Tunisia issued this set in 2004. From left to right, the stamps depict the male and female of the white-headed duck (Oxyura leucocephala), the ferruginous duck (Aythya nyroca) and the moussier's redstart (Phoenicurus moussieri). The final stamp has a single marbled duck (Marmaronetta angustirostris) as there is no sexual dimorphism in this species.