Yeah Sammy, I heard about that too. There was a programme about that on a German TV channel I saw about a year or two ago. Apparently it's been illegal for years under Italy's own laws, but at the time of the above programme the EU were going to strengthen that rule. Don't know if it happened or not - apparently very difficult anyway because it's an "ancient tradition" in Italy (apparently these little birds are very good eating, can you believe?)! (And perhaps with only a LITTLE tongue in cheek, IME, yer average Italian ain't perhaps the most law-abiding of citizens)!
Re barn conversions and such, that MAY be a factor here, though generally speaking there's more new building going on than old house & barn, etc, renovations. Our local village council did put up a couple of nest boxes a few years back but from what I can see, they're empty this year.
So in the main, it's as I thought then, and in UK too, there's less of these lovely little birds about this year - so far anyway (and BTW, excuse my "bird recognition" - I MAY well be talking about House Martins as well as/instead of Swifts and Swallows - I see basically 2 different "types", one with a vee tail, one with a long straight rectangular tail).
No idea why this shortage.