Definition: In this task, you will be given a short story. One sentence from the story is chosen. Consider the events that happen before that sentence, or are likely to have happened before it. Does any of them directly cause it, or simply make it possible? You should write your answer in the form " A >causes/enables> B". Try to use phrases and sentences from the story to compose your answer when possible.
Input: story: Chris noticed a bird's nest on the ground in front of a holly tree. He looked in it and saw three eggs. There was a worried mother bird flying around. Chris put the nest into the tree quickly and walked away. He saw the mother sitting in the nest a few minutes later.
 selected sentence: There was a worried mother bird flying around.

The nest falls >Causes/Enables> The mother bird is worried