it happened to me in an old playthrough, so i don't remember what mods i had (SafeJobWorld i at least know for sure wasn't one of them)

it was very funny to use Areas to lock one male and one female birb separated from each other in laboratory holding cells, then unleash them whenever a trader (to sell their insta-babies) or a raid (to send their insta-babies to war) happened

i do remember though when i checked their 'Stats' that they had no Gestation Period and no Growth-to-Adulthood Period (or whatever it is) so as soon as Lovin' finished a fully grown UwU ready to f*ck was born

it was one of my funniest moments in this game when i suddenly realized there were over a thousand birbs on my map (mere moments after i first got the two birbs) but dear god did it also tank my fps. haven't played with UwUs since then but i love this mod nonetheless

Reminds me of that old Star Trek Original Series episode, "The Trouble With Tribbles".