The Tree Swallow, Tachycineta bicolor is a small bird with iridescent greenish-blue feathers above with a white chin, breast, and belly below. It is a migratory bird and spends long summers and falls in Maryland. Tree swallows are cavity nesters, and since Glenstone's streamside bottomlands are full of snags, dying branches and abandoned woodpecker holes, finding nesting opportunities is not a problem. These birds raise only one brood a year, with fledglings being fed flies, beetles and termites. Tree swallows are fast, nimble birds, often catching their prey on the wing. They are often seen flitting in and out of bluebird boxes by Alex Da Corte's sculpture As Long as the Sun Lasts, 2021, and Jeff Koons' Split-Rocker, 2000.