Update, these birds were later identified as Lesser Crested Terns (Charrán Bengali / Sterna bengalensis).
After a phone call from friend Juan Perez about a reported sighting of two Royal Terns (Charrán real / Sterna maxima) seen on Tuesday at the Embalse I headed over there this morning (Wednesday) to try and see them. I arrived and started to scan the lake paying particular attention to the buoys floating around the Yacht club but drew a blank, so I had a look in the area where the Rio Cubillas comes into the lake but that was also quiet. I could not find a single wader and only picked up Mallard (Anade Azulón / Anas platyrhynchos), Eurasian Coot (Focha Común / Fulica atra), Common Moorhen (Gallineta Común / Gallinula Chloropus), 4x Grey Herons (Garza Real / Ardea cinerea), White Wagtail (Lavandera Blanca / Montacilla alba) and a few Linnet (Pardillo Común / Carduelis cannabina). I stayed on site for another couple of hours and scanned the lake several times but the birds had obviously just been passing through and were only seen and photographed (cuaderno-campo "Aves granadinas) by one very lucky observer. In the area I also saw Azure-winged Magpie (Rabilargo / Cyanopica cyanus), Barn Swallow (Golondrina Común / Hirundo rustica), Cetti’s Warbler (Ruisenor Bastardo / Cettia cetti), Common Chiffchaff (Mosquitero Común / Phylloscopus collybita), Common Crossbill (Piquituerto Común / Loxia curvirostra) and a male Marsh Harrier (Aguilucho Lagunero Occidental / Circus aeruginosus) which passed through heading south.
I then headed home and spent a couple of hours up on the terrace where things were also quite quiet but I did get a fly over Hawfinch (Picogordo / Coccotraustes coccotraustes) which was another new speices for the garden, distant views of an adult Golden Eagle (Águila Real / Aquila chrysaetos) and had the pleasure of watching hundreds of Barns Swallows moving through heading south with a back drop of the first snow of the winter on Sierra Nevada!!!!