Well, RE: sounds available... I have a bunch of recordings I transferred from old 45rpm records that were part of a Varmint Calling system. You can hold onto "on offsite backup" copy for me
The one of the "Dying Crow" can literally make the sky go dark with Crows! And they'll even swoop down at ya all pissed off! And the "Domestic Rabbit" one I'd swear it sounds little a little girl screaming in bloody terror. These recordings are with old tech, so not the best audio resolution/clarity. But they're not bad though.
Also... as an example... with Audio Recording/Mastering software (I happen to use SOUND FORGE) you can record content streamed to you, such as from YouTube. Then chop-out the audio parts you wish to retain. Pump up the volume, apply some compression and so forth. I did a little of that with some of the vids from MFK calls and other sources.
And one of these days... if I get lucky... I'd like to try to record my "Lil' One" ( 5>Lbs Chihuahua) territorially barking at something in our backyard and use that out in the field! I feel certain that would drive the predators nuts!
I've also read that some people have used... successfully... as morbid as this sounds... the sound of a Human baby crying on a caller.
You would just have to make sure you're using a device that is OK with standard non-proprietary types of files such as MP3's. That Johnny Stewart GS2 I bought is cool like that, you can load in your own MP3's!
Most of the devices out there, for whatever reason, they have their own proprietary file formats and they're tight-lipped on the filespec, so there are no converters available for them since they serve such a narrow niche community of people.