Leucism in Bald Eagles
You have probably never heard of the condition leucism, but you likely have heard of its close cousin, albinism. An albino animal has a rare genetic mutation which prevents its skin from producing melanin. This deficiency results in a paleness and lack of coloring on skin, hair, and feathers.
Leucism is another genetic condition which is very closely related to albinism. Leucism causes an absence of all skin pigments, not just melanin. Leucism is caused by a mutation in the c-kit, mitf, or EDNRB genes. Just like albinism, the effect of leucism is to drain all color from a creature. Oddly enough, leucism will not affect yellow hues.
The condition can appear in many sorts of animals, including birds, fish, and reptiles. In birds, leucism can manifest either partially or completely. A completely leucistic bald eagle would have pure white plumage. An eagle with partial leucism can be described as pied or piebald, and has patches of white coloring.
I have been lucky enough to photograph the leucistic bald eagle for several years. I first spotted this unique bird while photographing bald eagles in 2010 on the Chilkoot River in Alaska. This Bald Eagle quickly gained the nickname “White Tips,” for the unique white-tipped wings it exhibits. In 2011, I returned to photograph this special eagle this time on the Chikat River, just North of Haines, Alaska. The piebald patterning on this eagle allows us to easily identify it. Luckily, White Tips must enjoy the salmon fishing along the Chilkoot and Chilkat Rivers.
White Tips only has partial leucism, making it a pied eagle, or a piebald eagle. White Tips has a very unique patterning due to his leucism: white wing tips and white talons. There are five white feathers on the tip of each wing. White Tips’ talons are completely white, not black as is normal for bald eagle talons.
The leucistic Bald Eagle was a joy to photograph. The piebald eagle’s white-tipped wings really shine while it is in flight similar to a magpie in flight, as the individual coloring accents the flapping of the wings in a very special way.
Although it can be beautiful, leucism can cause health problems for birds possessing the condition. The color pigments that are absent from White Tips’ wing feathers usually help add strength to the bird’s wings. Without these pigments, a leucistic bird will tire more quickly.