One of the easiest ways to help swifts is to keep your eyes open.
Between May and early September, is scaffolding being put up in your neighborhood? Possibly even covered with nets?
Young swifts could be being condemned to death right now!
Observe whether parent birds are desperately trying to fly to their nest - blocked by scaffolding and netting - to feed their young! If so, immediate intervention is required. First and foremost, speak calmly and politely to the construction workers and ask them to remove the nets at the roof eaves. Often this alone is enough to allow access again. However, walkway boards may also need to be removed if they are obstructing entry.
If your request is rejected, contact the Lower Nature Conservation Authority. Insist that staff members go to the site immediately to assess the situation and initiate measures.
But it does not have to be so dramatic. Perhaps you will simply find an ideal place to create a nesting site.