September 12:  This time of year many of the warblers passing through New England are first-year birds, which bear little resemblance to the gaudy-colored springtime breeding-plumaged adults. Here are a first-year Black-throated Green Warbler from yesterday at Bluff Point, and, from Comstock Park this morning, a first-year Chestnut-sided Warbler just beginning to show the barest trace of the namesake reddish “chestnut” color on the flank.