New study points to the global significance of the Plains-wanderer

Can you spot Australia's most unique bird?
Terrick Terrick National Park
Photo: John Morgan

The Plains-wanderer has for some time been known to be a member of Australia’s ancient avifauna and its nearest, albeit distant, relatives are seedsnipe from South America.  It is the sole member of a Family of birds called the Pedionomidae. It's a species typically confined to native grassland habitats in eastern Australia and, unfortunately, one of the most endangered species of those grasslands. It should be a flagship for conservation and new research tells us why!

Recently, Jetz et al. (2014) published a major review of the world’s 9,993 recognised bird species to determine which species we can least afford to lose in the current extinction crisis if maximum global phylogenetic diversity is to be maintained.  Phylogenetic diversity is a measure of biodiversity which incorporates phylogenetic difference between species and phylogenetic analyses have become essential to research on the evolutionary tree of life. The concept of phylogenetic diversity has been rapidly adopted in conservation planning.

Jetz et al. (2014) developed a hierarchy based on how isolated a species is on the phylogenetic tree which they termed ‘evolutionary distinctness’.  They also included global geographic range, and global endangerment in their metrics.  The summary metric that Jetz et al. (2014) used to rank the world’s birds combines evolutionary distinctness and extinction risk. 

By their calculation, the Plains-wanderer is ranked:
 #1 among Australian birds and #4 in the world!!

As such, these analyses highlight we can ill-afford to lose the species, yet current data suggest that significant declines are being observed, and it's not entirely clear why.

The two strongholds of the Plains-wanderer are the semi-arid (or xeric) native grasslands of the Riverina region of NSW and Victoria’s Northern Plains.  Monitoring in NSW during 2001-2012 has found that the population size has declined by 75% during droughts, then recovered slightly during benign years, and was then recorded at record low levels during the very wet years of 2011-12.  The population has remained at very low levels for over a decade, and this is cause for considerable concern. In Victoria there has been monitoring on Terrick Terrick NP and nearby private land over five years (2010-14).  Numbers declined by >90% during 2011-12 in the wet years (perhaps because breeding was negatively affected, while thickening of grasslands has reduced occupyable habitat) and the numbers have remained at historically low levels.

If ever there was a need to monitor the dynamics of a species of conservation concern, whilst also monitoring its habitat suitability and key determinants of mortality risk (e.g. predation),  then the Plains-wanderer would seem an essential candidate species. Good, basic scientific research is needed to answer simple questions: how long do birds live; are population dynamics cyclic; can suitable habitat be successfully created from scatch? In some respects, a metric of the success of grassland conservation and management will be that species like the Plains-wanderers can be maintained in their habitat, and that their numbers grow rather than decline.

Thanks to David Baker-Gabb for alerting me to the evolutionary distinctiveness of the Plains Wanderer, and for providing information on the population trends of this species.

Reference

Jetz, W, Thomas, G H, Joy, J B, Redding, D W, Haartmann, K and Mooers, A.  2014.  Global distribution and conservation of evolutionary distinctness in birds.  Current Biology (2014), http://dx.doi.org/10.1016/j.cub.2014.03.011.