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Marais de Saint-Timothée (QC158)


Marais de Saint-Timothée (QC158)

Saint-Timothée, Québec

Latitude 45.276°N
Longitude 73.957°W
Altitude 47 - 49m
Area 3.35km²

Site Description

The Saint-Timothée marsh borders the north side of the Canal de Beauharnois roughly 25 kilometres to the southwest of Montreal. The Canal de Beauharnois is another IBA and a branch of the St. Lawrence River. The Saint-Timothée marsh is a dammed section of marsh and pond managed by Ducks Unlimited (Canards Illimités). Much of the surrounding land is agricultural.


The Saint-Timothée marsh hosts a rich diversity of marsh birds and other water birds. During the site assessment conducted in the late '90s leading to the IBA designation, three notable bird species, i.e. Black Tern, Great Egret, and Least Bittern (a species that is designated as threatened in Canada), were found in nationally significant numbers. At that time, approximately 100 Black Terns were using the site during the breeding season, but this species was not found in 2013. Sixty-five Great Egrets were counted here in the summer of 2000. This is roughly 10% of Canada's Great Egret population. 18 Least Bitterns were counted during a survey conducted in 2010, and some nests were discovered in the marsh which is now considered one of Québec's 10 most important sites for this species. After the breeding season, immense numbers of swallows are sometimes found in the marsh. On one occasion 100,000 Tree Swallows were counted, and on another 800 Bank Swallows. The swallows roost in the shrubby trees that are resprouting from large stumps that are sprinkled throughout the site. Little islands of Phragmites attract migrant blackbirds (Red-winged Blackbird, European Starling, Brown-headed Cowbird, and Common Grackle) in both fall and spring. A maximum count of 10,000 Red-winged Blackbirds was recorded in 1996. Pied-billed Grebe, Black-crowned Night Heron and Common Moorhen are also found here during migration. Geese are also abundant migrants. Maximums of 8500 Canada Geese in the spring and 6000 Snow Geese in the fall have been recorded. Numerous species of ducks feed here in both migration seasons - species include: Mallard, American Wigeon, American Black Duck, Gadwall, Wood Duck, Blue-winged Teal, Green-winged Teal, and Ring-necked Duck. Small numbers of American Coots, Great Blue Herons, Northern Shovelers and Redheads breed in the marsh. This is one of the few locations in Quebec where the latter species breeds regularly.

Conservation Issues

The site is managed by the Beauharnois-Salaberry Regional Park. Poaching is reported every year despite the fact that a portion of the IBA is within a No Hunting Zone. Furthermore, ATVs, snowmobiles and cross-country skiing in the IBA may lead to the degradation of natural habitats. The growing muskrat population is causing damage to the (protective) dyke and recreational facilities by "tunnelling". For this reason, muskrat control measures were implemented in winter 2013. Nonpoint source pollution from farming activities also threatens the quality of aquatic ecosystems here. Furthermore, the spread of invasive plants, e.g. flowering rush and common water reed, puts considerable pressure on native flora. One of the two dyked pools is being filled with vegetation at an accelerated pace. This is causing a significant reduction in open water areas and may negatively impact some bird populations such as the Least Bittern. Finally, there is a major decline in the number of trees available for the construction of Great Blue Heron nests. Some nests are now found within 50 meters of the bicycle path crossing the marsh. In cooperation with the Société d'observation de la faune ailée, Les Amis de la réserve nationale de faune du Lac-Saint-François is the organization responsible for different conservation and awareness-raising initiatives in the IBA, e.g. guided walks for the Edgar-Hébert High school's students, participation in the Marsh Monitoring Program, and invasive alien species monitoring.

Fish Habitat

A variety of freshwater and diadromous fish coexist in different habitats in the IBA. We found between 70 and 80 species (including historical records) in the area. Several species, such as the northern pike, the yellow perch and the common carp exploit the aquatic vegetation and the floodplains as a spawning ground, a nursery and a feeding ground. Others, such as walleye, freshwater specie with an important economic value in Canada prefer rather to spawn in fast flowing waters. A special feature of this area is the presence of salmonids introduced for sport fishing (brown trout, rainbow tout, and salmons). Salmons were introduced in the Great Lakes and some drift into the St. Lawrence River where they are sometimes caught by anglers. Brown trout and rainbow trout were also stocked in riffles (in the river) for sport fishing.

Several pressures threaten the availability of fish habitats: the creation of embankments, the artificialization of banks, the residential, commercial and industrial development as well as developing the road network, while agricultural, industrial and urban waste deteriorate the water quality. The Eastern sand darter, among others, is very vulnerable to pollution and it is now on the list of endangered species. Among the species listed at risk frequenting the site, we found the lake sturgeon, the channel darter, the bridle shiner, the American eel and some historical records mention the presence of copper redhorse, a fish endemic to Canada designated endangered. In addition, the presence of invasive species such as round goby, threatens the natural dynamics of ecosystems and the water level regulation of the Great Lakes creates risks for the availability of spawning habitats of certain species.

Major species present:
American eel
American shad
Bridle shiner
Brown trout
Channel darter
Common carp
Copper redhorse
Eastern sand darter
Lake sturgeon
Northern pike
Rainbow trout
Smallmouth bass
Yellow perch


The sector is characterized by clear, alkaline and slow flowing water. Theses conditions promote dense plant bed that can cover up to 50% of the water bodies. Submerged plant beds are dominated by wild celery and Eurasian water-milfoil, while emergent marshes are filled with bulrushes, arrowhead and cattails. Several duck species forage in these areas, including the scaup that is fond of wild celery.

Shoreline erosion, whether due to natural factors (wind, freezing and thawing cycles, absence of ice protecting the river banks in spring) or human actions (waves caused by ships), all threaten the riparian habitat. Water level fluctuations affect the ecology of plant and animal species that live there. A significant and prolonged decrease of bank immersion could affect flora by promoting more land species such as shrubs or even trees. In addition, the spread of invasive species exerts considerable pressures on the native flora of these habitats.

Major species present :
American bulrush
Broad-leafed arrowhead
Broad-leafed cattail
Eurasian water-milfoil – invasive species
Great bulrush
Narrow leaf cattail
Sessilefruit arrowhead
Wild celery

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status
Rusty Blackbird
Number Year Season
30 - 602017Spring
Least Bittern
Number Year Season