 Bermudo was never honored with the title of count, although he was an important magnate and appears in charters signing as "dominus" (Latin for "lord") and also as "Vermudo Petriz Galleciae" ("Bermudo Pérez of Galicia").His presence in medieval documentation is first recorded on 1 April 1104 when, with his brother, Count Fernando Pérez de Traba, he made a donation to the Monastery de San Xoán de Caaveiro.He was a vassal of Queen Urraca of León and, with his brothers, swore his loyalty to her son Alfonso VII upon his ascension to the throne of the Kingdom of León in Zamora.