Thanks for your answer!
Pretty sure you can build pumps on constructed floor, which means you could drown them if you really wanted to,
I learned a lot about pumps & co in my last fortress, and I
could have drowned them, but for that I would have had to change significant parts of my fortress.
but in answer to your question, they'll never starve or die of thirst. Maybe die of old age, I don't know about that.
Thats what I thought, although DF is sometimes so detailed that I would not consider it outlandish if goblins would stop a fight to eat and drink, too.
Getting dwarves of lower archery skill to shoot through fortifications seems to require that you get them to stand right next to the fortification tile, although in my experience sometimes that still won't work. For future attempts there's no particular reason to do this with fortifications, put them in a 1-deep hole with no ramps. Since they're disarmed anyway it doesn't really matter, they can't flick their boogers or anything.
OK, my crossbow
mennoobs were probably not yet up to that level.
I already considered such a pit for that purpose, but dismissed it for the extra work, and for messing up with the layout of the fortress. Looks like I'll have to build a separate "fun room" for dealing with the goblins.
Do you know whether this is safe for those nasty rhesus macaques, too? They occupy quite some cages by now, and my attempt in stockpiling them into one cage was.... fun.
In the meantime I took care of the gobbos by digging a hole from the rear (difficult enough, as by the time the miner came, the squads have ambled off with the old complaint of "can't reach enemy"), but the g's headed straight for the exit, ending up in cages again...