We have wrens nesting in a woven roosting pouch in our porch in Middletown. Or...we did. When the young were two days old, we became aware that the busy parents had gone. I found the nest empty. The next day, we watched a Nuthatch (also on territory around the house) explore our House Sparrow's nest in the eaves. Could it have...? I see no reference to nestlings as Nuthatch prey in the literature.