When feathers fell from fashion: Unpacking the end of the UK plumage trade

By the mid-twentieth century, the previously booming bird feather trade was a fraction of what it was in its prime, allowing for the recovery of many bird species. We use a qualitative impact evaluation method to assign probable causality to different drivers of this change, ultimately providing expert-supported explanations of how a large-scale behaviour change was enacted to benefit conservation. We outline a method for applying general elimination methodology plus (GEM+), accounting for different facets of evidence reliability, to generate conclusions on most strongly supported causes of change. GEM+ addresses calls for an increase in impact evaluation in conservation, which will require a range of tools, including qualitative, to fill. Analysis of diverse evidence using GEM+ suggests that conservation advocacy, interacting with broader contextual factors, plausibly contributed to a shift in public behaviour that was instrumental in the passage of the Plumage Act and the subsequent end of the trade. This case study has widespread implications for designing effective behaviour change campaigns, as well as providing a framework for conducting impact evaluations in a range of conservation settings.