AIAndy: thanks, you put me on the right track for llamas and donkeys
Added Llama Migration - Active 90%, iWeight 50
on barren, scrub or desert tiles, starts at Scavenging, no feature, road, other bonus or improvement allowed on tile
Added Donkey Migration - Active 90%, iWeight 50
on plains tile, starts at Scavenging, no feature, road, other bonus or improvement allowed on tile
Added Walrus Migration - Active 90%, iWeight 50
on snow, permafrost or tundra tile, starts at Scavenging, no feature, road, other bonus or improvement allowed on tile
Added Seal Migration - Active 90%, iWeight 50
on snow, permafrost or tundra tile, starts at Scavenging, no feature, road, other bonus or improvement allowed on tile
Walrus and Seal may or may not work, my test cases don't get it to trigger, but show no error either, if you see them, let me know.
Removed a fire event that I had put in for testing
Added a few terrain types to the other game migration events - essentially mimicking the terrain type tag of the bonus infos - they still don't have all possible tiles available for this event, might change that.