A pigeon has landed on our balcony, and he won't leave. I think he might be sick. What should I do?

I’ve been trying not to scare him too much. I’ve closed the door now and turned out the light, but he’s still there.

Photo: http://yfrog.com/bc52tpj

He’s been out there for probably ten minutes now.

Edit: It’s probably worth mentioning that he’s not moved at all. He’s just sitting there looking around at things occasionally.