Later today I'm off to the Azores, again. And it was the recent news of breeding Killdeer, where two young were observed on Santa Maria, that prompted me to post this. Though debatable whether or not the Azores really is 'this side of the Atlantic', a breeding record of any Nearctic wader there is still pretty incredible... and it's presumably the first definite American species of wader to have had successful breeding confirmed (this year and last).
You may ask 'what about those Pec Sands in Scotland'? They bred successfully but how certain can you be of their Nearctic or Siberian origin?
White-rumped Sandpipers displaying in Arctic Norway? No chicks. And those Spotted Sandpipers that attempted to breed on the Isle of Skye were apparently unsuccessful.
So there we go, Killdeer is the only definite yank wader to have bred in Europe.