Declining but not (yet) threatened: A challenge for avian conservation in Australia

Threatened species receive much attention in conservation science and practice. Species currently declining, but not yet listed as threatened, also deserve consideration to reduce their risk of sliding towards extinction and to maintain their functional roles in ecosystems. Information on declining bird species in Australia is available from four main sources: national databases, syntheses of historical change, regional monitoring programmes and summaries for guilds of species. Many species show evidence of decline; declines of species are occurring nation-wide, and they are ongoing. Trends for individual species vary geographically; they may be declining in part of their range but stable elsewhere. Common trajectories of population decline include: (a) a downward linear trend; (b) a marked downturn, sustained at a lower level; and (c) fluctuations through time associated with episodic events (e.g. drought) and incomplete recovery. Ongoing declines affect ecosystems through reduced species richness, homogenisation of bird communities, changes to interspecific interactions and ecosystem services, and contributing to extinction debt. Improving the conservation outlook for declining species requires systematic monitoring to know where, when and how much decline is occurring, together with protection of critical habitats and source populations, ambitious programmes of restoration, and identification and effective control of threats. Responding to declining species offers opportunities for community engagement, monitoring and action at a local and regional level. New ways are needed to incorporate such species in conservation planning and environmental regulation at a regional scale, to give them greater visibility and avoid local declines accumulating until taxa become nationally threatened.