It's a fantasy role-playing game.

DM: You are Vex Vex'ahlia, a half-elf ranger . You are the member of the famous group of adventurers. Previously, Ogden tells her the history of how the Trickfoots were first cursed. He explains that he has spent his life researching this curse, and once succeeded in exorcising it from Johann some years ago.
DM: Okay. You do note this in the first couple days: while it's been long blown-over and destroyed and scattered, you do see elements that seem like a large nest that have been wind-scattered up here and left for a long time. And as you look through the chunks and pieces, you see bits of dried leather, flesh, and with that in mind, over the next two days, you begin to see, way off in the north, what appear to be a number of flying entities that group in clusters that kind of exist over the cliffside, down along the actual mountain edge, and occasionally have apparently made distant nests and are still maneuvering in the distance.
Player: Do I see the type of feather it is? Can I tell what kind of creature it was?
DM: Make a perception check.
Player: 32.
DM: Using the combination of your broom and your ranger-like vision, you've encountered these creatures once before, at the Salted Bluff, but avoided them. There are small clusters of harpies that make their home here on the cliffsides by the ocean.
Player: Yeah, they took all our horses.
DM: Yep. They picked them apart last time you first made your way to Whitestone. So you're very careful to make sure that whatever camp you set up is camouflaged as best as possible. Since that is one of your specialties as a ranger, it's not too bad. Go ahead and make a stealth check, please. This will be your stealth check for the camp.
Player: I can't cast Pass Without a Trace?
DM: Not on your camp.
