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

Hate on football all you like, but I will brook no bashing of strippers dancing about.

We need more stripper!

?

SNUDOO knows the birds opening really well. I've seen him play it quite often. I would recommend you learn from his games. 

e3!!!

if black prevents e4 with moves such as d5 or Nf6, e3 is best. If black plays something else such as Nc6 or d6, e3 is a good choice followed by Nf3, Bc4, and O-O.

2.. e5! win for black

Win for white.  

i have to defend from the white side, whether I want to or not.

Thanks!  I feel honored.

Stonewall

na. If both players choses the same struckture, i name it middle tubee system it is vere drawish

1.f4 f5?! 2.e4!? fxe4 3.d3 : From's gambit reversed

unfortunately for you the reversed from's gambit. (swiss gambit) is almost a straight-up win for white.

I am not sure whether White really has full compensation after 2.e4 fxe4 3.Nf3 Nf6

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Amusingly, one of the hardest nuts to crack. I could not claim that 1.f4 is the best possible move, but 1...f5 surely is one of the best!

GM M. Marin, "Play the Leningrad Bird"

I suggest you go right now and educate this illiterate GM.

hmm, I've never seen 3...Nf6 before. yeah, it's probably best from me looking at it. I'd probably play the objectively incorrect but fun 3.g4

i dont understand you. Saying 

this is fine for white but saying

is lost for black. 

But yes the f5 answer to f4 is very bad. Not because of your gambit  because of the bad symetry

Bad symmetry after two moves?

Come on Preusseagro.A very bad joke.