Influence of phylogeny, diet, moult schedule and sex on heavy metal concentrations in New Zealand Procellariiformes

Abstract

Mercury, cadmium, zinc and copper concentrations were analysed in the liver and kidney tissues of 14 species of albatross and petrel. These birds were obtained as by-catch of the long-line tuna fishing industry in New Zealand waters, and provided a unique opportunity to compare heavy metal accumulation in a group of closely related species. Mercury levels in the liver of the wandering and royal albatrosses were among the highest recorded for free-living birds. In multiple regression analyses, much of the inter-specific variation in cadmium and mercury levels was related to the importance of Crustacea in the diet, to phylogeny, or to the duration of the moult cycle. Species in which crustacea constituted >33 % of the diet had significantly lower cadmium concentrations in liver tissues, and mercury concentrations in both liver and kidney tissues, than those in which birds consumed mainly or entirely squid and fish. This accords reasonably well with information on relative mercury and cadmium content of prey species. After accounting for dietary variation, Procellariidae (petrels, shearwaters and prions) and Hydrobatidae (storm petrels) still exhibited higher cadmium concentrations in the liver than Diomedeidae (albatrosses). In addition, albatrosses which took more than a year to moult accumulated higher mercury concentrations in their livers, probably because of a restricted ability to excrete mercury into growing feathers.