At a distance, common grackles look like large blackbirds and sound like a rusty door hinge. But up close, their yellow eyes are rather expressive and their feathers have an almost peacock-like iridescence. Grackles, like northern flickers, allow ants to crawl on their feathers and secrete formic acid, which helps prevent parasites. Grackles may also use marigold flowers and walnut juice as bug repellants. Another interesting trait of these common birds is that, like pigeons and certain other birds, grackles have magnetite, a magnetic mineral, in their beak, which helps them navigate using the Earth’s magnetic field.