Lake Gregory is located on the edge of the Great Sandy desert, Western Australia. It has contained water for all but 2 or 3 years since 1969 and the estimated waterbird population in 1988, when the lake appeared to act as a drought-refuge, was 650 000 birds. During the last 20 years, 73 waterbird species have been recorded at the lake, 21 of them breeding. Despite the abundance of water and waterbirds in recent years, rainfall records suggest Lake Gregory was mostly dry between 1930 and 1968. Assessments of its conservation significance during this 'dry phase' would have been very different from the current assessment. Decisions about the importance of arid zone wetlands need to recognize that conservation values can vary enormously, depending whether wetlands are flooded or dry, and that ideal flooding conditions may occur at intervals of several decades. Factors influencing the number of waterbird species at Lake Gregory include the amount of water in the lake, the amount of water elsewhere, the extent of inundated trees and shrubs, and, possibly, the taxonomic range of available food items
