Its diet consists of acorns, corn, birdseed, nuts, suet, fruits, insects and, unfortunately, other birds' eggs and even their young if given the opportunity. It delights in teasing squirrels and scattering other birds from bird feeders. I once watched a squirrel trying to catch a blue jay. The jay allowed it to approach within a couple of inches, then flew up to another branch while the obviously frustrated squirrel attempted to catch up. Then, just as the squirrel was almost successful, in the last second, the jay hopped to a higher branch.
Many people dislike the wasteful habits of the blue jay.
One of the redeeming qualities of the blue jay is that it will warn other birds when a perceived predator is in the vicinity. It will call other blue jays and soon the human observer will notice several agitated jays bobbing up and down as they utter a chorus of warnings to every bird within earshot that there is a cat or raccoon on the prowl. As other species of birds recognize the warning calls of the jay, they frequently join them and mob the potential common enemy in an effort to drive it away. As blue jays are careless eaters, they drop bits of acorn cups with still-attached pieces of nut meats. Although blue jays are year-round residents in Canada, some do migrate southward in fall from the northern parts of their range.