Sze -
Yes, this is a White-winged Tern Chlidonias leucopterus. The head pattern - a more-or-less isolated black spot behind the eye - is strongly indicative of winter plumage leucopterus(although Whiskered Tern can very occasionally appear similar!)
The black mottling on the underwing coverts, which is clearly visible in the photographs, confirms that this is an adult leucopterus moulting from summer to winter plumage.
I suspect the bird in the 4th photo is the same bird.
david
