Ambient sounds are pretty fun to work with! When I designed sound for our production of Macbeth, our director wanted a stormy creepy outdoors type ambience for the witch scenes, so I found different thunder and wind samples, and sequenced it into a surround sound
track in Adobe Audition, then played it using 2 minidisc decks through four speakers to effectifly create four-channel surround sound. It was pretty cool having thunder comming from different locations in the
auditorium.
As for your case, you can find many CD's from Amazon and Borders and such that have ambient forest sounds on them, such as birds chirping,
etc... I'm sure you could find some on the internet as well, though I'd be very careful to find tracks that do not have much 'noise' on them because your objective here is to add to the performance, not to distract from it.
Ideally, for a surround sound environment, you'd probably want bird chipring comming from different locations, and I would do it by dumping your sounds onto a computer, then using a sequencing program such as Adobe Audition (or something like
Kristal audio engine which is free) to create two seperate tracks.. front and rear, then export those and record them to a pair of CDs and/or minidiscs to
play back at the same time with two minidisc or two cd decks
Baby crying and cow mooing sounds shouldn't be too difficult to find on the internet, If you've got a budget for sound, try
Sounddogs.com.
As for the giant's footsteps, you've got a few options. It ma be possible to find something on the internet, but most likely you'll end up either having to mic someone with a bucket of dirt and a hammer backstage, or you could record someone pounding something into dirt beforehand, then dump it into a computer and lower the
pitch, EQ & compress it,
etc.. digitally.
Have fun!