Since the creation of life is never an exact and uniform process, we can see a lot of big differences in how people can turn out.
As you expect, the same is true in nature as the way that genetic materials mash together to create a new animal is just as unpredictable as it is for us.
But while certain mutations can certainly be rare in our world, it's easy for them to become even rarer in the animal kingdom. After all, many animals end up with the colors they do for a reason and a green animal will definitely have an easier time hiding among the brush than a white one.
Nonetheless, some animals with this disadvantage can still find themselves surviving long enough to amaze and fascinate us and one particular bird doesn't seem to be letting anything slow it down.