A Threatened Bird Index for Tasmania

Date: 27, Nov, 2018
Author(s):   Elisa Bayraktarov
Publisher: TSR Hub

The national Threatened Bird Index (TBX) is drilled down to report on information relating to trends for some threatened birds in Tasmania (Figure 1A). In its first iteration, this index incorporates data from 14 threatened bird species or subspecies (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 each 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. However, later baseline years are also available to support the specific needs of conservation managers and can be selected via the web-app. 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 Tasmanian TBX value given the current data is 0.61. This suggests that the relative abundance of threatened birds for which we have information has decreased by 39% between 1985 and 2015. While the overall index value in 2015 is 0.61, individual species in the index have TBX values between 0.31 (a 69% decrease) and 1.22 (a 22% increase). The national TBX currently shows a decrease of 52% in the compiled data.