Editor’s note: Due to expected bad weather tonight’s walk has been changed to Saturday. An excursion to witness what organizers describe as “one of the most fascinating birding spectacles in all of New Jersey” will take place Saturday, Sept. 14, 8 a.m., when hundreds of Chimney Swifts enter their migratory roost at Buzz Aldrin School. The trip begins at Hilltop Reservation, corner of Courter Lane and Mountain Avenue in North Caldwell (turn right on Mountain Ave from Bloomfield Ave.) Attendees will meet at area of the parking lot nearest to dog park. At the conclusion of the walk, the group will drive over to the Chimney Swift roost at Buzz Aldrin School on the corner of Bellevue Ave and Norwood Avenue in Upper Montclair, where hundreds of Chimney Swifts enter their migratory roost at Buzz Aldrin School. In past years, upwards of 500 birds have entered the Chimney at dusk.