they are free-flying zoo birds which breed in the trees around the lake. They are fed at one end, but you can also watch them fishing throughout the day. I also saw a couple of black-headed ibis free-flying (I also saw them in 2006), and there's a marabou as well (I don't think he can fly though). The pelicans also appear to be free-flighted but I only saw a couple.
they're not fed by the public, so I don't think there's any danger of them taking an eye out (i.e. they aren't going to be getting all pokey and grabby like animals that are used to being fed)
I also saw a couple of black-headed ibis free-flying (I also saw them in 2006), and there's a marabou as well (I don't think he can fly though). The pelicans also appear to be free-flighted but I only saw a couple.