Cock fighting

“Thou lightest my lamp, O Lord: O my God enlighten my darkness…. Who teacheth my hands to war: and thou hast made my arms like a brazen bow.” Psalm 17:29, 35

Psalterium Cantuariense [Psautier de Canterbury] Source: gallica.bnf.fr
Bibliothèque nationale de France. Département des Manuscrits. Latin 8846, fol. 27v.

Why is there a rooster on a post? Compare with the Utrecht Psalter: http://psalter.library.uu.nl/page?p=24&res=5&x=1447&y=4148