According to Eglor in Ravens vs. Eagles, the tribe is a utopian collective where no one owns anything and everything is shared. Razar says they dont believe in shopping, though Eris says they still buy thing at the Chi day market. In the same episode, Eris says the "who goes where" rules are governed by common sense. They also appear to have the ability of calling other tribes like the Lions do, as shown in the finale of season 3. It also could be that only royal/council Eagles can do this, like with the Lions, since Eris was the only one to use this ability. The calling noise is a shriek.