The Sparra was a variation of Sparrows that lived in Redwall Abbey's rooftop as an organized tribe, monarchy and army. Sparras were extremely hostile, accomplished warriors, and their language was notoriously difficult to comprehend, though Matthias understood them extremely easily. They often referred to creatures and things as "Worms". Sparra warriors favored a popular gambling game called "Three Feathers". When a Sparra died, he or she was covered in leaves. The name of their habitat was Warbeak Loft.
As time went on, relations between the tribe and order of Redwall monks stayed the same, with neither encountering each other and staying out of each other's way, but the Abbey's war with Cluny the Scourge and, coupled with the death of the insanely-xenophobic King Bull Sparra and rise of the benevolent and wise Queen Warbeak, the tribe and Redwall united to defeat Cluny's rat army. Shortly after the final battle, the dying Abbot Mortimer ordered that the Sparras be allowed to come and go as they please, to which both sides agreed, and over the next 8 seasons, a new age of peace and prosperity befell the colony.
This ended when General Ironbeak invaded, killing the oldest, sickest, and youngest members of the tribe left behind during the mission to deliver information to Matthias (which resulted in the majority of the warrior's deaths, including Warbeak). The survivors later returned and rebuilt the colony, under the leadership of Sir Harry the Muse who, in an ironic twist, was not a Sparra, but an owl.
Since the events in Mattimeo, the Sparra have not reappeared in any books; when asked about this in an interview, Brian Jacques confirmed they continue to live in peace.