Kate was surveying the cove when she saw an intruder.
It was another fully mature female bald eagle. One I did not recognize.
Instantly Kate was out of the nest and above the other female.
Kate stayed in the higher position, talons dangling in a threat posture.
She herded the other female out of the cove. Both eagles were screaming.
When Kate got the intruder far enough out over the main lake, she turned and bolted for the nest.
Mom mission accomplished.

to see a short slide show of the interaction, please go to https://flic.kr/p/EKGqCA