With its woodlands, low-lying prairies and many acres of ponds, Barker Reservoir has helped make Houston's ozone-choked air less foul, and more fowl. The nature preserve is a pre-eminent spot for birding within the city limits, particularly during winter months. Assorted songbirds, waterfowl, hawks, blackbirds, owls and other species thrive in the sanctuary, which lies west of Highway 6, between I-10 and Westheimer. White-tailed hawks, black-shouldered kites, flycatchers, warblers and a variety of sparrows animate the refuge. Restored wetlands have attracted white ibises, great blue and green herons, egrets and other shorebirds eager to troll for crawfish and tadpoles. Miles of nonvehicle roads and running trails allow wide-ranging access.