Site Complet

Oak Hammock Marsh WMA (MB010)


Oak Hammock Marsh WMA (MB010)

Winnipeg, Manitoba

Latitude 50,190°N
Longitude 97,133°O
Altitude 233m
Superficie 67,56km²

Description du site

Situated approximately 30 km north of Winnipeg, Oak Hammock Marsh is a man-made freshwater marsh restored from a remnant of the former St. Andrews Bog and marginal agricultural land. Beginning in 1967, Manitoba Natural Resources, Ducks Unlimited, the federal government, volunteer conservation organizations and local landowners began the restoration. It is a very flat area characterized by a series of dykes, water basins and artificial islands, which are managed to provide wetland habitat. Water enters the wetland by artesian wells and through Wavey Creek, then flows south through the man-made basins, and empties out of the marsh into Parks Creek, a tributary of the Red River. The area is about one-third wetlands and two-thirds uplands. The vegetation is a mix of grasses, sedges, and other herbaceous plants Phragmites communis, cattails and bulrushes are among the more common plants. The uplands contain substantial amounts of lure crops that are managed for waterfowl, as well as the only treed area, a small bluff of oaks and aspens in the southeastern corner.


Oak Hammock Marsh is perhaps Manitobas best- known natural area. At least 106 species of birds have bred and 296 species in total have been recorded in this relatively small area. Large concentrations of marsh birds are one of the reasons for its importance. About 5,500 pairs of breeding Franklins Gulls have been recorded, representing at least 1.6% of the North American population (based on upper level population estimates). A colony of as many as 70 pairs of Black-crowned Night Herons represents approximately 1.4% of the Canadian population. Other species of interest that are reported occasionally (and may breed) at Oak Hammock include Least Bittern, Yellow Rail and Red-headed Woodpecker (all nationally vulnerable species). In the spring, large numbers of shorebirds stop at Oak Hammock. Peak numbers recorded are 16,759 birds in 1981. Counts made of single species suggest that this number is low. For instance, 7,000 White-rumped Sandpipers (1.8% of the global population), 5,000 Short-billed Dowitchers (1.6% of the global population), 600 Hudsonian Godwits (1.2% of global population) and 5,400 yellowlegs have been recorded here. Note that these percentages are uncertain due to limited data on populations of northern-breeding shorebirds. The numbers of these shorebirds only occasionally reach the levels indicated, and are largely dependent on the timing of the lowering of water levels in the cells and the availability of suitable habitat outside of the site (causing the shorebirds to disperse more).

During fall migration many species use Oak Hammock Marsh as a stopover site. Numbers in excess of 250,000 Lesser Snow Geese have been observed, which accounts for about 8% of the Hudson Bay (Mid-continent) population. An impressive 200,000 Canada Geese have been recorded at the site. As many as four subspecies were mixed in the flocks (Giant, Eastern Prairie, Short Grass Prairie and Tall Grass Prairie) with each one almost certainly surpassing their respective continental thresholds. Mallard have been recorded in numbers as high as 70,000, such as on November 14, 1993. Coots are also extremely well represented here, with 2.2% of the North American population, or over 30,000 individuals having been found.

Many other species are found in abundance including nesting Eared Grebes, and in autumn, Yellow-headed and Red-winged Blackbirds and Bank Swallows.

Enjeux de conservation

Oak Hammock Marsh is a provincial wildlife management area, has been established as a Ramsar site since 1987, is a Western Hemisphere Shorebird Reserve Network site and is the site of the national office of Ducks Unlimited Canada. Manitoba Conservation actively manages the site for wildlife, with a controlled hunting area. It is very popular for both wildlife viewing and hunting.

The lands surrounding the marsh, which are privately owned, are at risk for escalating urban and industrial development. This could affect the importance of this area as a stopover site for migrating waterfowl. Overuse of artesian well water sources may also potentially affect the viability of the wetlands.

Catégories ZICO Habitats Usages Menaces Potencielles ou Existantes Status de Protection
Bernache du Canada
Nombre Année Saison
2 000 - 100 0002016Automne
4 025 - 9 2502016Printemps
3 200 - 12 0002015Automne
2 000 - 8 9652015Printemps
1 800 - 3 0002014Automne
2 0002014Printemps
5 000 - 9 0002013Automne
2 0132013Printemps
2 000 - 4 0002012Automne
2 000 - 2 7502011Automne
4 9252011Printemps
2 500 - 20 0002010Automne
2 000 - 5 0002009Automne
30 0002001Automne
20 0001999Automne
3 0001999Printemps
4 0001998Automne
8 0001998Printemps
2 0001996Automne
100 000 - 200 0001995Printemps
100 0001995Automne
300 0001979Automne
Bécassin roux
Nombre Année Saison
5 0001985Autre
Oie des neiges
Nombre Année Saison
20 0002001Automne
20 0001999Automne
250 0001996Hiver
Mouette de Franklin
Nombre Année Saison
11 0001995Été
Quiscale rouilleux
Nombre Année Saison
27 - 6402016Automne
Bécasseau roussâtre
Nombre Année Saison
Pie-grièche migratrice
Nombre Année Saison
Oiseaux aquatiques
Nombre Année Saison
400 0001979Automne
Barge hudsonienne
Nombre Année Saison