MOLT, MATURATION OF PLUMAGE AND AGING IN THE WANDERING ALBATROSS

We compare the pattern and rate of molt and plumage maturation in Wand ering Albatrosses (Diomedenea exulans chionoptera) using prebreeding a nd breeding birds from South Georgia (S. Atlantic Ocean) and Crozet Is lands (S. Indian Ocean). Immatures from both sites have a molt cycle w hich basically alternates moll of outer primaries in one year and inne r primaries in tile next year. This is similar to, but in its details more complex and flexible than, the molt of the smaller, sympatric Bla ck-browed and Gray-headed Albatrosses (D. melanophris and D. chrysosto ma). It differs from the wrap-around molt characteristic of Laysan and Black-footed Albatrosses (D. immmutabilis and D. nigripes). Juvenile Wandering Albatrosses have most new primaries when 5-year-olds but eve n at this age some birds have retained primary 1 since they fledged. M ales, but not females, from South Georgia replace more primaries than do Crozet birds. Adults breeding for tile first time molt fewer primar ies than birds breeding 7-11 months after a failed breeding attempt; t hese adults molt on average 6 primaries, similar to successful or fail ed Black-browed Albatrosses. Successful Wandering Albatrosses, in the 12 months before breeding again, only molt 7-8 primaries on average, i n contrast to the 11 primacies molted by biennial Gray-headed Albatros ses in their 16 month breeding interval. The duration of the interval between successive breeding attempts is probably the main constraint o n the amount of primary molt that can be accomplished. Failed, but not successful, Wandering Albatrosses breeding at Crozet molt more primar ies than similar birds at South Georgia. At both sites, the plumage of birds of both sexes gets whiter until about 20 years old. However, So uth Georgia males are already whiter than Crozet birds at 5 years old (presumably reflecting the faster molt rate of South Georgia birds) an d they maintain this difference for the next decade. In contrast, fema les from both sites mature at similar molt rates until age 10 years (m edian age of first breeding) when South Georgia birds become and stay whiter than Crozet birds. Plumage maturation rate is much slower in bi rds from Macquarie Island, but these may not belong to the same subspe cies, Conventional (Gibson) plumage scores do not provide a reliable m eans of estimating age of Wandering Albatrosses, except in very genera l (+/-3-5 year) categories, The pattern and extent of molt, however, c an age most immature birds of D. e. chionoptera to within one year; we provide a key for doing this.