If my memory is right, Mariah got more aggressive every year than the year before.
That's my memory as well. I recall one of the bird behavior experts on the board speculating that perhaps Mariah learned that her behavior had the desired effect, so it caused her to do even more of the same behavior the following year. In other words, somebody took her babies, which she reacted to with aggressive behavior and warning cries. The babies were returned, therefore, the aggression and warning must have intimated the evildoers. So the next year...even more aggressive!
Patti