On the occasion of Ernst Mayr's recent passing, it is interesting to examine his career with two themes in mind: (1) the role of accidental events that fell his way and how he responded to them, and (2) his work within and ornithology and how each affected the other. Most important is that his central interests as a naturalist profoundly influenced all his empirical and theoretical work. His outlook as a naturalist, his broad empirical studies, and his ornithological knowledge permitted him significant new insights into the history and philosophy of biology. He showed that an understanding of the biology of a group of organisms, such as birds, provides a valid foundation for advances in biology. Resumen. Con motivo del deceso reciente de Ernst Mayr, es interesante examinar su carrera teniendo en mente dos temas: (1) el rol de los eventos accidentales que interrumpieron su camino y como el respondio a los mismos, y (2) su trabajo dentro y fuera de la ornitologia y como uno afecto al otro. Lo mas importante es que su interes central como naturalista influencio profundamente todo su trabajo empirico y teorico. Su perspectiva como naturalista, sus estudios empiricos amplios y su conocimiento ornitologico le permitieron brindar significativos puntos de vista nuevos en cuanto a la historia y la filosofia de la biologia. El mostro que el entendimiento de la biologia de un grupo de organismos como las aves brinda una base valida para avances en biologia. Long ago on 5 July 1904, just six months after the first powered flight by humans at Kittyhawk, North Carolina a person was born in a small town in Bavaria, Germany, who was to earn fame through his studies of another group of flying creatures. To put that date in proper perspective for ornithologists, it was the year before the 4th International Ornithological Congress in London and five years before the publication of the last volume of R. Bowler Sharpe's A Hand-list of the Genera and Species of Birds. And the American Ornithologists' Union (AOU) had just attained its majority, having reached its 21st year. I refer, of course, to Ernst Walter Mayr, who celebrated his 100th birthday on 5 July 2004 and who passed away on 3 February 2005 at the Carleton-Willard Village, Bedford, Massachusetts, where he had lived since September 1997 (Bock 2005). 'Revised from Bock 2004a. 2E-mail: wb4Ciocolumbia.edu Ma y ornithologists have had long lives and others have reached the century mark, including Wilhelm Meiseanother doctoral student of Professor Erwin Stresemann and a student colleague of Ernst Mayr in Berlin during the mid-1920s. Although Mayr turned to other areas of inquiry later in his career, he trained as an ornithologist, made his name as an ornithologist, and remained most interested in avian biology. Other areas of study such as evolution, the hist ry of biology, and the philosophy of biology may claim Mayr as one of their own, but ornithology retained his primary allegiance. Some years ago, while discussing several earlier workers, Mayr made the comment to me that Stresemann never ventured scientifically ornithology, a remark I found very interesting. On further reflection, it was clear that Stresemann was, in that way, similar to many well-known students of avian biology. Mayr, on the other hand, went well beyond the boundaries of ornithology and was just as successful in other fields of work. It is this venturing outside that makes Mayr's career so fascinating.