The influence of climate variability on numbers of

Authors: Lynda E Chambers Richard H Loyn

Publish Date: 2006/01/25

Volume: 50, Issue: 5, Pages: 292-304

PDF Link

Abstract

Seasonal and annual movements of Australian waterbirds are generally more complex than those of their Northern Hemisphere counterparts and longterm data are needed to understand their relationships with climatic variables This paper explores a longterm 1973–2002 set of waterbird counts from coastal Victoria and relates them to climatic data at local and continental scales Three species Black Swan Cygnus atratus Whitefaced Heron Egretta novaehollandiae and Grey Teal Anas gracilis were chosen for this analysis Black Swans have large local breeding populations near the study region Whitefaced Herons have smaller local breeding populations and Grey Teal breed extensively in ephemeral inland floodplains such as those in the MurrayDarling Basin All showed significant relationships with streamflow regional rainfall and the Southern Oscillation Index SOI at appropriate scales and timelags with streamflow explaining the most variance Black Swans showed a strong seasonal cycle in abundance and local climate variables had the greatest influence on the counts Numbers were positively correlated with streamflow in southern Victoria three to six seasons before each count Broaderscale climatic patterns were more important for the other two species Numbers of Whitefaced Herons were positively correlated with streamflow or rainfall over various parts of Australia seven to nine seasons before each count Numbers of Grey Teal showed weak seasonal cycles and were negatively correlated with rainfall in Victoria or the MurrayDarling Basin in the seasons before or during each count and positively with streamflow in the MurrayDarling Basin 15–18 months before each countStreamflow data were kindly provided by a number of state authorities Department of Infrastructure Planning and Environment Northern Territory Department of Primary Industries Water and Environment Tasmania Department of Natural Resources and Mines Queensland Department of Water Land and Biodiversity Conservation South Australia Rubicon Systems Australia Pty Ltd Victoria Sydney Water New South Wales Water and Rivers Commission Western Australia Mike Matheson of the Bureau of Meteorology provided assistance in obtaining information on stream flows Wasyl Drosdowsky for the provision of the SOIrainfall plots Dörte Jakob for assistance in producing the drainage division plot and the National Climate Centre provided the SOI and rainfall dataThe authors wish to acknowledge the insightful comments made by Dr Ian Norman of the Arthur Rylah Institute for Environmental Research and Drs Scott Power and Bertrand Timbal both of the Bureau of Meteorology on an earlier draft of this paper The paper was further improved by comments from two anonymous reviewers

Keywords: