WATERBIRDS ON AN ADJACENT FRESH-WATER LAKE AND SALT LAKE IN ARID AUSTRALIA

Aerial surveys of waterbirds were made on Lake Wyara (salt) and Lake N umalla (freshwater) in arid Australia, every three months, 1987-1989. These lakes were significant sites for conservation of waterbirds. Aer ial counts were on average 42 000 waterbirds (2600-113 500), including al least 41 species. In March 1988, total numbers probably exceeded 2 80 000. More than half the population of freckled duck Stictonetta nae vosa may occur on the lakes. Although only 3 km apart and similar in s ize, the salt lake had about ten times more waterbirds (mainly ducks, herbivores, small wading birds) than the freshwater lake (mainly pisci vores, large wading birds). Differences in waterbird communities betwe en the lakes were attributable to food resources. There were larger nu mbers of planktonic invertebrates and more macrophyte vegetation in th e salt lake than in the freshwater lake while the freshwater lake cont ained fish and shrimp populations.