Heine (1982) noted in Kibera su ras for 'hair' and su téri for 'feather'.
So, ris means 'feather' alone, while su in association with another word means 'feather' (su téri) or 'hair' (su ras) (but not 'body hair', 'head hair').
Source: Luffin 2004: 88
Source: Heine 1982: 75
Source: Heine 1982: 74