down here in sacramento, we don't have blue jays, we have something similar, i think its called a sterling jay or somewhat close to that name. they look just like a blue jay except for they have a black face that fades to the navy blue body with a greyish under belly. yes they are agressive also. i had have seen them come down and peck the brains out of little chicks and thats all they eat of it. usually there would be four to five of them. they would perch in the trees and two of them would come down and pounce on the chicks. if you were to step outside thinking that those were the only two, you are wrong. the rest up in the trees would squawk bloody murder and the two on the ground would fly off. they often raid robin nests and sparrow nests. their main competitors are magpies. i see them fight sometime for territory and the mags always end up winning but not without a fight from the masked bandits. when my brothers and i were younger, they were considered trophy games because of there alertness due to their hunting strategy. so if you could sneak and pick of a few, you were the grand sniper.