Justification of Red List Category
Although this species may have a restricted range, it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population size has not been quantified, but is very numerous within its range and is regarded as an agricultural pest.
The population trend is difficult to determine because of uncertainty over the impacts of habitat modification on population sizes.
This species formerly occurred on mainland Australia but disappeared around 4,700 years ago, roughly coinciding with the arrival of the dingo Canis familiaris. It is now restricted to Tasmania, Australia, although the species was introduced to Maria Island, off east Tasmania, in 1969.
The species is found in a variety of habitats from open pasture and crops to permanent and seasonal freshwater wetlands. It requires short-grazed pasture for foraging and is currently dependent on swards maintained by introduced species (sheep, cattle and rabbits); swards were formerly maintained by grazing marsupials and by fire. It always breeds near water, usually from August-November, and mostly feeds on seeds and leaves, varying with the availability of plant species. It is flightless, making it very vulnerable to introduced predators.
The recent spread of foxes (Vulpes) to Tasmania is of concern, and although they are still scarce it is likely that they will impact upon T. mortierii in the long term.
Text account compilers
Butchart, S., Ekstrom, J., Fisher, S. & Harding, M.
BirdLife International (2023) Species factsheet: Tribonyx mortierii. Downloaded from http://www.birdlife.org on 23/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/03/2023.