Wrapping up Texas mystery birds

Probably the biggest mysteries for me are shorebirds, despite all my attempts to learn them. After Mary and I left the SPI Bird and Nature Center, we went a bit further up the island right next to the Convention Center, where there are some hard sandflats where people fly kites, ride those sail-board-wheel thingies (???), and (apparently) drink and toss beer bottles onto the ground. We'd seen a huge flock of shorebirds and gulls and terns there when we were at the nature center, so we thought we'd get a closer look.

Here's an idea of how many birds there were--click for bigger:
I got a little too close and they all wheeled into the sky. That's the nature center in the background. Anyway, they settled back down and I got great shots of TONS of birds in addition to the various terns and gulls I showed you earlier. Here are some more mysteries:
These kinda look like snipe to me -- but there are some different birds in there too. Note the white leading edges of the wings on some of them. The one at the bottom is definitely different from the others, as is the one farthest to the right underneath that larger one. All the rest are, I think, the same kind of bird. Note also the white eyestripe on the many birds.

Some kind of sandpiper?

From left to right, a plover of some sort? a dowitcher (with long bill)? a something laying down? a young Sanderling not yet in full breeding plumage? (the whitish one) I give up.

Ah, now THESE are easy -- Black Skimmers, skimming.

Here's what I think is a Sanderling not yet in his breeding plumage:am I correct?

and here's a close-up of a similar plover to the one above in the group photo:no clue. I know from the bill that it's a plover -- the common one down there is Black-bellied, but shouldn't he have been (a)gone by early March OR (b)in breeding black plumage? Perhaps it's a female?

Any help with these mysteries would be appreciated. I also have a "sound" mystery, but unfortunately I didn't get a recording that came out. When we were at Laguna Atascosa after dark, we heard a "wheep!" sound -- the bird would say "wheep!" and then wait a second or two, then "wheep-ho!" I've listened to nightjars, goatsuckers, owls -- no clue what this bird was. Any suggestions? We never saw anything, but we heard him as dusk fell and into the dark of the night.

This is probably my last Texas post; it all seems so long ago now. I've been working like a dog lately, doing my door-to-door thing despite the almost constant rain and cold -- which can really get a body down. We had two beautiful days, yesterday and Thursday, but today we're back in the low 40s with a steady rain and biting wind.

I've done a little birding here and there, mostly while on my way to work. I passed a farmpond today in which I saw a pair of Buffleheads, a Pied-billed Grebe, and three Wilson's Snipe! That was pretty cool. Mostly, though, I've been working.

I'm also watching my tomato and pepper seedlings grow, waiting for warmer weather to come so I can start hardening them off in preparation for container gardening! I know better than to put anything outside before Memorial Day, so it'll be a while before I get any gardening updates. Right now, I'm working on some self-watering containers (from a book AB got me) and keeping my seedlings warm.