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How do jays and parrots produce blue and green feather colours without blue or green pigments?

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Animals communicate by sending and receiving signals. For example, a mother dingo (Canis lupus dingo) can communicate certain types of information to her pups by using tactile signals conveyed through grooming. — Animal communication Animals communicate by sending and receiving signals. For example, a mother dingo (*Canis lupus dingo*) can communicate certain types of information to her pups by using tactile signals conveyed through grooming.

Jays and parrots produce blue and green feather colours primarily through structural mechanisms rather than pigments.12

Blue Colouration

Blue colours in feathers are considered "structural colours". They are produced by a thin, porous layer of keratin that overlies a deposit of melanin pigment. This specialized structure reflects blue light, creating the appearance of blue plumage even though no blue pigment is present.123

Green Colouration

Most green colours in birds result from a combination of structural blue and yellow pigments. The structural blue produced by the keratin layer is modified by the addition of yellow pigments (such as carotenoids), which together create the perception of green.1

While most green plumage is achieved through this combination, it is worth noting that some rare exceptions exist, such as the African turacos, which possess a unique green pigment called turacoverdin. However, for the vast majority of birds like parrots, the green appearance is a result of the interaction between structural blue and yellow biochromes.412