IUCN greatly underestimates threat levels of endemic birds in the Western Ghats

- Range maps used by IUCN for threat assessment are inaccurate and mostly overestimated.
- Citizen science, georeferenced ecological data, and distribution modeling allow accurate range estimates.
- We found the ranges of 17 of 18 Western Ghats endemic bird species overestimated.
- We also found 10 of those species requiring an uplisting of their IUCN threat status.
- Methods used here to refine range estimates have conservation implications for taxa worldwide.

The validity of the threat status assigned to a species by the International Union for Conservation of Nature's (IUCN) Red List relies heavily on the accuracy of the geographic range size estimate for that species. Range maps used to assess threat status often contain large areas of unsuitable habitat, thereby overestimating range and underestimating threat. In this study, we assessed 18 endemic birds of the Western Ghats to test the accuracy of the geographic range sizes used by the IUCN for their threat assessment. Using independently reviewed data from the world's largest citizen science database (eBird) within a species distribution modeling framework, our results show that: (a) geographic ranges have been vastly overestimated by IUCN for 17 of the 18 endemic bird species; (b) range maps used by IUCN contain large areas of unsuitable habitat, and (c) ranges estimated in this study suggest provisional uplisting of IUCN threat status for at least 10 of the 18 species based on area metrics used by the IUCN for threat assessment. Since global range size is an important parameter for assigning IUCN threat status, citizen science datasets, high resolution and freely available geo-referenced ecological data, and the latest species distribution modeling techniques should be used to estimate and track changes in range extent whenever possible. The methods used here to significantly revise range estimates have important conservation management implications not only for endemic birds in the Western Ghats, but for vertebrate and invertebrate taxa worldwide.

71