The refrain of this one could BE a bird song:

hi-lili-hi-lo

On every tree there is a bird
Singing a song of love...
On every tree there is a bird
And every one i'd ever heard
Could brake my heart without a word
Singing a song of love...

The song of love is a sad song
Hi lili hi lili hi lo
The song of love is a song of woe
Don't ask me why i know

The song of love is a sad song
For i have loved and it's so
Hi lili hi lili hi lo hi lo
Hi lili hi lili hi lo
Hi lili hi lili hi lo hi lo
Hi lili hi lili...... hi lo