Congratulations to Chris Harris and co-author Christine Madliger for having Chris’ second data chapter entitled “An evaluation of feather corticosterone as a biomarker of fitness and an ecologically-relevant stressor during breeding in the wild“ recently accepted in Oecologia. The field of using feather corticosterone as a biomarker of individual responses to environmental stressors in rapidly taking off, and yet has received fairly little critical evaluation with regards to its links to performance and fitness. Chris’ work used a manipulative, multi-year dataset tracking individuals across stages and years to ask whether fCORT provides a reliable, easy-to-interpret measure of stress during reproduction. Perhaps not surprisingly, Chris found very context-dependent answers to these questions and little support for fCORT being able to pick up a major stressor during breeding. We hope this work will enable researchers to start to better appreciate the capability of  this trait as a  biomarker of environmental stress. Great work as always Chris.