Hans Duncker’s private and scientific life has been reconstructed from a variety of sources. These included obituaries (usually all too brief), records kept at the Staatsarchiv in Bremen (including the typescript of the Allies Interview and his ‘personal record’) and his own publications. A handful of letters (mainly from the 1940s and 1950s) exist and are held in the Staatsarchiv and the Übersee-Museum in Bremen. There were no diaries that I could find and I was unable to locate any members of Duncker’s family. Fortunately Duncker was a prolific writer and produced both scientific and popular accounts of his work and the latter often include information of a more personal nature. On the other hand, many of these popular accounts were published in bird-keeping magazines or newspapers (such as Kanaria, which came out weekly) but are no longer published and copies from the 1920s and 1930s are now extremely few and far between. I talked to a few people who were contemporaries of Duncker and knew of him, but only one (Professor Gerd von Wahlert) had met Duncker. Throughout the text I have tried to make it clear, usually by identifying a specific reference, where I have evidence for a particular event taking place. Rather than citing every source of information on Duncker here, anyone interested in these should consult Birkhead, Schulze-Hagen and Palfner (2003). Where no specific information exists I have occasionally used my own judgement, based on my own bird-keeping and scientific experience, to infer what might have taken place. I have tried to make it clear where I have done this.