fecal sac. The feces of young nestlings are encased in a mucous membrane. This makes it easy for parents to keep the nest clean by removing feces. A parent will usually carry and drop the fecal sacs at some distance from the nest to keep the nest's location less obvious to predators.
House Wren chicks usually stay in the nest for a little more than two weeks before fledgling. If that holds true for this group, they should fledge during the first week of July.