The normally dry, salt encrusted bed of Lake Torrens was transformed into a lake following significant local rain which occurred in April this year. Members of Friends of Shorebirds SE have been monitoring the large flock (150 ??? 200,000) of Banded Stilt that has been utilising the hypersaline conditions of the lower Coorong for the last 8 years. Iain Stewart, who had been tracking water flows throughout the arid interior since the floods in northern Australia, reinforced by David Dadd???s report of the absence of birds in the Coorong, immediately realised the significance of the water in Lake Torrens. A call went out to members and DEH Coorong staff for news of the Coorong flock. The last documented sighting of a significant number was on 5th April. The Department for Environment and Heritage, South Australia, was contacted stressing the urgency of the situation ??? high in every-one???s thoughts was the massive predation that had occurred at Lake Eyre in 2000, and the need to locate and protect a breeding colony as soon as possible. They firstly flew over the Coorong and confirmed the missing birds and then subsequently made a search of a number of inland lakes from Lake Eyre to the south. In early May they located a large colony of around 140,000 Banded Stilt which appeared to be nesting on an island in Lake Torrens. This was a very special event as this species had not had an extensive breeding event since the one at Lake Eyre South in 2000 although a small attempt was recorded in the Coorong in 2006.
?? Ken Gosbell
This species requires small isolated islands in large ephemeral inland salt lakes where the influx of fresh water stimulates the dormant brine shrimp and other small crustaceans to hatch and reproduce. Such conditions are erratic given the nature of inland Australia and Banded Stilts are known to have bred in SA only seven times in the last 70 years.
In response to the discovery of this breeding colony, the Department for Environment and Heritage sent in an expedition of ecologists and rangers in early May, led by Alex Clarke of the Port Augusta office of DEH. Their objective was to observe and check for any excessive predator activity. They were able to confirm the colony had 140,000 – 150,000 birds and that they were witnessing probably the largest breeding event on record with up to 200,000 chicks produced. Even better news was the fact that predation activity by Silver Gulls was minimal and within natural bounds. It was also observed that following the first hatching, the colony split with half moving to a northern island and the remainder laying a second clutch of eggs in the original colony.
?? Ken Gosbell
The AWSG, VWSG and Friends of Shorebirds SE, were invited to participate in a second expedition timed to coincide with the second hatching to record observations and to attempt to place bands and coloured leg flags on some of the chicks. The latter was aimed at finding more about the movements of these birds including any possible movement between the WA and southeastern Australian populations. Accordingly 4 of us (Maureen Christie, Iain Stewart, David Hollands and Ken Gosbell) accompanied a team of rangers and ecologists from the Coorong office of DEH (Simon Oster, Clare Manning and Chris Thompson). We set out from Port Augusta and camped on the shores of Lake Torrens from 14 ??? 18 June when we returned to Port Augusta. To view this body of water almost 200km long and up to 30km wide, surrounded by gibber and desert, listening to a colony of Banded Stilts almost 3km away was an amazing experience.
The colony occupied about half of a small island some 320m by 200m which was located 2.7km from the shoreline campsite. Hence a walk through water 20 ??? 30cm in depth for this distance to get to the colony each day was more than sufficient exercise. The colony was much reduced by the time we arrived with less than 10,000 birds in it. It was located on sandy patches interspersed with low salt bush (Atropex sp), Nitre-bush (Notraria sp), Samphire (Sarcoconia sp), Rhagonia and other plants. Birds were nesting in scrapes which were at a density of 10 ??? 15 per square metre and were sitting on 2 to 4 eggs. Some 30% of the colony had been abandoned probably due to disturbance by a fox and/or dingo which had killed quite a few adult birds. We assessed that chicks from the second clutch had been hatching for the last week and this continued at a reasonably constant rate for the days we were there. When the chicks are 1 or 2 days old the adults take them across the stony beach and introduce them to the water. The rate of chicks being taken to the water varied from 50 to 350 chicks per hour and we saw very few actually taken by gulls. However, as the colony thinned out, more gulls were entering the colony.
One of the inspiring sights was to see the adults shepherd their family of 2 ??? 4 fluffy white/grey down covered chicks to the water, negotiate past the line of gulls and reach the open water where they amalgamated with other family groups to form cr??ches. The largest cr??che we observed was 40 but as they were moving some distance (several kms) to feed we suspect that even larger cr??ches were being formed which is their normal behavior.
?? Ken Gosbell
Several attempts were made to band chicks while they were in their family groups in the water. This was a tedious process due to adults appearing to abandon the chicks when captured. This meant great care was needed to reunite chicks with adults who were caring for cr??ches. Because of these constraints we were only able to band and leg flag 54 chicks. So, if you see a Stilt with orange/yellow on the Left tibia it is a very special bird and we need to hear about it. We are also interested in observations of juvenile stilts ??? recognisable by their grey legs.?? The first clutch is thought to have started hatching on the 10th May.?? Allowing 50 days to fledge, they could be arriving at a wetland near you any day!?? Indeed news of the arrival of adults is also of interest as it will help us understand how they disperse after such a large breeding event. One of the highlights of our visit to the colony was when Clare spotted a bird with flags on its right leg which was the result of the banding undertaken by Maureen and her team in the Coorong in 2006.
Overall this was an exciting event which at this stage appears to have been extremely successful for this enigmatic species. To have observed and photographed this unique event combined with the experience of witnessing the way in which outback Australia comes alive with water was very special. We would like to thank the staff of DEH SA for their consideration, co ope
ration and assistance on site; it was a great team effort. We also thank our flag making teams for making a large number of flags at short notice.
It should also be noted that a small breeding event also took place on Lake Eyre where some 5,000 birds nested. This was reported in the media earlier this month.
Although we have increased our knowledge of one of the most interesting of our resident species through the observations of this event, there is still much to learn. Just how did those birds who were happily feeding in the Coorong know that suitable breeding conditions had been created 1000 kms away? Maybe in time we will learn.