, five of which no longer occur ontheisland: Pterodromarostrata(Tahiti Petrel);Sula sula(Red-footedBooby); Dendrocygna,undescribedsp.(alarge,extinctwhistlingduck); Porzanatabuensis (Sooty Crake); and Vini kuhlii (Rimatara Lorikeet). Of these, only S. sula and P. tabuensis survive anywhere in the CookIslands today.The nearest record of anyspecies ofDendrocygnaisinFiji.Asidefrom theaquaticspeciesEgrettasacra (Pacific Reef-Heron) and Anas superciliosa (Gray Duck), the only native, resident land bird on Aitutakitoday isthe SocietyIslands Lorikeet(Viniperuviana), which may have been introduced from Tahiti. Residents ofAitutaki note that Ducula pacifica (Pacific Pigeon) and Ptilinopus rarotongensis (Cook Islands Fruit-Dove)also occurredthere until the 1940sor 1950s.There isno indigenous forest on Aitutaki today. The bones from Aitutaki also include the island's first record of the fruit batPteropus tonganus. Limestone caveson the island of Atiu yieldedthe undated bones of sixspeciesof birds, three of which no longer exist there or anywhere elsein the Cook Islands: Gallicolumba erythroptera (Society Islands Ground-Dove),Ducula aurorae (SocietyIslands Pigeon),and Vinikuhlii. Each of these specieshas been recovered from prehistoric sites on Mangaia as well. The limestone terrain of Atiu is mostly covered with native forest that supports populations of Ducula pacifica, Ptilinopus rarotongensis, Collocalia sawtelli(Atiu Swiftlet), and Halcyon tuta (Chattering Kingfisher). The survival of these land birds depends upon protection of Atiu's forests.