Genetic & Developmental Defects or Injuries
American Black Duck x Mallard Hybrid
Two individuals have been found with similar defects on the upper bill as either a developmental malformation or an injury.
Case 1 
This male has come to Jessica's pond for at least five consecutive winters (2013-2017) and hangs out with Mallards. The last three years a female American Black Duck has accompanied him. He was not seen since the spring of 2018.
American Black Duck x Mallard hybrid-972
Case 2 
This male was seen in the winter of 2018-19. Note the defect is on the other side of the bill.
American Black Duck x Mallard hybrid-047