Predation of vertebrates by Mallards ($Anas\; platyrhynchos$) has rarely been documented and only in relation to fish and amphibians. Mallard foraging behavior was observed at a reservoir bordering Semenic-Caras Gorges National Park in southwest Romania. A group of Mallards comprising one adult female and 10 subadults was recorded hunting, killing and consuming hatching year passerine birds of two species, a Grey Wagtail ($Motacilla\; cinerea$) and a Black Redstart ($Phoenicuros\; ochruros$). These are the first records of hunting of birds by wild Mallards. This extraordinary new behavior represents substantial diet expansion for this widespread and abundant duck species.