What is the best move after F4 in the bird's opening? (as white)

I am quite confused about this.  I did not know what the best move was here,  I wanted more information,

so I thought somebody would know the best move.

Hello?

After white plays 1. f4, the first question is what should black play? There is plenty of room for disagreement. Each of the following moves are playable: d5, c5, Nf6, g6, d6 and the provocative gambit e5.

Now back to the main question - what does white do on move 2 and beyond? White can choose from at least three major setups against most black moves. First, white can combine the Bird's Opening with Larsen's Opening. His next moves are most likely b3, Bb2 and Nf3. Second, white may choose the Stonewall Attack. Now he would continue with Nf3, e3, d4 and Bd3. Finally, there is the Fianchetto or Leningrad system. White quickly plays Nf3, g3 and Bg2.

Alas, the From's gambit 1. f4 e5 requires more careful treatment. If you prefer sacrificing a pawn instead of accepting a gambit, then e4 transposes into the King's gambit. However, real Bird players will grab both the e5 and d6 pawns, then develop with Nf3.

Good luck!

There's no best move?

Also there's that opening where white plays f4 and c4.

obviously a6

The Bird is like the Dutch defense... For white. So learn how to answer to the Fromm Gambit: 1.f4 e5 2.fxe5 d6 3.exd6 Bxd6 and if white does nothing black can checkmate the black king, by Qh4+ g3 Qxg3+ Bxg3#! So as it has been said, play 4.Nf3. Then your opponent will have the choice between g5 and Nf6. I know someone that plays a very interesting variation with the mobe 5.c3 after 4...g5. I don't remember well this variation, but try to explore it on a computer. 

Secondly learn how to transpose to your favorite line of the Dutch if your opponent plays d5. If you like the Stonewall, play e3 and d4. If you like the Leningrad, fianchetto your f1 Bishop, etc. 

That make's sense...

I knew Mike would be all over this :-)

On 1.f4, if black doesn't play ...e5 you play 1.Nf3. 

There are other cases not to play 2.Nf3.  For example, I even have a game on ICCF going on where my opponent played 1...b5.  1.f4 b5 should be first answered with 2.e4 Bb7 3.d3 and then 4.Nf3, 5.g3, 6.Bg2, 7.O-O, and then expand kingside.

Black has also tried a Kingside Benko with 1.f4 g5 and White should take in this case.

Against the "Sicilian", I play 2.Nf3, 3.e4, and 4.Be2, but White can also do 2.e4 and play a Grand Prix Attack.

So 2.Nf3 is not automatic against Non-1...e5.

Nobody plays Bird opening, braw. Not seriously. If a super GM don't play, a patzer don't play.

You have no clue what you are talking about lowly 1600 player.

We have 3 titled players right now playing in 2020's 4th thematic (of 7) at the ICCF.  What is that thematic?  Bird's Opening!  1.f4, Black to move in every game.

My own high school club's ace (who was about 2000 rated by senior year) played Bird's Opening exclusively, and to excellent effect.  Beat a GM with it.  It forces black into dynamic play, which is uncomfortable for many.

Exception to the rule... I asked for a super GM who plays the Bird. Not some patzers nobody ever heard of.

You want a Super GM?  Lasker beat the snot out of Bauer!  He was only a world champion!

Yeah. Did they have railroads back then.

Invention of the railroad: 1830

Lasker blows away Bauer with 1.f4: 1889

Railroad was 59 years old.  What next Mr IKnowNothing?

Hmm. I guess that proves I'm nobody.