owl, hairy woodpecker, Bewick's wren, orange-crowned warbler, osprey, northern pygmy-owl, and hermit thrush are among the more than 112 species of birds that have been observed in the park. In Balch Creek Canyon adjacent to Forest Park, the Audubon Society of Portland maintains a wildlife sanctuary with more than of trails, a wildlife care center, and avian exhibits. Amphibian species frequenting the Audubon Society pond include rough-skinned newts, Pacific tree frogs, and salamanders. Pressure from habitat loss, pollution, hunting, and urban development has reduced or eliminated the presence of wolves, bears, and wild cats and has led to increased numbers of weasels, raccoons, and other small predators. Invasive plant species such as English ivy have made the habitat simpler and less supportive of native insects and the salamanders and other amphibians that feed on them. Roads in the area severely hamper the movement of large animals. Multnomah County has designated Northwest Cornell Road and Northwest Germantown Road as "rural collector" streets, carrying traffic of less than 3,000 vehicles per day but more than streets designated as "local roads". Dogs allowed to run (illegally) off-leash in the park pose threats to birds, fish, and other wildlife. Creeks About of rain falls on Forest Park each year. Many small creeks, only a few of which are named, flow northeast through the park from the ridge at the top of the West Hills to the base of the hills near U.S. Route 30. The five named streams from east to west are Balch Creek, Rocking Chair Creek, Saltzman Creek, Doane Creek, and Miller Creek. Rocking Chair Creek is a tributary of Saltzman Creek. After leaving the park, the streams pass through culverts and other conduits before reaching the Willamette River. These conduits block fish migration to and from the Willamette River except on Miller Creek, where the conduits are short and have been modified to assist the fish. Near the east end of the park, the free-flowing reaches of Balch Creek support a population of resident cutthroat trout. Near the west end, furthest from the city center, Miller Creek retains much of its historic nature and supports a greater diversity of aquatic organisms than other Forest Park streams. Biological field surveys of Miller Creek in 1990 noted sea-run cutthroat trout, coho salmon, and short-head cottid, as well as abundant macroinvertebrate species including stoneflies, mayflies, caddisflies, water striders, and crayfish. History Before settlers arrived,