Chipkali ne gana start kia

A lizard riddle that builds slowly — three on a wall, one starts singing, two fall, and the reason is satisfying.

3 chippkalian deevar per chal rahi thein,
1 ne gana start kia
jese hi gana khatam huwa 2 gir gayain
batao kion?
?
?
?
?
Is liye k baqi 2 ne taaliyan bajai thein :-)