Discussion of level 4 monsters.

Why not? A beak attack hurts anyone, but there won't be a lightning strike on birds. They have immunity.
What do you mean? There's nothing in the game related to "lightning strikes."

I didn't notice any immunity in birds – they often mutually attacked each other with lightning. There's no limit to the chance of lightning strikes in the descriptions, but I remember that sometimes it didn't happen. Perhaps this happened in a battle between a bird and a Barbarian, who has partial magic immunity, or in some other situations (luck, ward, etc.), but it might not be a 100% chance. I'll try to test it when I have time to clarify.
xTrishax
CD, MD - king-dragon, mega-dragon - this is a dragon that has eaten so much that it can't fly or fit into any dwelling, so it lives wherever it can.