This, I'm afraid, is utterly depressing and terrifying in equal measure. I'm used, like any other birdwatcher, to reading about worrying declines in all sorts of species. Turtle Dove is one which has been much talked about (although to very little effect), and then there are the likes of Willow Tit, and Curlew. The former has disappeared from large parts of the UK, as has Willow Tit (with some small glimmers of hope in old industrial areas), while the speed of the latter's decline is alarming.
But the species being talked about here are absolutely everyday birds. Rook, for heaven's sake. Swift. If they too are starting to shrink back into ever-smaller breeding areas, where they raise ever-smaller numbers of young, then it's hard to avoid the conclusion that we have broken the natural world beyond repair.