What special relationship does this bird have with ants?
This is a Common Grackle. Grackles are one of several species of birds that have a behavior called "anting". They pick up ants, and rub the irritated insects against their feathers. This releases formic acid, which helps remove mites and other small parasites from their feathers. Sometimes, instead of capturing an ant, the bird will sit on an ant nest to get their dose of formic acid.