Sircolo was a marsh harrier, a vicious bird of prey who dwelt in a marshland just outside Mossflower Woods. According to Swiffo, Sircolo ate just about anything that moved, only sparing those who were personal friends of his.
When the Fortunate Freepaws were fleeing from Razzid Wearat and his crew, they passed through Sircolo's territory. The big bird challenged them at first, threatening to eat them, until he realized his friends Rekaby and Swiffo were with the band. He then granted them passage, showing them the way out of the swamp.
Later, he returned to the marsh and slew Razzid's tracker Ricker, carrying the rat off to eat him.
- Sircolo's name is probably derived from circus, the scientific classification name for marsh harriers.
- Sircolo is the only harrier to ever appear in the Redwall series.