Chimney swifts by the hundreds, perhaps thousands, gather swirl in a circle around the tall chimney at the J.S. Jenks Middle School in Chestnut Hill.  The circle becomes denser and then they begin pausing then plummeting down inside for their nighttime roost. Once they start descending, they are all down, stragglers and all, within ten minutes. At daybreak they emerge but at a more relaxed pace. In late August and early September, swifts are beginning to make their annual migration south to Florida and South America where they can continue to feed on insects on the wing.  Jane Henderson, who related the above, is shown here scouting out the Jenks nesting site in preparation for a field trip she will lead at the schoolyard for the Wyncote Audubon Society on  Wednesday September 5, 2012. Watch video interview here