Two birds stand back to back on each side; their heads nestle against each other in the corners. Their bodies and wings form two opposing diagonals; their tails are intertwined in the corners. The motif is developed in an extremely decorative and utterly symmetrical way. The bodies of the birds with their very flat wings are not sharply raised in relief from the markedly round-bellied calathos.
The frieze of the impost block is adorned on each side with a row of birds placed in medallions formed by paired tendrils which sprout blossoms from the knots that tie them together. This motif is derived from an impost in the north transept of Saint-Sernin in Toulouse, where it was also taken over in more or less identical form by Bernard Gilduin in the table-altar.