Are SIC and SkyTEST incompatible? Where did you get that info?
It's already "compatible" in the sense that it won't crash your game or cause any major issues.
Like any mod which edits vanilla leveled lists you need to use Wrye Bash to create a bashed patch in order to get all the changes to those lists from both mods (in this case, changes to lists with animals).
Without a bashed patch you'd only see the changes from whichever mod loads later in your load order.
With a bashed patch and the current version of SIC you see both the new SIC animals and the new SkyTEST animals. However, the SIC animals won't have SkyTEST behaviour, and faction alignment may be slightly off.
Factions etc. haven't been aligned in the current version for optimum compatibility. The upcoming version will use SkyTEST faction and AI settings for the SIC animals.