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Site description (2001 baseline):

Delta Marsh is a large wetland comprised of wide shallow bays, sloughs and meadows. It stretches westward from St Laurent to Lynch Point along the southern end of Lake Manitoba. The marsh is separated from the lake by a sand ridge covered with deciduous trees including green ash, Manitoba maple, hackberry, willow and cottonwood. The hackberry stand is the northernmost location for this species within Manitoba. The ridge and associated deciduous forest acts as a natural migrational corridor for landbirds migrating to and from the boreal forest and aspen parklands to the west of Lake Manitoba. The 17,000 ha marsh is one of the largest of several marshes in the Lake Manitoba basin.

Large numbers of both diving (Canvasback, Redhead, Lesser Scaup) and dabbling (Mallard, Gadwall, American Wigeon, and Northern Pintail) ducks stage in the marsh each fall. Up to 100,000 waterfowl have been detected during aerial surveys (no aerial surveys have been completed since 1991). The number of geese using the site has increased from historic levels with Canada Geese and Snow Geese staging here in large numbers during both spring and fall migration. Ruddy Turnstones congregate in large numbers, such as 1,000, on June 2, 1993.

Large numbers of landbirds also make use of the site. Some indication of the significance is reflected in the banding totals reported by the Delta Marsh Bird Observatory. Between 1995 and 1997, the number of landbirds banded in a single season ranged from 7,500 to more than 9,000 individuals suggesting even higher (much higher) totals of birds migrating through or breeding in the area. In 1996, a total of 3,000 Yellow Warblers and 1,100 Tennessee Warblers were banded. More than 300 individuals of several other landbird species (Yellow-rumped Warbler, American Redstart, White-throated Sparrow, Least Flycatcher, Ruby-crowned Kinglet, Common Yellowthroat, and Song Sparrow) are also regularly banded each season. Up to 50,000 Tree and Bank swallows have been estimated during daily censuses.

Concentrations of over 1000 Western Grebes during migration (1996) and over 1000 pairs breeding (1979), and over 1000 Franklin Gulls have also been observed.

Approximately 16,600 ha of the land is in public ownership as provincial Crown lands administered by the Wildlife Branch of the Manitoba Department of Natural Resources. This provincial crown land is designated as Heritage Marsh. An additional 2,000 ha of this area is protected as a game bird refuge and 7,700 ha as public shooting grounds. The remaining land is under private ownership.

The Delta Marsh is a major waterfowl staging area and was designated as a Wetland of International Importance in 1982 under the Ramsar Convention. The Delta Waterfowl Research Station, which controls 1,600 ha of the marsh, has been conducting waterfowl studies since 1938. A second research station, the University of Manitoba Field Station, has been conducting landbird research since 1964. In 1995, the Delta Marsh Bird Observatory was established as part of the Canadian Migration Monitoring Network to monitor migration at these sites during spring and fall migration.

Sections of the west portion of the marsh are periodically flooded by the Portage Floodway (a flood control structure), causing excessive siltation and vegetation growth. Threats to the surrounding area include pressures to develop additional cottage sites and recreational facilities on nearby Lake Manitoba beaches.

Management plans for water control have been proposed by the province in 1978 and Ducks Unlimited Canada in 1981.

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Delta Marsh (Canada). Downloaded from https://datazone.birdlife.org/site/factsheet/delta-marsh-iba-canada on 24/12/2024.