Female rosy-billed pochard on the left

First record of parasitism by black-headed duck with the host. The black-headed duck is the only obligate parasite. It parasitizes many aquatic species and in this case the host is a rosy-billed pochard. Since July there have been frequent records of black-headed duck, which makes us presume there may appear more cases. So, when you spot any water bird family, check all chicks are the same. There may also be facultative parasitism.
According to the bibliography these ducklings leave their host parents very soon. This photo was taken in the Duck Pond from the burnt viewpoint. 

First record of parasitism by black-headed duck with the host. The black-headed duck is the only obligate parasite. It parasitizes many aquatic species and in this case the host is a rosy-billed pochard. Since July there have been frequent records of black-headed duck, which makes us presume there may appear more cases. So, when you spot any water bird family, check all chicks are the same. There may also be facultative parasitism.
According to the bibliography these ducklings leave their host parents very soon. This photo was taken in the Duck Pond from the burnt viewpoint.