Greater Skagit and Stillaguamish Delta consists of 37,000 ha (91,429 acres) of Port Susan and Skagit Bays, and is classified as Tidally Influenced Marine/Coastal Wetland. This area is a complex system of marshes, mudflats, and channels that support a wide variety of wildlife. Specifically, it is among the most important of a series of estuaries in Puget Sound that collectively support large numbers of shorebirds during winter periods and spring and fall migration. Aerial surveys of wintering shorebirds conducted in the mid-1990’s showed that this area is one of only four sites in Washington with seasonal concentrations of shorebirds exceeding 20,000 birds on a regular basis. More recently, shorebird counts have been made annually from 2007-2011, with the annual sum of maximum counts by species ranging from 30,386 to 57,171, easily meeting the 20,000 threshold for status as a WHSRN site of Regional Importance. These counts are dominated by Dunlin (Calidris alpina) and Western Sandpiper (C. mauri) which were indistinguishable in the aerial surveys.
Ownership is a mix of Washington State, local (Island County Parks), and private (TNC, Warm Beach Christian Camp & Whidbey-Camano Land Trust). The portions owned by the State, TNC, and land trust are all actively managed for wildlife values including shorebirds.
Ecology & Conservation
Conservation actions on the Stillaguamish Delta by The Nature Conservancy:
» The Conservancy owns the 4,122-acre Port Susan Bay Preserve, which encompasses much of the Stillaguamish River estuary, including 166 acres of artificially diked uplands. The property is managed in a way that benefits the vibrant estuary system and its salmon, birds and other wildlife.
» An experimental project called Farming for Wildlife was inspired by the diked wetland. This pilot project seeks to increase the value of some farm fields as habitat for shorebirds and waterfowl.
» Conservancy staff and volunteers have made great strides to control Spartina anglica in Port Susan Bay. Much of the estimated 100 solid acres that infested more than 2,000 acres of estuarine mudflat and marsh in 1997 has been eliminated. Only about two solid acres still remain scattered across the area. Strong partnerships and innovative research continue to provide focused support in effectively controlling this invasive, non-native plant.
» In collaboration with volunteers, Ecostudies Institute and Washington Department of Fish and Wildlife, the Conservancy is studying how shorebirds use the various habitats found on the preserve and throughout the surrounding area.
» Conservancy scientists are learning how climate change is affecting the estuarine environment, and using lessons learned at Port Susan Bay to guide decisions here and in other estuaries in the Pacific Northwest. As part of this process, scientists are studying how river flows and tides interact to create and sustain habitats throughout the range—from tidal freshwater to saltwater marshes.
» Conservancy scientists are also researching effective estuarine restoration techniques, including building log jams in the intertidal channels to discover whether they improve habitat for juvenile salmon and other fish.
Importance to other wildlife:
Over the last 10 years, an average of 52,000 Lesser Snow Geese and 3,000 Trumpeter and Tundra Swans winter in the Greater Skagit/Stillaguamish Delta (WDFW unpublished data). These species feed in the estuary marshes and in upland agricultural sites around the bays during the day and roost in the bays at night.
Skagit and Port Susan Bays support thousands of dabbling ducks, primarily Mallards, Wigeon, Green-winged Teal, and Pintail in winter. The 12 year average, beginning in 2000 is: Mallard: 29,680; Wigeon: 15,138; Green-winged Teal: 1,928; and Pintail: 11,957 (WDFW unpublished data).
The sandy shoreline of east Port Susan Bay (at Warm Beach) is a documented Band-tailed Pigeon mineral site. Annual counts in July indicate a minimum of 40 birds/day utilize the beach in July (WDFW unpublished data).
Thirteen Bald Eagle nesting territories, one Peregrine Falcon breeding site, 5 Harbor Seal haul-out sites, 2 Osprey nest sites, and 1 large Great Blue Heron breeding colony occur in the Delta (WDFW unpublished data).
The Greater Skagit/Stillaguamish Delta supports Federal and State listed Chinook salmon and other salmon species, shell fish, and forage fish.
Photos in progress...
District Wildlife Biologist
Washington Department of Fish and Wildlife
PO Box 1100
La Conner, WA 98257
360.466.4345 ext 265
Island County Parks Department
PO Box 5000
Coupeville, WA 98282
360 679 7331