It's been wet here too. Last year was extremely warm over here in Austria (multiple temp records broken), and the slugs stayed near the small (mostly dry) creek that runs along the border of our small plot. There's a small concrete tunnel running below the train rails behind our house, and it was filled to the brim with slugs.
This year is much wetter, and our plot is slowly starting to get resuscitated. But as there is no balance as of yet, the army of darkness is performing a successful blitzkrieg. I say this with great interest, and not frustration or anything. Predators will eventually show up, I expect.
So, ducks don't eat young vegetables the way chickens do? My friends who keep a couple of dozen chickens and three ducks have built an elaborate fence around a huge expanse of lilac bushes because the chickens were eating their spring veggies. The lilacs keep them from getting a run at the fence, so they can't fly over it.
That's our plan for next year. The ducks will form a barrier between the creek (where I believe most of the slugs come from) and our garden zone, which is slightly elevated compared to duck domain. Behind the house is where the chicken will have around 600 square metres of room. We're going to try and take meat-producing breed, as these get bigger and have a tougher time flying over fences (and still produce plenty of eggs for our needs).
So, the upshot is, why are you so sure the ducks will take care of the slugs? We've always heard that beer will attract and drown slugs. You embed a can in the earth and fill it with beer. I have not tried this myself. I don't grow lettuce, which I suspect encourages slugs.
I'm not sure the ducks will completely take care of the slugs, but they should decimate their numbers significantly. 2 years ago when I was fooling around with my first garden behind the place we rented, we had a slug problem as well. I would get up early every morning and collect them in a small bucket. After 2-3 days I would take the bucket over to my neighbour who had around 10 ducks.
The ducks ran away from me at first, until they understood what was in the bucket. They then came running to me.
We tried the beer trap yesterday and the day before. It works. But you have to combine it with other stuff, or else you'll just attract more slugs to your seedlings. We're thinking about buying
this thing, a tiny copper fence, but I'd rather do without.
Like Ghoti says, planting a lot of extra stuff, so it doesn't matter if the slugs get some of it. That's what we'll also do next year. Or let the seedlings get really big before transplanting.