Can't tell if the birds are supposed to be an instant game over or not. It can seem like the game is wigging out on you. If they are instant game over, maybe add a flash on santa when colliding, and bring him down quicker.
Speaking of which, when you go below the screen, you shouldn't have to wait quite so long to restart the game. It seems like the game goes on for a good 4 seconds afterwards. Should be half that at most.
If you are worried about difficulty, you could just slow the game down a bit (maybe 20%).
Also, here's a little tip: it's always good to make your player collision field a little smaller than their actual sprite. If somebody barely clips a bird and they survive, they aren't gonna worry too much about it...but if they think they should have collided and they do, it's infuriating. Err on the side of leniency.
Otherwise, it's pretty good.