Stunning shorebird migration zig-zags into Grays Harbor

It's late April and the sun is just beginning to rise over the Bowerman Basin, a muddy bay in Washington's Grays Harbor.
Very little mud is visible right now. One of the highest tides of the month, 8½ feet, is covering much of the mud. Tens of thousands of shorebirds are covering the rest. And more shorebirds are on the way.
Over the span of a few weeks, maybe a million shorebirds will stop here. The flock consists mainly of western sandpipers, dunlin, two varieties of dowitchers, and plover.
They're on their way to breeding grounds in Alaska and northern Canada, but given that some started in Chile and Argentina, they tend to take a few regular breaks on their way north. Grays Harbor is one of the few major stopovers.
As the tide begins to turn, a flock of maybe 1,000 shorebirds, flies into the basin in a tight formation, hugging the shoreline. They land together on a tiny patch of mud smaller than the footprint of a tiny house. Then an even larger group flies in. And another. And another.
They don't really need to spread out. Within one square yard of mud, there may be 50,000 invertebrates within an inch or two of the surface. The high tide washes in the amphipods; the receding tide reveals the all-you-can-eat buffet.
After a few minutes, the flock of shorebirds, now numbering in the tens of thousands, takes off all at once and zig-zags to another patch of mud. And more shorebirds join in all the time.
The sheer number of birds is impressive enough, but the formation flying is simply stunning.
While the flock is made up of a few different kinds of birds, they all generally have white breasts and brown backs. Depending on the direction it's flying, the mass of birds can appear all brown or all white. Occasionally, the flock changes directions and the mass of birds gradually changes colors.
The display is even more impressive when the flock does a quick jog around an obstacle or zig-zags to hug the shoreline. Then you get to see a band of the opposite color move through the flock. It appears more precise than the "wave" at a football game and yet quieter than someone watching the game at home alone.
Bowerman Basin, part of the Grays Harbor National Wildlife Refuge, is one of the best places to see the show. It's the last part of Grays Harbor to be covered by high tide and the first to be exposed, so the shorebirds tend to congregate there. During very high tides, the high water pushes the birds closer to a boardwalk with several viewing decks.
The best time to see the shorebirds is during the last few weeks of April and the first part of May within a couple hours right around high tide. It's such an amazing sight to see, I go nearly every year.
(I'm editing some video of the display. To find out when it's finished, become a LivingWilderness Facebook fan.)