Mylar tape and slingshots
I've found that Mylar tape works real well. I had an old cassette tape that died, and I just pull some of it out and tie a few long streamers to shrouds, etc. I've seen it as party streamers in color. I had a cormorant that loved the top of my mast, and didn't know what to do. I live aboard, and of course human presence scared him off at first, but then he came back. I borrowed a wrist rocket slingshot from a friend and started firing mud clods at him. The hit the mast and disintigrated, but he didn't like it and eventually left for good. As a post script, Cormorant droppings dry to the consistancy of concrete almost on contact. Yech.