They apparently resemble horned birds, and are used to low gravity enviroments.
they are intelligent and friendly toward aliens. They believe in cooperation and communal life and ownership of property, goods and services. They resent competition and exploitation as violent and evil; as a result they favor restructuring the economy of other Known Space worlds to match their own.
Their religion is animistic and relevant to every aspect in their daily life.
Pierin are also famous poets and musicians and also pilots, with unique skill and ability in acrobatics. 
The Pierin had colonized several planets around p Eridani.
They might likely have been liberated by the Humans with the end of the Man-Kzin War.