Associations between colour parameters
At the individual level, yellow UV chroma of nestlings was positively
correlated with yellow brightness (r = 0.34; P <
0.001; n = 1834), and negatively with carotenoid chroma (r = -
0.54; P < 0.001; n = 1835). In contrast, there was no
relationship between carotenoid chroma and brightness (r = -
0.010; P = 0.70; n = 1834).
When running the correlations of colour parameters at the nest level,
mean yellow UV chroma was positively correlated with mean yellow
brightness (r = 0.54; P < 0.001; n = 234; Figure
1a), and negatively with carotenoid chroma (r = -0.52; P< 0.001; n = 234; Fig. 1b). Moreover, the relationship between
carotenoid chroma and brightness was slightly significant and negative
(r = -0.14; P = 0.030; n = 234; Fig. 1c).