Hugh of Fouilloy

His De avibus, a moral treatise on birds was incorporated into many versions of the popular medieval bestiary.

The author draws upon the Etymologiae of Isidore of Seville which assembled extracts of many books from classical antiquity that would have otherwise been lost, De natura rerum by Rabanus Maurus, Gregory's Moralia in Job, and Ambrose's Hexaemeron.

Hugh's prologue says that De Avibus was intended as "a teaching text for the lay brothers".

According to Badke's Medieval Bestiary, "at least 125 manuscript copies of the De avibus still exist, though some include only part of the text.

For the most part the text appears in manuscripts along with other theological works, often with some of Hugh's other books".