Forster's Tern

I saw some beautiful terns near the Salton Sea, at the wetlands off McDonald Road near Niland, and had a hard time trying to distinguish whether they were Forster's terns or common terns. I saw at least three of them, possibly more. 

I found a good article that provides ways to distinguish the two. A breeding Forster's tern (as opposed to the common tern) has a full black cap, pure white underparts (as opposed to light gray underparts), long tail streamers that project beyond the wingtips (common's do not), an orange to red based bill (the Forster's is stouter, more orange and more black on the outer end), and primaries that are silver white above and with no dark markings (outer primaries are somewhat grayer bordered by a dark streak or wedge that cuts across the wing at about mid-primaries). At close range the tail streamers are dark on the inner web, white on the outer web, and the tail is pale gray (as opposed to white). There is a white rump between the pale gray back and tail. The legs of the Forster's are notably longer. Based on the foregoing, I believe what I saw were Forster's terns. 

The tail streamers go beyond the primaries by a little bit. 

It has white underparts. 

The bill is orange and has quite a bit of black on the end. 

Pale silvery gray to white primaries.