How can you distinguish Berserkers from other Uruks?

I have just begun encountering Berserkers. They are enemies who can counter normal attacks, so you have to stun them before attacking them. If someone counters my attack, I can tell he's a Berserker that way, but that involves me taking damage from his counter.

Is there a way to tell an enemy is a Berserker before I attack him, so I can avoid this trial and error method of combat?

They have two weapons. From the wiki:

Berserkers - Similar to warriors, but wield two weapons instead of one. Deals much more damage and are capable of throwing their weapons. Cannot be attacked freely since they counter the attack, must be Wraith Stunned before any attacks can land on them.