A guide from the Tucson Audubon Society leads a birding walk among the two ponds, mesquites and cottonwoods along Tanque Verde Wash starting at 7 p.m., Tuesday, Sept. 11; free. Meet at McDonald's, on the northeast corner of the Catalina Highway and Tanque Verde Road. The walk will finish by noon. Call 629-0510, ext. 7011, for more information.