Sexual selection and social selection are two important theories proposed for explainingthe evolution of colorful ornamental traits in animals. Understanding signal honestyrequires studying how environmental and physiological factors duringdevelopment influence the showy nature of sexual and social ornaments. We experimentallymanipulated physiological stress and immunity status during the molt in adultking penguins (Aptenodytes patagonicus), and studied the consequences of our treatmentson colourful ornaments (yellow-orange and UV beak spots and yellow-orangeauricular feather patches) known to be used in sexual and social contexts in this species.Whereas some ornamental features showed strong condition-dependence(yellow auricular feather chroma, yellow and UV chroma of the beak), others werecondition-independent and remained highly correlated before and after the molt (auricularpatch size and beak UV hue). Our study provides a rare examination of the linksbetween ornament determinism and selection processes in the wild. We highlight thecoexistence of ornaments costly to produce that may be honest signals used in matechoice, and ornaments for which honesty may be enforced by social mediation or relyon genetic constraints.