Stella vs Anhinga vs Owl

At least 3 times per day, an anhinga lands on the bulkhead. They drive Stella crazy because they don't fly away when she chases them. They know she can't reach them with the Invisible Fence (she gets within 8" & they don't budge). Then the barking starts. Besides the barking, the anhinga craps all over the bulkhead & it's disgusting.

Last night Stella & I went to Home Depot to buy some decoy owls to keep the anhingas off the bulkhead. When I installed the owls, Stella started barking at them, even though I brought them over to her to play with & smell. I think their spinning head freaks her out. First thing this morning, an anhinga landed right near the owl. Well that didn't work!

The next time it worked a little better.

But then, not only did the anhinga land right next to the owl, but he actually tried to knock it into the water with his wing! Now what should I do?