Within ornithology my work has fallen mainly within woodland bird ecology. From 1981 to 2012 I was privileged to conduct research on the Wytham Great Tit population. Principally through ringing, I collected data over a long period to study the finely tuned adaptations of birds. This research included a long-term study of bill size and body condition (including studies of fat and muscle that can be determined visually during normal ringing/banding operations), which started during my doctoral research in the early 1980s, and a long-term study of the functions of eggshell pigmentation. Although Great Tit has conservation status of 'Least Concern' my long-term research has delivered general principles that have contributed to environmental monitoring and conservation. Hence, for example, principles of winter fattening shown in the Great Tit were found relevant when applied in studies of declining species, and the discovery that eggshell speckling in the Great Tit is related to eggshell thinning has been found relevant to studies of the effects of soil acidification on passerine birds, and of pesticides (DDT) causing eggshell thinning in raptor species. While I still run an active bird-ringing group in Oxford, since 2013 I have shifted my focus largely to ethno-ornithology.