Moult in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma

We recorded the age of individual wing and tail feathers of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma of known age and breeding status at Bird Island, South Georgia. Breeders and non-breeders of both species moult their rectrices annually. Non-breeders moult primaries biennially. In the first year of a cycle, the outer three and some inner primaries are moulted descendantly; in the next year the inner primaries are moulted ascendantly, starting from primary seven. There is a general progression to moulting equal numbers of primaries in each half of the cycle by the time breeding starts at about 10 years of age. Grey-headed Albatrosses usually moult fewer primaries than Black-browed Albatrosses, particularly as 3-year-olds, when they undertake substantial plumage change in body moult. Most secondaries in Black-browed Albatrosses have been replaced once by age 4 years. Breeding Black-browed Albatrosses continue the moult pattern established as immatures whether they fail or not, as do failed Grey-headed Albatrosses. Successful Grey-headed Albatrosses, which breed again 16 months later, moult their three innermost primaries after breeding in the remainder of the current year and, after a period when moult is interrupted, renew the remaining primaries the following year. Comparisons between species and between failed and successful birds within species indicate that moult rate is not closely linked to the length of the interval between breeding attempts. Interspecies differences are better explained by breeding latitude, with tropical albatrosses moulting twice as fast as sub-Antarctic species, possibly reflecting food availability outside the breeding season.     

Egg formation and the pre-laying period of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma at Bird Island, South Georgia

Egg composition and factors influencing egg formation were studied in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma at Bird Island, South Georgia. At nests where eggs were laid, females arrived 6–7 days after males, stayed one day during which 96% of observed copulations occurred, then departed to sea for c. 16 days in D. chrysostoma, c. 10 days in D. melanophris , returning c. two days before laying. Yolk deposition, however, lasted 21 and 20 days, and started 32 and 29 days before laying, in D. chrysostoma and D. melanophris respectively. Therefore, it is probably initiated by environmental factors not by copulation. Egg, albumen and yolk mass are significantly greater in D. chrysostoma but the proportionate composition of the species' eggs is nearly identical. Reduced differences in chick mass at hatching may reflect the longer incubation period in D. chrysostoma or relate to subsequent differences in chick growth rate.     

Activation of Choline Acetyltransferase by Salts

IONIZED salts affect choline acetyltransferase, EC 2.3.1.6 (ChA), in two important ways. They change the equilibrium between soluble and membrane-bound ChA, in preparations of ruptured nerve endings^1,2. Further, the rate of synthesis of acetylcholine by soluble ChA and the Michaelis constants for this reaction depend on the concentration of salts³. The relevance of these effects to the role of ChA in nerve function and the mechanisms responsible are unknown. Our observations clarify the effect of salts on the soluble enzyme.