The summer is racing to an end. The Agricultural Fair is this weekend, the Chilmark Community Center programs end on Friday the 16th (although I will lead their last of the season bird walk on August 20), and people are beginning to return to their homes after their summer vacations. And along with all of this, the birding is changing. Large numbers of shorebirds are being found on the flats of the South Shore and along a few of the harbors and Great Ponds. Yellow warblers are disappearing, headed for their winter haunts in the south.