Regarding the Tibetan Sand Plovers, note rather short, blunt-tipped bills, rounded head with combination of white forehead, well-marked supercilium, darker ear coverts and broad, often rounded-tipped pectorals/breast-band. Greater has a longer, heavier, more pointed bill with a longer nail, narrower near complete breastband and longer legs often paler in colouration. The very similar and potential vagrant Siberian Sand Plover has a stubbier (i.e proportionally short and thick) bill, shorter legs, near-complete pectorals (like Greater) and, when present, has grey blotching to the sides and/or rear flanks. The superficially similar Kentish Plover is noticeably smaller with slighter bill, a white nuchal collar, narrower pectoral 'pegs' and its behaviour is more frenetic.
Re Whiskered Tern note combination of head pattern, restricted black through eye and streaked grey crown, rather deep-based bill and long legs.
Hope this helps.
Grahame
