Build a webpage with a flock of birds flying endlessly around on it

I would like to build a webpage with a flock of birds flying around on it. White background, black, "bird-shapes" to begin with - I'm thinking folding triangles. Eventually I would be interested to generate random flying patterns but for now I would be happy to make regular, repeating patterns, with one "bird" to begin.

I'm wondering how might this best be achieved or where to begin? I have plenty of programming experience with Java, and some in HTML/JavaScript. But I'm interested to learn. I'm just looking for a few pointers. WebGL? Or just use JavaScript?