This is from birdyologist:
The term "storm" came from old time hunters that hunted the west coast when they would get a huge storm (cold front) from the north it brought down these beautiful rare wigeon.
There are many common names for them: white cheeked, white faced, cream wigeon, but for the most people the name "storm" stuck with these gorgeous rare specimens.
Quickly to clear some things up a "storm wigeon" is not a subspecies or a really old prime adult. If so they would be just as common as the normal grey pepper cheeked American wigeon. They are actually an American wigeon that carries a rare recessive gene that is being expressed. They lack the pigment that gives wigeon the peppering in the cheeks. Instead the cheeks are a creamy to white, like the crown of the head and a vibrant green iridescent that looks really enhanced on these individuals from the eye to the nape and only certain individuals carry it.
Really fast the definition of just an American wigeon facial feathers which has grey background pigment on the normal pennaceous and dark to black pigment on the open pennaceous giving the face as a whole the grey background with black specks (peppering). There are a few color variants that carry the gene for example:
1.) Storm wigeon is lacking these pigments in both the open and normal pennaceous and so they have all white or cream cheek and neck feathers. 2.) Dirty storm or partial storm have white or cream pigments in the normal pennaceous but have dark pigments in the open pennaceous through the cheek and neck.
3.) Some individuals have white or cream pigments in the normal pennaceous but have dark pigments in the open pennaceous. This gives it a storm wigeon appearance. These are the most commonly seen that people think are storms.
These are the most common variation, but there are many individuals that have their own unique characteristics.
