More than 20,000 waterbirds have been recorded on Forrestdale Lake. It regularly supports more than 1% of the national population of five shorebirds: red-capped plover (with up to 1,300 recorded at any one time), black-winged stilt (3,840), red-necked avocet (1,113), long-toed stint (up to 80), and curlew sandpiper (2,000). In some years it supports more than 10,000 ducks, including Australian shelduck (up to 1,650 counted), Pacific black duck (5,500), grey teal (9,000), Australasian shoveler (2,000), and hardhead (1,053). The lake is one of the few sites in Western Australia where little ringed plover and little stint have been recorded more than once, and it is the only location in the state where white-rumped sandpiper has been recorded.