Jürgen Aschoff, a Corresponding Fellow of the AOU since 1976 and an Honorary Fellow since 1981, was born 25 January 1913 in Freiburg, and died there on 12 October 1998. The son of a world-renowned pathologist, Jürgen studied medicine at the University of Bonn, then moved in turn to Göttingen, Würzburg, and Heidelberg. He was primarily a physiologist and a pioneer in biological rhythms, but various circumstances led him to undertake bird studies. The more general physiological and chronobiological aspects of his career have been commemorated in Nature 396:418 (1998) and Journal für Ornithologie 140:384–387 (1999); this memorial will emphasize his ornithological achievements.
That Aschoff developed an appreciation of birds as ideal research objects—not least for his own investigations of circadian periodicity—had six main causes. First, he learned from his close associate Gustav Kramer, who discovered the sun compass in birds, that birds compensate for the sun's movement across the sky by reference to their endogenous circadian clock. This insight opened new perspectives for himself as a chronobiologist and initiated a collaboration with Kramer when both became Scientific Members of the Max Planck Society in 1958. Tragically, Kramer died within a few months, and the research had to be undertaken with other partners. Second, a number of scientists with ornithological interests assembled around him: Klaus Hoffmann and Eberhard Gwinner became assistant researchers in his institute. Third, after Kramer's death, Jürgen assumed the directorship of the Vogelwarte Radolfzell (after the end of its Rossitten era, it was incorporated into the Max Planck Institute for Behavioral Physiology, of which Aschoff's group was a part). This brought him into contact with Hans Löhrl, Gerhardt Zink, Gerhard Thielcke, and myself, among others. Fourth, in 1955, in one of his most important reviews (on the annual periodicity of reproduction in warm-blooded animals), Jürgen had acknowledged the vast abundance and significance of ornithological data; at a mature age he became a committed “birdman” who even developed ambitions in the direction of field ornithology. Fifth, he found a source of encouragement in his admiration for men such as Donald Farner, Lars von Haartman, Konrad Lorenz, Niko Tinbergen, and for the inexhaustible efforts of thousands of volunteers who contributed to the field work. Sixth was the combination of his scientific brilliance and his Prussian ability to define and concentrate on a specific goal. Not only did these give impetus to major research projects of his coworkers, such as the “Warbler Program,” the “Mettnau-Reit-Illmitz Program,” and the “Atlas of Song Bird Migration Project,” but Aschoff himself took on responsibilities of importance both nationally and internationally. He was a major originator of the international conference for the “Co-ordination and Encouragement of Amateur Ornithology” that was held in 1971 in Tring, England, and that produced far-reaching incentives and standardization. He also served from 1968 to 1973 as treasurer of the German Ornithological Society and contributed as Plenary Lecturer and Organizer to a number of International Ornithological Congresses, in particular to the 18th IOC held in Moscow in 1982, where he served as Chairman of the Scientific Program Committee.
The quintessence of Aschoff's ornithological achievements can be summarized as follows: as an outstanding scholar and world citizen, he helped to make the ornithology of his time a highly respected science, as did his close friend Donald Farner in the USA.