Sometimes, genetics likes to throw a bit of a curveball when it comes to coloration of animals. These quirks can tip the scales in favor of all white or all black fur, feathers, or even skin and can even land somewhere in the middle in a genetic condition known as leucism.
Recently, the North Island Wildlife Recovery Centre in British Columbia, Canada, shared on social media about the death of their beloved leucistic raven called Blizzard. This is not the only place in North America to see white ravens, as in Anchorage on the Kenai Peninsula, USA, a white raven was seen in winter 2023 and 2024, and was even filmed by a local.
While leucism is a pretty rare occurrence, it does have some tell tale signs. Unlike albinism, leucism does not affect the eyes but instead can result in patchy (known as particle leucism) or a completely white appearance (known as total leucism). Both conditions are caused by a lack of the substance melanin that normally produces the typical coloration of the feathers; therefore, a lack of this substance can make the feathers appear white. There is some debate as to whether leucism is genetic or occurs during development of the embryo.
Unfortunately, both albinism and leucism can come with additional health issues. As well as not being of typical coloration, which can cause an increased risk of predation to some species or result in social ostracization in some cases, these conditions can be coupled with skin and eye problems.
In some species, feathers play an important role in impressing a mate, meaning individuals with feathers not in the typical coloration may struggle with finding a mate. It is even suggested that feathers with less pigment are less robust and can wear down more rapidly impacting flight and the ability to maintain body temperature.
There are also other types of pigment changes, including melanism, where the animal appears blacker, due to more melanin pigment being present; erythrism, where an animal appears chestnut or bronze instead of their typical colors; or xanthochromism, where there is an excess of yellow pigment often instead of red.
Source Link: White Raven: This Normally Black Bird Can Be Surprisingly Pale