Evening is for the birds

It's a remarkable sight.
Every evening, between 7:30 and 8 p.m., starlings congregate in the giant, old poplar in the field behind our home. They arrive singly, or in small groups, or in flocks of a hundred or more.
The first to come settle on the top, leafless branches of the dying tree. They are soon joined by others, and the noise begins... not singing, because these are starlings, after all, but their best efforts at chirping.
The first large flock to arrive is an amazing sight, as a hundred or more birds glide across the sky, and then swoop to their chosen perches. Then another flock, and another, until the tree contains more than a thousand loud birds, at a conservative estimate.
Sometimes, they spill over into other nearby trees, including our spruces, but if we clap our hands, they soar up out of the spruce trees and elbow their way into spaces on the poplar.
We try to imagine what they are doing in this nightly gathering. Reporting in? Sharing information about the best places to find edible insects? Or is it a singles bar for starlings?
They arrive over the course of a half hour or so; by the end of the exercise, the tree is quivering like a wet Labrador, even though no other tree nearby shows any movement at all.
The noise hits maximum level, everyone is chattering at once, and suddenly, on some signal that you know humans are never going to figure out, they are off, again. This tree is not their night-time perch... it's their after-work pub. They spend anything from forty minutes to 30 seconds, for the latest-comers, and then they are off to destinations we know not of.
It is not rare to see a lone starling or two soar in just as the crowd is departing. These tail-end Charlies never land, they simply tag along at the rear of one of the new flocks heading off to -- to what? A better bar, or a starling restaurant, now that they have had their pre-dinner cocktail?
It's a fascinating phenomenon, all the more so because it lends itself to no easy explanation. Anything we try to figure out smacks of blatant anthropomorphism, so it's probably better to go all the way and call the popular tree Cheers for the Birds.
Whatever the inspiration, it's loud, it's fraught with danger for human observers under the flight paths of these thousand-plus birds, and its absolutely intriguing.
Plenty of people don't have any affection for starlings... I'm thinking they might change their minds if they saw them in this unusual behaviour. Or, they might simply have a dry cleaning bill of major proportions.