Revealing mistake: During winter at the cabin, several of the kidnapped girls are doing chores. As they are about to go back inside the cabin, the long icicles hanging on the porch eaves can be seen swinging loosely when they should be frozen in place.
Continuity mistake: During the barn dance Frank's shirt front frequently changes between a V shape (like Ephraim's) and a U shape (Like Benjamin's).
Answer: Yes it is true. They did this to prevent the birds from flying into the backdrops and becoming injured or killed.