1120 SW 5th Avenue, Room 1000, Portland, OR 97204
Historic In general, this subwatershed supported high species abundance and diversity because of the varied sources of food, water, and shelter found in forest and streamside habitats. Although specific records are lacking, the subwatershed probably provided habitat for migratory and resident birds, amphibians, reptiles, mammals, and invertebrates. The Oregon spotted frog and the western pond turtle were more abundant in the Willamette floodplain portion of the Miller Creek subwatershed prior to settlement, and most likely inhabited the backwater areas and lakes along the shoreline of the Willamette River.
Current Miller Creek subwatershed has some of the most intact wildlife habitat in the plan area. The Miller Creek subwatershed connects habitat in Multnomah County to the north with other subwatersheds in Forest Park. Forest Park, in turn, provides a habitat link for the Tualatin River Valley, the Coast Mountain range, the Willamette River, Sauvie Island, the Columbia River, and the Vancouver Lowlands in Washington. Skyline Boulevard, Newberry Road, and St. Helen’s Road are major obstacles to wildlife movement in this subwatershed.
Wildlife species that occur in the subwatershed include: northern flying squirrel, Townsend’s chipmunk, blacktailed deer, mountain beaver, bobcat, coyote, wandering shrew, Trowbridge shrew, shrew mole, deer mouse, Pacific jumping mouse, western pocket gopher, beechey ground squirrel, little brown bat, long-eared bat, Roosevelt elk, short tailed weasel and long tailed weasel, and evidence of black bear and cougar (scat) (City of Portland Bureau of Planning, 1995 and 2001c).
During reptile and amphibian surveys conducted throughout Forest Park in the mid-1990s, the following species were observed in Miller Creek: Pacific giant salamander (and numerous larvae), Dunn's salamander, red-legged frogs, and Pacific tree frogs (City of Portland Bureau of Planning, 1995). Other species observed in or near Miller Creek during 1990 field surveys included: several red-legged frogs, a spotted frog (state-threatened species), a western toad, and a northwestern garter snake in addition to several Pacific giant salamanders. Two salamanders that breed in forest litter, Ensatina and red-backed salamanders, are relatively common in Forest Park (City of Portland Bureau of Planning, 1995).
Bird species observed or known to occur in Forest Park include: rufous hummingbird, olive-sided flycatcher, Pacific slope flycatcher, western wood pewee, house wren, Swainson’s thrush, western tanager, blackheaded grosbeak, great horned owl, pileated woodpecker, pygmy owl, red-tailed hawk, ruby-crowned kinglet, winter wren, bald eagle, (City of Portland Bureau of Planning, 1995 and 2001c), great blue heron, band-tailed pigeon, western bluebird, and several songbirds (City of Portland Bureau of Planning, 1991b).
Remnant riparian and wetland areas adjacent to the Willamette provides habitat for a diversity of species including a significant population of red-legged frogs (City of Portland Bureau of Planning, 2000). This wetland also provides valuable rearing habitat for juvenile salmonids (City of Portland Bureau of Planning, 1991b). Other species that occur in the natural shoreline areas of this subwatershed include bald eagle, osprey, belted kingfisher, great blue heron, warblers, flycatchers, bats, voles, weasels, raccoons, woodpeckers, deer, coyote, bobcat, beaver, river otter, mink, Pacific treefrogs, garter snakes, and long-toed salamanders (City of Portland Bureau of Planning, 2000).
Assessment Very little development has occurred in the Miller Creek subwatershed. Portions of the upper watershed are experiencing residential development on large lots. This development threatens to fragment wildlife habitat in the upper watershed and could impact stream flow and water temperatures. Within Forest Park, relatively few people visit this section of the Park because of its distance from the center of Portland and the lack of trails due to an emphasis on wildlife in this part of the park.
Development and logging to the north and west threaten to isolate Forest Park. Habitat fragmentation can cause major impacts to wildlife and even lead to local extinctions (Johnson and O'Neil, 2001). Large, contiguous tracts of habitat generally support more native species than small, isolated patches. Domestic pets, especially cats, can out-compete native, medium-sized predators consuming small rodents, birds, reptiles and amphibians (Johnson and O’Neil, 2001).
Non-native or exotic species, roads, logging, development, and human intrusion impact wildlife communities. Exotic species negatively impact native species through predation, displacement, or modification of habitat, and thus threaten biodiversity (Johnson and O'Neil, 2001). Human settlement and activity have led to the extirpation or reduction of large mammalian predators, such as gray wolves, bears, and wild cats. Smaller predators (weasels, coyote, raccoons, and opossums), and secondary consumers (deer and rodents) thrive in the absence of top predators. Roads cut-off or severely hamper diurnal movements and seasonal migrations of vertebrates. Many animals die or sustain injuries while crossing roads.