Hmm... Are cardinals aggressive when it comes to their nests?
There's three cardinals out there right now. A male keeps chasing off an aggressive female who keeps trying to fly to the tree. The third is another female who brings stuff to her nest.
It makes me nervous. I have to go and change the hummingbird feeder tomorrow - I change it once a week. I wonder if cardinals nearby will chase the hummingbirds off. Oy.