The bird is one of many basic figures and quite easy to fold. There are some figures which are based on the bird like the crane or the swan for example. The basic form of the bird is the Preliminary Fold. You are just two foldings away from the bird folding.

Don't forget to retighten every fold with your fingernail!

The single steps of folding the bird:

Step #1:
Fold the raw edges of the top layer in so that they lie exactly along the center folding and open the foldings afterwards.
Open the top layer and fold theleft and the right side in. Bring the top flap down again.

Step #2:
After you have turned the paper around redo step one.

That's your folded bird.