With Habsburg Monarchy (Livestock Colony) Level 5 (Wave of Immigration), do you do the effect before or after the Explore on that turn?

With Habsburg Monarchy (Livestock Colony) Level 5 (Wave of Immigration), do you do the effect before or after the Explore on that turn?

After completely resolving the Explore Card above it, but before resolving the Adversary's "After the Explore Step" Escalation. If you're resolving another Explore Card that turn, e.g., because you're playing the Surges of Colonization scenario, resolve the effects of the Reminder Card before revealing the next Explore Card. Similarly, the effects of the Reminder Card happen before anything triggered by Advancing the Invader Cards, like the extra Build Step caused by the "Fortification" Event.
Formally, Reminder Cards resolve once you're done resolving the Invader Card above them. (Or, in unusual cases like this FAQ, if they end up atop the Invader Deck.)
This ruling originally implied that the "Seek Prime Territory" Escalation happens first. Because the timing of the Escalation was made more explicit in later printings, this ruling has been updated accordingly.