Statistical models describing seasonal chromatic changes (ΔS) over the year.

Significant variables are depicted in bold. For the two studied patches where there was a significant sex*month or sex*month2 interaction males and females were analysed separately (sex*month2, bill blackbirds F1,120.5 = 5.9, p = 0.016; back blackbirds, F1,115.9 = 7.02, p = 0.0092; all others p>0.06).
*analysis carried out on Box-Cox transformed variables to improve normality of residuals. Note that here effect sizes cannot be directly compared with those of untransformed variables.