[He returns that smile by making his own a little bigger, which stays even as he surveys the roof, trying to get a feel for what's so special about this one. Steven's theories earn a short, quiet laugh from Atreus.]

Birds don't really care about that. They're more focused on safety and access to food. So... Maybe this place has a lot of food nearby, and predators can't get to them?

[But this is a pretty open roof...]