Found this Flappy Bird Tutorial using SpriteKit and it works quite well.
Just need to add a few things: score display, music, sound effect, game over handling (currently the bird just disappeared when it died, which wasn't that user friendly), an icon...etc, and it's a fully functioning game!
Found a bug though, although collision detection was added for the ground, it wasn't added for the top of the screen. Which means I can actually fly above all pipes and keep traveling, scoring as many points as I like, until I felt tired, stopped flapping, and the bird fell to it's death...
Any way, it's great fun learning all the different techniques presented by the author. Wonder where did the author get all the images from?
Found another one here Flappy Bird tutorial, which has game score display, plus much better game over handling. Also, although I can also fly over all the pipes, I couldn't get any score as the bird didn't fly though the gap between the pipes. Looks like the second one is a better design!