The underlying aim of our paper (Tuyttens et al., 2002) was to draw attention to the desirability – for reasons of science and animal welfare – of applying the scientific method to test for effects of techniques in field biology. Therefore, we are grateful to Delahay et al. (2002) for their response which not only advances that aim, but provides us with the opportunity to elaborate on the importance of the issue. In this reply we focus first on the questions they raise about our analysis and then, second, and more importantly, we set the answers in a broader context of what we foresee as a new era of animal welfare science as a component of conservation biology.