(DC) (Friends of the National Arboretum) Join us for a summer bird walk through the U.S. National Arboretum led by experienced guides from the DC Bird Alliance. The Arboretum’s 451 acres of green space provide a unique ecosystem within the city to find a variety of birds. On this bird walk, you’ll not only spot birds — you’ll also learn about local bird populations, bird behavior, and identification tips!