Question About Hawk Repeller Ideas

It was a beautiful sunny morning and when I looked out at the pond, there were 15 or 20 Robins hanging around, drinking water and bathing. So the questions is: Do the moving shining strips scare a 2 foot tall Hawk with a 5 foot wing span and not scare an 8 inch tall Robin with a wing span of less than a foot? I haven't see the Hawk but inquiring minds want to know. I picked out a bunch of leaves and some string alge this afternoon. The string alge seems to be a lot worse this year, maybe because the winter has been so much warmer than last year. I did see a bunch of fish laying near the bottom even though the water temp is about 48 degrees.