A Threatened Bird Index for Western Australia

Here, the national Threatened Bird Index (TBX) is drilled down to report on information relating to trends for threatened birds in Western Australia (Figure 1A). In its first iteration, this index incorporates data from 14 threatened bird taxa (Vulnerable, Endangered or Critically Endangered under the EPBC Act and/or as assessed by BirdLife Australia - see Table 1). More data will be added as they become available every year allowing the index to grow. The index shows the estimated yearly change in relative abundance of threatened bird species in relation to a baseline year, for which 1985 was chosen, where the index is set to 1.0. The baseline is flexible and can be chosen based on the specific needs of conservation managers. Changes in the index are proportional—a value of 0.5 indicates the multi-species relative abundance is 50% below the baseline value; a value of 1.5 indicates 50% above baseline. In 2015, the WA TBX value given the current data is 0.37. This suggests that the relative abundance of threatened birds for which we have information has decreased by 63% between 1985 and 2015. While the overall index value in 2015 is 0.37, individual species have TBX values between 0.19 (a 81% decrease) and 0.77 (a 23% decrease). In the same context, the national TBX shows a decrease of 52% in the compiled data.