INDIVIDUAL QUALITY AND REPRODUCTIVE-PERFORMANCE IN THE GREY-HEADED ALBATROSS DIOMEDEA-CHRYSOSTOMA

The reproductive performances of Grey-headed Albatrosses Diomedea chry sostoma with a previous record (greater than or equal to 5 years) of c onsistent success (greater than or equal to 70% chicks fledged from eg gs laid-''top'' birds) or failure (greater than or equal to 70% of att empts failed-''bottom'' birds) were compared during 1993-1995, In 1995 , top birds arrived back at the colony significantly earlier, had sign ificantly shorter first and second incubation shifts and hatched large r chicks which grew significantly faster than bottom birds, In 1994, t op birds also had larger hatchlings with higher rates of growth than b ottom birds, In 1994, top birds had significantly higher hatching, fle dging and therefore overall breeding success than bottom birds; very s imilar trends were evident in 1993 and 1995. Chick-rearing success and all indices of chick growth suggested that food availability was high in 1995 (and 1993) and low in 1994. Therefore the superior performanc e of top birds was maintained in years of very different conditions, w ith the chick-rearing period particularly critical, A simple model (us ing published demographic parameters for Grey-headed Albatrosses on So uth Georgia) suggests that top birds would produce 2.5 more chicks ove r their lifetime than bottom birds. With the currently declining popul ation numbers, the relative contribution of top birds to the next gene ration may be even greater than this.