“Just get past them, I think,” said Charlie. “We'll be on hand if it gets nasty, Extinguishing Spells at the ready. They wanted nesting mothers, I don't know why…but I tell you this, I don't envy the one who gets the Horntail. Vicious thing. Its back end's as dangerous as its front, look.”
I couldn't find any reference about "nesting mothers" anywhere. What does it mean?