Changes in the waterbird community of the Lake Illawarra estuary: 20 years of research

The entrance channel to Lake Illawarra on the southern coast of New South Wales, Australia is home to over 55 species of waterbird. Between 1981 and 2003 four periods of systematic population survey were undertaken by the authors. Herein we analyse this data to examine temporal trends in individual species and foraging guilds. We found that changes in environmental conditions due to engineered habitat reduction appear to have resulted in the decrease of probing and pecking invertebrate feeders (8 species), especially trans-equatorial migrants. Conversely, indigenous invertebrate feeders appear to increase their local populations marginally through the study period. The largest overall change in populations occurred amongst diving fish-eaters, especially Little Pied Cormorant and Australian Pelican, which have increased markedly and both these species now breed locally. The loss of intertidal mud flats and saltmarsh around the southern margins of Windang Bridge appear to be the main cause for the reduction in avian invertebrate-feeder diversity through the study period.