Image right: Ulisse Aldrovandi, from the frontispiece his Ornithologiae, vol. 2 (1600).

In the second of his three-volume Ornithologiae (1599-1603), the Italian naturalist Ulisse Aldrovandi (1522-1605) reported that in his youth, he had seen this “monstrous” rooster, depicted at the left, with a “quadruped’s tail and a chicken’s crest…at the palace of the Most Serene Grand Duke of Tuscany, Francesco Medici.”

Why not take Aldrovandi at his word? He was certainly a credible source of information. As a young man, he had studied law, philosophy, logic and mathematics at the universities of Bologna and Padua. He completed a degree in medicine and philosophy in 1553, and began teaching logic the following year. His interests soon shifted to natural history, however, and in 1561 Aldrovandi became the first professor of natural philosophy at the University of Bologna. As a naturalist, Aldrovandi proved to be a terrifically prolific scholar: in addition to his three-volume book on birds, Aldrovandi wrote treatises on insects (De animalibus insectis, 1602) fish (De piscibus), on the remains of bloodless animals (De reliquis animalibus exanguibus), as well as a natural history of serpents and dragons (Historia serpentum et draconum, 1640)—one of his last works—not to mention hundreds of treatises that were not published during his lifetime. At his instance, the senate of Bologna established in 1568 a botanical garden, of which he was appointed the first director. About the same time he became inspector of drugs, and in that capacity published in 1574 a work entitled Antidotarii Bononiensis Epitome, which formed the model for many subsequent pharmacopoeias. Aldrovandi also established a botanical garden in Bologna. In the course of his long career as a naturalist, Aldrovandi assembled one of the largest zoological collections anywhere in Europe, with over 18,000 specimens, according to a description written in 1595. Linnaeus recalled him fondly as the “father of natural history.”

So, Aldrovandi was nothing if not a keen observer of the natural world and an authoritative source of information about its phenomena. If Aldrovandi reported the existence of rooster with a “quadruped’s tail,” who would doubt him?

In Aldrovandi, two worlds intersect—one in which ancient texts still exerted a powerful authority on naturalists, but also on in which precise observation of natural phenomena is fast becoming the basis for the accumulation of new, scientific knowledge about the world. Thus Aldrovandi could believe that a monstrous rooster really had existed; Aldrovandi's own observations of natural deformities seemed only to confirm the possibility that such monsters could occur in nature.