Population status, breeding biology and conservation of the Tristan Albatross Diomedea [exulans] dabbenena

摘要

Tristan Albatross Diomedea [exulans] dabbenena is the most genetically distinct of the five taxa that form the Wandering Albatross superspecies, and has been listed as Endangered. It breeds only on Gough and Inaccessible Islands in the Tristan da Cunha group, central South Atlantic Ocean. The entire breeding population was surveyed during 1999-2000. A mid-September survey at Gough Island recorded 1, 129 chicks, equivalent to an annual breeding effort by approximately 1,500 pairs. Only one chick was present at Inaccessible Island in 1999, and another pair laid an egg in 2000. The annual breeding effort at this island has not exceeded three pairs since the 1950s. None were found during an incomplete survey at Tristan, where the species bred in the past, but birds were seen flying over the island. A complete survey and attempts to promote recolonization of Tristan are warranted. Breeding success at Gough Island averaged 63%, and no birds that bred successfully attempted to breed the following year. Breeding success was greater and less variable in a large colony at Gonydale than at a peripheral colony at Tafelkop. Young birds returned to the island after 3-4 years (4-5 years old), and the modal age of first breeding was 8 years, with some individuals breeding as young as 6 years. Most chicks (81%) recruited to their natal colony, but some recruited to colonies up to 3 km from their natal site. Among adults, fidelity to partners and breeding colony was high. Of nine birds recovered away from the island, at least four were killed by longline fishing. despite its known mortality on longlines, the Gough Island census exceeded demipopulation estimates from the 1970s and early 1980s, possibly due to incomplete coverage by previous surveys and a poor breeding season in 1998. Given the lack of evidence for a population decrease, Tristan Albatross should be listed as Vulnerable. It is the third rarest albatross species, however, and its population size warrants monitoring. We provide guidelines for repeatable censuses at Gough Island.