Kobolds die out for several reasons:
- short life span (to the point that we should actually bug it to Meph) means they do not marry/breed enough.
- wandering outside their sites and being eaten by almost everything (try to look into legends and see how historic kobolds die) due to small size
- being thieving race might not help.
- their sites are usually so poor they do not get attacked by anything.
We should perhaps consider modding their life span to a range of at least 30-40.
When I gen a new world kobolds are usually the first to go. Goblins sometimes manage to explode in numbers but they do loose every war they are a part of.
So, try to mod kobold maxage and gen the world again. Tell us how it goes.
Alright, I'm gonna science a bit then. I'm try first with a Maxage of 25-30, Then a Maxage of 40-50.
EDIT: Oh Yeah, even after only testing 2 100 year Medium region worlds, the difference is clear. Out of the 40 Civs, divided by 10 races, the 25-30 Maxage Kobolds managed to have multiple surviving civilizations. Their maxage is a factor clearly to why they tend to die out so fast. However, even with these, I am having kobold Civs that just seem to Vanish with no clear reason.
One Civ in the first generation had 4 Sites that were active, only to abandon all 4 of their sites and die off in the year 99. In the Legends viewer it says in Red above the maps "Last Known Sites Year 99".
Is it that kobolds do not breed enough during World gen? I mean, when you go into fort mode, its not uncommon to have 20-30 children/babies born by the 3rd year. Or is it like you said, that being a Thieving race might have something to do with this weird world gen quirk of mass site abandonment?