Evaluating empirical evidence for decline in temperate woodland birds: A nationally threatened assemblage of species

Abstract

Quantifying the population trends of species is crucial to achieving effective conservation action. However, deriving accurate and reliable indices of change is difficult due to the paucity and complexity of population data. There is a growing need to assess the inferential status of reported trend estimates given their pertinence to evidence-based conservation policy and funding. In this review, we used a simple scoring system to assess the rigour of population assessments using Australian temperate woodland birds as a case study. These birds are widely considered to be in severe and ongoing decline at a national scale. However, we found relatively few studies that report population trends for woodland birds in the existing conservation literature (44 articles, 9% of total) and only 33 articles (7% of total) that actually attempt to measure change using population data. While we identified strong signs that the inferential status of population research on temperate woodland birds is improving, we detected serious limitations in the temporal coverage and statistical analysis of population data used in the majority (80%) of trend assessments, compromising any long-term inference about population persistence. Despite these limitations, the decline of woodland birds is referenced in over half of all Australian woodland bird conservation studies (53%), with most of the information on woodland bird status (49% of citations) sourced from relatively few, predominantly qualitative, studies of change. The paucity of research that can reliably detect trends to draw conclusions about species persistence is a concerning issue for conservation practitioners and policy makers.