Like starlings, grackles have highly refractive black feathers when viewed in direct sunlight. These birds often travel in large flocks and roost in trees overnight. You learn quickly not to park your car under a tree that these birds spend the night in!
Grackles can clean out the seed from a bird feeder in no time. When our neighbors stopped putting out seed because flocks of these birds kept emptying their feeder, they started showing up at ours!