Climate-mediated changes to grassland structure determine habitat suitability for the critically endangered plains-wanderer (Pedionomus torquatus)

The critically endangered and iconic plains-wanderer (Pedionomus torquatus) is phylogenetically distinct and endemic to south eastern Australia, and is a high conservation priority. Furthermore, it relies on critically-endangered native grasslands for its survival, which vary temporally in structure and hence do not always provide suitable habitat. To manage the remaining native grasslands appropriately, it is essential to understand the temporal and spatial dynamics of plains-wanderer habitat preferences. We monitored plains-wanderers and habitat measurements for nine years to link habitat preferences to specific elements of grassland structure. We also observed habitat selection by plains-wanderers at two spatial scales – sites (paddocks) and at microsites (immediate vicinity of the birds). The plains-wanderer population declined rapidly after a dramatic increase in native grass cover in 2011, and recovery of the population since then has been slow. In 2015/16, plains-wanderers were generally encountered at microsites with higher bare ground and cryptogam cover. However, at the site scale, paddocks with plains-wanderers had similar cover of native grass and bare ground than those without plains-wanderers. The results suggest that observation of highly-localised habitat components alone may mask aspects of the habitat selection occurring at larger spatial scales. Plains-wanderers may require areas of denser perennial grass for nesting and shelter, as well as access to the open areas where they are commonly encountered. We discuss how private land used for commercial grazing may be crucial to plains-wanderer conservation. The results also prompt consideration of how we measure and interpret habitat selection for grassland birds globally.