Waterbirds on an adjacent freshwater lake and salt lake in arid Australia

Abstract

Aerial surveys of waterbirds were made on Lake Wyara (salt) and Lake Numalla (freshwater) in arid Australia, every three months, 1987–1989. These lakes were significant sites for conservation of waterbirds. Aerial counts were on average 42 000 waterbirds (2600–113500), including at least 41 species. In March 1988, total numbers probably exceeded 280 000. More than half the population of freckled duck Stictonetta naevosa may occur on the lakes. Although only 3 km apart and similar in size, the salt lake had about ten times more waterbirds (mainly ducks, herbivores, small wading birds) than the freshwater lake (mainly piscivores, large wading birds). Differences in waterbird communities between the lakes were attributable to food resources. There were larger numbers of planktonic invertebrates and more macrophyte vegetation in the salt lake than in the freshwater lake while the freshwater lake contained fish and shrimp populations.