mockingbirds and not sure about the blue jays
@westie :
Mocking Birds and Blue Jays are the two most "territorial" small(song) birds in SE Texas(maybe all of TX, I dunno)....They will chase away anything in their "territory" once they've established that area....Mocking Birds are probably the worst....It's not uncommon to see them swooping down and pecking on the back of a cat just passing by....They even do it to humans, coming within inches of their heads and sometimes even pecking it....
I've never understood how the USELESS "Mocking Bird" is the "State Bird" of FIVE states....Not only is it territorially aggressive but it's also extremely ANNOYING when it sings/mocks all the other bird's songs late at night and through the early morning, especially if it's perched not far from your bedroom window!....
And if you've got a backyard "bird feeder" like me and enjoy watching a variety of birds stopping by like I do, I'm sure you can't stand when a Mocking Bird or Blue Jay comes in and runs all the other birds away!....