To hear these bird songs, you must have the correct software. Newer browsers seem to have no difficulty playing the sounds. The bird songs will play if you have the correct plug-in for your browser. Anyway, you have nothing to lose by trying.
Click on one of the bird names on the left, and a picture should appear to the right and the sound should play repeatedly. Click any bird name in turn to hear it. When you have had enough, click the "Exit from bird songs" at the top or the "return" from the list of birds. Your browser's Back button only takes you to the previous bird song. Good luck.