David Baker-Gabb, ecologist
and Mark Antos, Parks Victoria
In the 16 years 1994-2009 there was only one year with rainfall slightly above the long-term average, whereas there were four droughts among the series of 15 below average rainfall years on then Northern Plains. The current stronghold of the Plains-wanderer in Victoria is the Northern Plains, which are comprised of the Patho Plains west of Echuca and the Avoca Plains west of Kerang.
Following this series of dry years, separate surveys by David Baker-Gabb and Mark Antos revealed moderately high numbers of Plains-wanderers on the Northern Plains in 2010 (Figure 1).Surveys for Plains-wanderers and monitoring on the Patho Plains during 2010-14 indicated that there had been about a 95 per cent decline in the Plains Wanderer’s relative abundance there since 2010. This population crash was precipitated by historically high rainfall throughout south eastern Australia in late 2010 and for much of 2011. This resulted in widespread flooding where water covered much of thegrasslands for weeks and was followed by a massive surge in grassland biomass which persisted for up to three years.
This rampant growth was not initially mitigated by an effective management response such as increasing grazing pressure or burning. Most private paddocks and reserves on the Northern Plains developed an almost uniformly dense tall sward of grass that severely disadvantaged Plains-wanderers, which must have sparse grass to survive range of other threatened grassland fauna species were equally disadvantaged by these conditions.
Very low numbers of Plains wanderers were also recorded on the Avoca Plains in 2012. None were recorded in 2014 and 2015. There were no records of breeding anywhere on the Northern Plains between 2011 and mid-2014. In late 2014 and early 2015, we recorded 39 Plains-wanderers on the Patho Plains.
This is merely an incipient recovery because encounter rates in 2015 were still less than half those of 2010. Moreover, breeding was recorded in just four (16%) of 24 paddocks surveyed, and only seven of the birds were adults, the rest (82%) were juveniles or chicks. These results suggest that the emerging recovery has not been fuelled by immigration to the area, but instead, by the very few breeding adults left on the Patho Plains after the major declines of the past four years.
These few remnant birds have bred remarkably well. Indeed, different age cohorts of chicks and juveniles indicate that the remnant adults bred successfully in spring 2014, again in the summer of 2015, and then again in autumn 2015.This level of ongoing breeding has not been recorded before in Northern Victoria.