Birding Puzzles - Caspian, Royal, or Elegant Tern?

It was crowded at the beach Monday even though it was grey.  Identifying gulls drives me crazy.  There are so many that look alike, and the juveniles change each year too.

I did notice that these had 3 dots on the ends of their black wings and yellow beaks with black tips and bit of orange.  The legs are greyish/pink.  (I'm only looking at the mature birds now.)  So there are several gulls that come close - Western gulls seem to have the black on the bill as juveniles and the orange as adults.  Maybe these are moving from one to the other.

But then I saw these guys.

I'd seen them before, but couldn't remember what they were called.  I thought of Bonaparte - but they have more rounded black heads.  Emperor?  When I got home I saw the name - Elegant Gulls.  But there were two other, very similar, terns.

From Sibley's Field Guide To Birds of Western North America  (click to enlarge)  Check the heads.

One's black clear across.  The other two had white foreheads. The book shows the whiter forehead from August to February and the blacker forehead from March to August.  It's mid-February now, so they could be changing. In any case that would seem to eliminate the Caspian Terns.   Now look at them compared to the gull.

The gull (in front) is much bigger, and the Elegant Terns are the smallest of the three terns.  Now look at them flying.

The wingtips of the Royals in the book seem to be darker than the Elegants.  I'm guessing these are Elegants.  (And last time I found one like this here, my birder friends said it was an Elegant.  So I'm hoping Dianne will check and confirm.)