I don't think the birds have any effect on performance, but I would like an option to turn the encounters down or off completely. I feel they show up a bit too frequently.
On the topic of Labyrinth; I don't have the best computer, but with my settings on the lower end I can usually pull at around ~25 fps. However, on labyrinth i literally get 5 fps. The whole time. The latency seems to be fine, and I don't really notice any lag spikes. It's the frames that are a problem with me.