Habitat

Denny Neighborhood Forest Wildlife Habitat Assessment
Lois Berner

I conducted a site visit on March 19, 2002 with Jim Sproull. We walked property and drove around most of the perimeter as well as the surrounding neighborhoods. The property is separated by roads and topography into three distinct units. The western unit is located west of Holmes Point Dr. NE. The central unit is between Holmes Point Dr. NE and NE Juanita Dr. and contains the largest stream in a deep ravine. The eastern unit is located east of NE Juanita Dr. The three units considered together provide many of the basic habitat requirements for many wildlife species. Good thermal cover is provided by the western unit. Year-round water is available in the central unit and a diversity of food sources would be found in the eastern unit.

The western unit is characterized by a relatively even-aged conifer stand predominantly composed of Douglas fir about 15 to 24 inches in diameter. The trees are spaced relatively evenly and form a closed high canopy. Regeneration is occurring under the canopy with many young cedar and hemlock evident. This unit also contains a good diversity of native shrubs in the understory layer including Indian plum, hazelnut, salal and sword fern. There are a number of dead, standing trees (primarily Douglas fir) along the western edge of this unit and may be others within the unit. Several snags (fir and alder) were observed with pileated woodpecker foraging sign (a state candidate species and King County Species of Local Importance). This area would support a variety of native wildlife species including forest birds such as kinglets, bush tits, woodpeckers, towhees, barred and western screech owls (Pamela Readdy has a list compiled from her office window overlooking this western unit), and other mammals such as coyotes, voles, raccoons, and possibly skunk. The coniferous overstory of this unit would provide good nesting and thermal cover for wildlife species. There was not much evidence of downed woody material, though this habitat feature will develop with time. Non-native plants include holly, ivy and a small amount of laurel. These non-native plant species are establishing a foothold on the property and should be controlled before they degrade the habitat. The western unit is also the site of some rather large earthworks created by bike enthusiasts. These earthworks are mounded at the base of a number of trees and will likely damage them if not removed.

The central unit is characterized by a deep ravine with a year-round stream at the bottom. This stream section is quite close to it’s confluence with Lake Washington, but it is not known whether there are any barriers to fish passage between the parcel and the Lake.

There appeared to be a number of large downed logs across the stream which may be providing additional stream channel diversity and habitat for invertebrates andamphibians. The central unit has fewer conifers and is more open with a deciduous tree canopy composed largely of mature alder, big-leaf maple and cottonwood. Some of the cottonwoods are quite large and could provide nesting substrates for owls or hawks. The understory includes a mix of native shrubs and herbs including Indian plum, salmonberry, and sword fern. There is more ivy and non-native Himalayan blackberry in this central unit than was evident in the western unit, but it still is not pervasive throughout the siteand controls efforts should have a high likelihood of success. The presence of year-round water in the protected ravine setting provides an important habitat component for many species of wildlife that is increasingly scarce in urban settings. This ravine probably attracts a wide diversity of bird and mammal species, such as mountain beaver, as well as potentially supporting amphibians and fish species. There was little evidence of human use in the ravine as most of this unit is relatively inaccessible due to the steep slopes of the ravine and the dense vegetation.

The eastern unit is composed of a mix of deciduous and coniferous tree species that appear to vary more in size and age than the other units. The tree canopy of this unit includes mature alder, madrone, and Douglas fir. The understory includes salal, Indian plum, the native creeping blackberry, and stinging nettle indicating a more open forest canopy. There is little evidence of forest regeneration in this unit but there are also fewer non-native plants present. There are a number of snags, mostly alder, that presented sign of pileated woodpecker foraging. This unit included a number of plywood “forts” and small excavations presumably constructed by neighborhood children. The diversity of tree and shrub species in this unit would provide food for a wide variety of wildlife species.

The surrounding neighborhoods are relatively well forested, extending and buffering the wildlife values of the Denny Neighborhood Forest property. The property is also very close to the O.O. Denny Creek Park and the Big Finn Hill Natural Area. A relatively high degree of connectivity between the Forest property and the parks to the north is maintained by the existing mature forest cover in the intervening neighborhood. The Big Finn Hill Natural Area connects directly to St. Edwards State Park. This high degree of connectivity and the combined size of the parks and natural areas further enhances the functionality of the Forest property. The Forest property is not a small isolated piece of forest land within an urban context. Rather it is a piece of a much larger functional system of forest lands, riparian areas and wildlife habitats.