Why is a moorhen’s bill (beak) red and not blue, green or purple?
According to some quick research I did on the subject, the red colour of the bill and frontal shield is actually linked to health – birds with brighter red shields tend to carry lower levels of bacteria and parasites. The colour may also help with asserting dominance, as individuals with more vivid red shields are more likely to win territorial disputes.
The yellow tip of the bill can also reveal information…