They have an undulating flight, but they don't 'dance' like the flock of 20 plus small birds that fairly bounces along over the trees at the edge of the meadow. Other than getting the impression that they are brownish I can't make out any detail of their plumage, but by their lively undulating flight I can tell that they're a lightweight finch, much lighter in build than a House Sparrow.
My first thought is that they're Linnets, but linnets tend to feed on the ground whereas these little birds definitely seem to be interested in the tree tops. Perhaps they are Redpolls, a finch that is even smaller than its relative the linnet? Redpolls often feed in tree tops on the seeds of Alders and Birches.
By 5 o'clock it is dark. Down on the river five or six Mallards are settling down amongst the tufts of dead grasses which are all that is showing above the water of the silty island.
What a place to spend the night!