Waterbirds: Indices and Fluctuations in Dry-Season Refuge Areas, Northern Territory

Abstract

Results are presented of a weekly census carried out on Fogg Dam from April 1970 until January 1972, with additional information for adjacent dams and lagoons from 1967 to 1971. General seasonal fluctuations, as indicated by data from 39 species, are evaluated by use of sums of monthly means, species richness equitability and comparative index (Qs) values for Fogg Dam in 1970-71. The summation of monthly means of these species was correlated with species richness. The seasonal expansion and contraction of the wet habitat seems to be the most important factor controlling fluctuations in numbers. When conditions were highly favourable over wide areas, numbers of all species in the census areas were low, indicating its status as a refuge. Anseranus semipalmata appears to have an important role in clearing vegetation and so modifying the environment for other species.