Recently in Dwarf Fortress (0.47.03), Fortress Mode, I had one of my usual migrant waves. However, instead of the usual "migrant wave" message:
Some migrants have arrived.
The message this time was:
Some migrants have arrived, despite the danger.
This is strange to me, because my fortress is in a fairly remote location and has never been under siege, or attacked by werebeasts or other monsters (yet). There have been some deaths, obviously, because you can't have a fortress without random deaths happening - a dwarf was killed by a capybara last season, and some dwarven children starved to death when I accidentally forgot to turn off the panic burrow - but overall the fortress is very peaceful, so seeing this message surprises me.
According to this forum post, this message might be a result of your fortress having an unusually high death rate, but I can't find any source confirmation on that besides Reddit and forum messages, and my fortress hasn't had that many dwarves die. I've also seen forum speculation that this message means there are spies, ambushers, or other enemies on the fortress property, but I've scanned and scouted the place thoroughly with my military dwarves and have not found any enemies hiding anywhere.
Why does this altered migrant message appear, and what does it mean?