Answer:
If one way of doing something keeps failing, try another way.
Explanation:
The theme of a story refers to the message that the author wants to relay to the readers. It is the lesson that one can take away from the story, that one can learn after reading the story.
In the given story "For the Birds", the author shows Philip trying to help maintain a birdhouse. Even though his plans to keep the birdhouse remain on the branch, his acts didn't work. But he did not give up and kept on trying until he succeeded.
Thus, the theme of the story is that if one thing doesn't work, try another way.