Population trends of woodland bird species in the Clarence Local Government Area, southeast Tasmania

Monthly monitoring was initiated in 2015 and continued for 10 years at 20 peri-urban sites in the Clarence Local Government Area (LGA) in southeast Tasmania to identify the trajectories of bird populations. A total of 869 surveys were undertaken and 78 bird species recorded. The 2 ha survey sites were in a range of locations and monitored in the mornings for 20 minutes during the post-breeding season (January–April). There was a statistically significant decrease of 21% for the decade in the number of species recorded per survey, indicating a long-term decrease in species diversity at the survey sites. Nine of the 21 most frequently recorded species (43%) had relatively stable populations over the 10 years. The predominant trend of the remaining species was a decrease, with six species’ decreases statistically significant. Three species increased, one statistically significantly. Of greatest concern was the decrease of two Tasmanian endemic species: dusky robin and black-headed honeyeater, with both decreases highly significant at greater than 70% for the decade. The strongly decreasing species were small insectivores, consistent with global trends, attributed to decreases in insect populations. Many factors associated with climate change and progressive forest degradation potentially contribute to these losses and may be particularly severe in the study area, which already has a below average rainfall. These decreases in species diversity and abundance in a local bird community are of alarming magnitudes and the cause(s) need to be identified and addressed.

Key Words: bird population trends, Clarence, Tasmania, endemic bird decreases, dusky robin.