Bird Opening with 1...f5

1...f5 is dubious because of the Gambit by White, 1.f4 f5?! 2.e4! fxe4 3.d3 with advantage.

The extra tempo, 1.f4, is extremely useful here.

There was even an old book for Black in the 90's - Play the Dutch Against 1.c4 and 1.Nf3.  It actually mentions that the Dutch, 1...f5, is playable against 16 of White's 20 legal moves.

The 4 where it is bad?

1.e4 - Obviously

1.g4 - Obviously

1.Nc3 because 1...f5 2.e4! Is very strong for White

1.f4 because 1...f5 2.e4 fxe4 3.d3 exd3 4.Bzd3 is advantage White.

I specifically play 1...f5 only against 1.c4, 1.Nf3, and 1.g3.  Against 1.d4, I play 1...e6, and if 2.c4 or 2.Nf3 or 2.g3, I play 2...f5.  If 2.e4, I play 2...d5.

It avoids 1.d4 f5 2.e4, 1.d4 f5 2.Bg5, and 1.d4 f5 2.Nc3.  After 1.d4 e6, 2.Bg5 loses for White, 2.e4 d5 is the French, and 2.Nc3 d5 is fine for Black.

Bent Larsen didn't play it as black. 

1...f5 avoids an imbalanced game, which is hypothetically a main reason for playing the Bird's opening.

I'm aware of the e4 gambit. I believe the main line goes like this: