Bird was one of my favorite openings, in the days when I was playing regularly. But I do not recall ever seeing this particular variation, with White very aggressively laying his king-side completely open... Interesting game, I will study this some more.
Here is my analysis of the moves in question, for what it's worth. I have not done this for a long time and do not have a board at hand, so I will probably say something stupid or get my move lists wrong, but here goes.
I have to conclude that White simply missed 18. Ne6+. It was a blunder pure and simple. Whatever way you look at it, White would have won with that move. 18. ... Kc8 loses to 19. Qe8+ Qd8 20. Qxd8#; and 18. ... Kd7 loses to 19. Nf6+ Kc8 (the e7 pawn is pinned) 20. Qe8+ Qd8 21. Qxd8#.
I initially thought that White may have missed this due to time pressure. But Max rightly pointed out that they have only played 18 moves at this point. Unlikely that White would have been running short on time, but who knows.
I think it is more probable that White was temporarily blinded by the triple fork on f7 (against Black's king, queen and rook). Effectively, White's move effectively forces 18. ... Ke8 so as to save the Black queen.
Black resigns because after 19. ... cxd5 20. Nxh8 he down a rook for a knight, and the only way to "unhang" the knight on f3 is 20. ... d4, but that allows white to play 21. Qd7+ (again!) this time winning the bishop. So either way White is a full rook up and should go on to win.
The mate would have been prettier though :)
I had a couple of opponents play 1. f4 against me recently, so decided to look up some game examples. I've got mco, but havent had a chance yet so looked up on an internet database. i came across this game straight away, and my question is to do with the end of it. It is apparently played between two strong players and I havent spent too much time on it, but I dont understand why white didnt win by 18. Ne6+, then in the final position why black resigns. This sort of thing annoys me because I am either inadequate (probably) or the GM missed something I 'saw' straight away. Comments appreciated.