As Bird Jaguar was not the son of Lady Xook (Itzamnaaj Bʼahlam's first wife-aunt), he was not completely of the royal blood and would have difficulty acquiring the throne.

A contemporaneous inscription from Piedras Negras mentions a ruler named Sak Jukub Yopaat B'ahlam being in office in July 749.

[1] On that day, Sak Jukub Yopaat B'ahlam witnessed the anniversary of Piedras Negras Ruler 4's accession.

Either Sak Jukub erected no monuments, or they were destroyed by Yaxun B'ahlam, as he is only mentioned one time at Piedras Negras.

[3] In order to legitimize his claim to the throne, Yaxun Bʼahlam had a series of stelae created that pictured him with his father (including Stele 11).