"When the pateke was hit he had bad injuries and wouldn't have survived in the wild - he had a serious head injury and damaged eye. After receiving treatment over four days he was displaying signs of wanting to return to the wild (wanting to swim) and by returning him, his recovering will be sped up," she said.
"Pateke recover better in their natural environment and away from the stress of captivity and handling and we thank the members of the public who brought him in."
She said Pateke are still at risk of extinction if the threats to the species are not managed, including mammals such as cats, dogs, mustelids and pukeko and habitat loss through wetland drainage, forest clearance, and estuary reclamation.
Hunting, roadkill, dry spring and summer conditions which reduce food abundance and competition and hybridisation with mallards were also threats.
Ms Monteith asked anybody who saw unusual looking ducks, especially if they were injured, to contact the DOC emergency hotline 0800 DOC HOT (0800 362 468).