This site encompasses the Skagit River drainage from Skaist Creek in the southeast to Twenty-eight Mile Creek in the west, and includes the Sumallo River drainage northwest to the Manning Provincial Park boundary and the Snass Creek drainage.
The Skagit-Sumallo Important Bird Area is comprised of a series of interconnected valleys, forested with Western Hemlock, Western Red Cedar and Douglas Fir. At and beyond the upper limit of the site (1250 m), the habitat changes to a subalpine forest with Engelmann Spruce, Subalpine Fir, Amabilis Fir and Mountain Hemlock. Most of the forest on this site is old growth.
Because this site is within a highly faulted area of the Cascade Mountains, the terrain is very rugged and rocky. Most of the rivers in the area flow into deep valleys with relatively high gradients. The Sumallo River, however, has some slow moving, meandering sections. The nationally endangered Tailed Frog, a species that requires cold mountain streams in unlogged areas, is found at this site.
The Skagit-Sumallo IBA is one of only a few sites in Canada that consistently has breeding pairs of the nationally endangered Northern Spotted Owl. In most years, four Northern Spotted Owls can be found at this site; in total the Canadian population is estimated at a maximum of 100 pairs.
The Sumallo and Skagit Rivers also provide breeding habitat for Harlequin Duck, Common Merganser, and American Dipper. Black Swifts are also thought to nest on some of the valley walls that are situated near small waterfalls. Forests in the surrounding area provide habitat for species characteristic of coastal coniferous forests, including Northern Pygmy-Owl, Vauxs Swift, Red-breasted Sapsucker, Pacific-slope Flycatcher, and Varied Thrush.
BirdLife International (2020) Important Bird Areas factsheet: Sumallo River/Skagit Valley. Downloaded from http://www.birdlife.org on 03/12/2020.