Well it's just good that the parasite cannot control complex organisms, for example, it cannot control the bird. It can only take control of something simple like a snail. For now.... until it mutates.... and we become disgusting worm breeding vessels that vomit on other humans to infect them with more worms...
Oh wow that's really impressive, parasites hijacking other organisms really freaks me out. Just like the one which makes sticklebacks swim near the surface so herons can eat the fish, so they can get into a heron.
Reminds me of the spores which get into insects and kill them, then grow out of their heads. Seriously scary. Found it...