To dream of a birdhouse represents the intention to support freedom or independence. Enjoying seeing other people be free. It may also reflect your support of others overcoming or transcending their problems. Giving others the opportunity or free time to develop themselves. Enjoying others thriving. Possibly a symbol for support from family.
To dream of an empty or unused may represent feelings about being encouraged to do whatever you want.
Negatively, may represent freedom being given to you by others because they get to use you. Freedom under insensitive or dangerous conditions. Terrible or abusive parents that let you do whatever you want as long as they don’t have to show you they love you.