Sometimes it's best to make the first move, like when you're a bird hoping to snack on a multi-legged creature with no visible means of escape. However, all this polite would-be predator manages to do is follow the insect, opening its mouth from time to time.
The bashful bird gives the impression that it assumes its prey is supposed to get inside its mouth simply by itself, as if the insect has been waiting to be eaten all its life.