When the monarch becomes a butterfly, it no longer eats milkweed, but it still has the chemical in its body. The butterfly shows that they are not good to eat with their bright orange and black wings. This is warning coloration. A bird may try to eat a monarch, but it will become sick and vomit after eating it. After this experience, the bird learns not to eat another monarch, and also any other butterfly which is similar in appearance. The viceroy is similar looking to the monarch, but does not have the milkweed poison in its body. Birds that have had the bad experience of eating a monarch will usually not eat a viceroy. It is an example of Müllerian mimicry.