How do red factor canaries turn red?

Red factor canaries turn red due to a mutation in the cytochrome P450 enzyme, which is responsible for the metabolism of certain pigments in the body. In red factor canaries, this mutation leads to an accumulation of the pigment psittacin, which gives the bird its red coloration. Interestingly, this mutation is sex-linked, meaning it is carried on the X chromosome, and as a result, it is typically expressed only in male canaries. Male canaries with two copies of the red factor gene (one inherited from each parent) are known as "double red factor" and exhibit the most intense red coloration. Female canaries, on the other hand, typically have only one copy of the red factor gene and are not as brightly colored as males, often appearing more orange in hue.