Across all boxes occupied by BFDV - positive birds ( parents or nestlings ) , no nest swabs were BFDVpositive before breeding , 36 . 4 % ( 95 % CI 10 . 9 - 69 . 2 ) were positive during breeding and 9 . 1 % ( 0 . 2 - 41 . 3 ) remained positive after breeding .