The Susitna Flats IBA is an expansive coastal lowland on the northwest side of Cook Inlet that extends from Threemile Creek (north of the village of Tyonek) east to Pt. McKenzie. The Susitna River divides the site roughly in half. The Little Susitna River delta lies to the east; the Beluga, Theodore, Lewis, Ivan rivers transverse the western portion of the site. The area encompasses about 360 km2 of unvegetated intertidal flats and an equal amount of vegetated intertidal sedge meadows intersperced with numerous small ponds and lakes. As a result of the 1964 Alaska earthquake much of the intertidal (both vegetated and unvegetated) area subsided as much as 0.7m., which changed large portions of the area through geophysical and vegetation successional processes.

Ornithological Summary

The most noteworthy bird group on the refuge is waterfowl. Spring migration of ducks, geese and swans number well in excess of 100,000 birds [8]. Total daily counts of waterfowl can exceed 36,000 birds during spring migration.
Total high counts for all [shorebird] taxa using the site exceeds 30,000 birds. The diversity of species is among the highest at any site in Cook Inlet, but overall numbers of any one species, except for Rock Sandpipers and Hudsonian Godwits, was relatively low. The site's principal importance is to the nominate race of the Rock Sandpiper (C. p. ptilocnemis), of which virtually the entire population resides on the area between early Oct. and late April. [2]
Susitna River Flats qualifies as a WHSRN site based on several criteria. It qualifies as a Regional Reserve based on total numbers, both for all species combined and for Rock Sandpipers. It also qualifies as a Hemispheric Reserve based on the percentage (>95%) of the population of the nominate race of Rock Sandpiper that uses the site and would qualify as an International Reserve based on the percentage of the species population of Rock Sandpiper (<150,000 for all four Alaska forms combined: Robert E. Gill).

The Susitna Flats State Game Refuge has spectacular spring and fall concentrations of migrating waterfowl and shorebirds. Usually by mid-April, mallards, pintails, and Canada geese are present in large numbers. Peak densities are reached in early May when as many as 100,000 waterfowl are using the refuge to feed, rest, and conduct their final courtship prior to nesting. The refuge also hosts several thousand lesser sandhill cranes and upwards of 8,000 swans. Northern phalaropes, dowitchers, godwits, whimbrels, snipe, yellowlegs, sandpipers, plovers, and dunlin are among the most abundant of shorebirds. Most of the ducks, geese, and shorebirds move north or west to nest in other areas of the state. About 10,000 ducks mostly mallards, pintails, and green-winged teal, remain to nest in the coastal fringe of marsh ponds and sedge meadows found in the refuge. Recently, Tule geese, a subspecies of the greater white-fronted goose, have been discovered to nest and stage on Susitna Flats. In the fall, migrant waterfowl and shorebirds once again arrive in growing numbers to rest and feed on sedge meadows, marshes, and intertidal mud flats. [6]

Species of conservation concern (Alaska Watchlist) present in the Susitna Flats area that do not meet criteria include: the Red-throated Loon ; Golden Eagle; Greater White-fronted Goose (Tule); Long-tailed Duck; Black Scoter; Barrow's Goldeneye; Wandering Tattler; Whimbrel; Surfbird; Olive-sided Flycatcher; Gray-cheeked Thrush; and the Blackpoll Warbler (8).

Waterbirds: passage; maximum 26,357; 4aiii

Taverner's Goose: Passage; 1982; 876; 4aiii.

Conservation Issues

Each year approximately 10 percent of the waterfowl harvest in the state occurs on Susitna Flats, with about 15,000 ducks and over 500 geese taken.


Susitna Flats State Game Refuge (100% overlap). In 1987 there were 13 private inholdings in the refuge, it is not clear how many exist now.


The refuge encompasses approximately 301,947 acres of which about 22 percent is tidal, 11 percent is ocassionally flooded salt marsh and meadow, and 67 percent is a combination of lakes, bogs, low shrub and mixed lowland forest (8).

Shoreline: 140 km
Vegetated Intertidal: 115 km2
Unvegetated Intertidal: 369 km2

Broadleaved deciduous forest; native coniferous forest; mixed forest; scrub; mudflats/sandflats; standing fresh water; river/stream; blanket bog

Land Use

It was nominated as a WHSRN site, but never formally designated as such.

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