Threatened seabirds: rat eradication on the South Barnard Islands
Sooty oystercatcher (Heamatopus
fuliginosus). Photo: Tim Holmes Introduction
During nesting, adult seabirds, their young and eggs are vulnerable to predation by introduced predators. On islands, the introduced predator that often poses the greatest threat is the black rat (Rattus rattus), a voracious nest predator. On the South Barnard Islands near Innisfail, the department/QPWS have undertaken a rat eradication program that has safeguarded the nests of many seabird species, including the Endangered little tern (Sterna albifrons) and the Rare sooty oystercatcher (Heamatopus fuliginosus ).
Introduced species
The arrival of Europeans in Australia also saw the arrival of a wide range of non-native species including, the cow, sheep, pig, cat, fox and rat, to name just a few. The black rat would have been one of the first animals to arrive with the early European ships in the late 1700s. While many introduced species allowed settlers to maintain farming methods from their countries of origin, all have impacted on their new environment in some way, and some introduced species have had significant adverse impacts on many species of native wildlife.
Sensitive island ecosystems: Islands, because they are usually small in size, are particularly sensitive ecosystems. Any additions or changes to island environments can often have lasting effects on ecosystems. The isolated nature of islands can affect the recovery of ecosystems after change, particularly as the distance between islands and mainlands often inhibits dispersal of native species. But this distance can also provide islands with protection, acting as an effective barrier against introduced species. Islands typically provide important nesting sites for many species of seabirds, including important migratory and threatened species.
The South Barnard Islands
The South Barnard Islands are located approximately 25km south of Innisfail, and consist of Sister Island (3.5ha) and the larger Stephens Island (10.5ha). They are one of the most important nesting sites in the northeast of Queensland for the bridled tern (Sterna anaethetus), as well as a nesting site for other seabirds. It is not known exactly when and how black rats arrived on these islands, but they were first identified from surveys conducted in 1999. Floods from nearby river systems may have washed the rats to the islands that lie about 5km from the mainland. The rats soon began invading seabird nests and eating eggs. Because of their high potential to devastate the island's seabird population, the department/QPWS implemented an eradication program.
Recovery actions
- The department/QPWS began a rat eradication program in 2000. This maintained rat numbers and gave EPA/QPWS staff an opportunity to confirm that there were no other terrestrial mammals present on the islands. As there were no other mammals on the islands, poisoned baits were also used to combat rats.
- Following baiting, several surveys were undertaken on the islands to check for the presence of rats. Rats are no longer known to occur on the islands.
- Although the program has been a success, rats may return to the islands, especially since the origins of the rats arrival in the 1990s remains unknown. The department/QPWS continues to monitor the islands for rats.
Last updated: 18 September 2006