(covers information from several alternate timelines)
These two unnamed Klingon Birds of Prey help Dura's ship by launching a third attack on the Enterprise NX-01, captained by Jonathan Archer, which was preparing to go into the Delphic Expanse. This time, Enterprise managed to evade the attack by entering the Expanse, something which Duras was willing to risk, but the other ship captains were not. The two Klingon Birds of Prey reluctantly withdraw while Duras continued his attack on the Enterprise. It is unknown where these two ships went. It is probably likely they went back to Klingon territory. (ENT: "The Expanse").
These two Klingon Birds of Prey escorted Admiral Krell's D-5 class battlecruiser and took part in the attack on the Qu'Vat Colony. (ENT: "Divergence").