argh, stop going on about the birds, there are more sounds around IRL than birds noises, and those are missing too, the tyre sound needs some tweaking too; ///
I have never heard bees or birds over cars racing at any circuit ever, they are completely irrelevant to replays and TV cameras, if you want to listen to birdsongs then you can always load them in iTunes and leave them in the background.
Back to more relevant sounds, remember that LFS generates its own engine sounds, no other sim does this, you'll find that CRC will just be a load of sound files. When LFS is finished it will hopefully have surround sound. The Redline GTP mod doesn't have surround sound either but that still sounds better than anything else I have ever put through my speakers. The kind of ambient sound you'll here will be more cars and engines. I can tell you you're not going to stand a chance of hearing your pitcrew having a chat as you hurtle past them at 100 mph.
There is a need for better engine sounds and surround support but there is absolutley no need for ambient sounds like these. I have attached the starting sound from GTP which gives some idea to what you'll be hearing (although obviously not such a concentrated sound).