Some of my doubts are answered when I got the chance upon a Rufous Woodpecker (Celeus brachyurus). The woodpecker start to peck on the branch and after a while, it uses the tongue to do the finishing kill.
This crack on the branch gave the woodpecker a easier meal.
No doubt that the tongue play a very important role in woodpeckers' feeding behavior. However, I still have no clue on how exactly did they use their tongue to catch their preys. Do they have a sticky tongue like the lizards and use it to 'stick' their preys?
Perhaps video recording will help...