Leucistic And Albino Birds
Leucism in birds is caused by a lack of melanin, a pigment responsible for black, grey and some browns. A leucistic bird will have white feathers unless its normal plumage also contains carotenoids which are responsible for yellows, and which are unaffected by the condition. They can often have normal coloured eyes, bills, legs and feet.
Leucism is inherited but the extent of the condition can vary between adults and their offspring and it can also skip generations if the leucistic genes are recessive.
Leucistic birds will have weakened feathers, which are more susceptible to wear and tear, and, as a result, they may have difficultly flying. If they have very large patches of leucism, they are going to be more conspicuous and vulnerable to predators. In some cases a leucistic bird may not be recognized by a potential mate.
Some birds suffer from a similar condition called dilution in which the plumage colour appears “washed out”. Melanin cells are present but they produce less pigment than normal.
True albinism is a much rarer condition and is caused by a genetic mutation which causes a complete absence of tyrosinase which means no melanin pigments can be produced at all. A true albino bird will always have pink eyes because the only colour comes from the blood vessels in their eyes.
Most albino birds born in the wild will die shortly after fledging due their poor eyesight and it is not thought that any wild albino birds have survived to adulthood.
As with leucistic birds, some albino birds can have carotenoid pigments so they have some patches of colour on their plumage. However, it is incorrect to describe these birds as ‘partial albinos’ as albinism affects the whole plumage of the bird.