Carery thanks for youe insights on the male duck and the identification of the female ducks.
Oddly the ebird list for western Sahara includes only one hybrid duck and that is pochard x ferruginous. I wonder why that one is included? As it happens this bird seems to look close to the picture of a pochard x ferruginous in the Collin's European guide.
Last Mauritania: Arctic skua #300 (Clements count)
Last Saudi: African stonechat #332
Last Oman: Swinhoe's storm petrel #330