Swainson’s Hawks come in various shades of color, dark to light, as do most raptors. They can range from very dark to quite light, as is the individual below. Dark birds are called melanistic. Their feathers contain more than the usual amount of melanin pigments. This bird is simply pale, perhaps leucistic, a condition where pigment is less. That is more often seen in patches on a bird. Albinism is complete lack off pigmentation, a genetic condition. The photo of the bird in the tree shows the more usual plumage of an adult Swainson’s Hawk. The photos were taken recently in North Dakota. The light bird was being harassed by Common Grackles.