IBA Île Deslauriers
Varennes, Québec
Site Summary
QC126 Latitude
45.713° N
73.441° W
20 m
0.96 km²
native grassland, abandoned & fallow farmland/disturbed ground
Land Use:
Potential or ongoing Threats:
Disturbance, Interactions with native species/disease
IBA Criteria: Globally Significant: Congregatory Species, Colonial Waterbirds/Seabird Concentrations
Conservation status:
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Site Description
Île Deslauriers is part of the Varennes Archipelago in the St. Lawrence River, just east of Montréal and directly north of the town of Varennes. The western part of the island contains mounds of sediment from dredging of the river. In spring, about 30% of the island becomes submerged.

Vegetation on the island consists of short grasses, and Black Mustard and dandelions grow on the spoil piles. Aquatic vegetation is composed of arrowhead, Sago Pondweed and Spiked Water-milfoil.

An extremely large Ring-billed Gull colony is located on Île Deslauriers. Over the past two decades, the colony has substantially increased in size. At last count in 2000, 51,667 pairs (5% of the global Ring-billed Gull population) nested on the island, which makes this colony the largest in Québec as well as one of the largest in Canada, and represents over 5% of the world's population.

A population of Black-crowned Night-Herons has recently become established on the island and has shown a large increase in recent years. In 1994, 28 pairs nested on the island, and in 1997 there were 49 pairs. Compared to other nearby islands, Île Deslauriers hosts large numbers of breeding Gadwall and other waterfowl species. A Bank Swallow colony is also located on the northeast part of the island.

IBA Criteria
SpeciesT | A | I Number Year Month Day Season A4i/ii B4i/ii/iii A1 B1 C1 Reference
Ring-billed Gull 94,402 1991 SU 25,500 25,500 BIOMQ 1999
Ring-billed Gull 94,402 1991 5 16 SP 25,500 25,500 eBird Canada
Ring-billed Gull 97,582 1994 SU 25,500 25,500 BIOMQ 1999
Ring-billed Gull 97,582 1994 5 18 SP 25,500 25,500 eBird Canada
Ring-billed Gull 97,534 1997 SU 25,500 25,500 BIOMQ 1999
Ring-billed Gull 97,534 1997 5 14 SP 25,500 25,500 eBird Canada
Ring-billed Gull 103,334 2000 SU 25,500 25,500
Ring-billed Gull 103,354 2000 5 17 SP 25,500 25,500 eBird Canada
Ring-billed Gull 101,620 2003 5 15 SP 25,500 25,500 eBird Canada
Ring-billed Gull 102,000 2006 4 30 SP 25,500 25,500 eBird Canada
Ring-billed Gull 95,778 2009 5 13 SP 25,500 25,500 eBird Canada
Ring-billed Gull 40,000 2017 5 17 SP 25,500 25,500 eBird Canada
Ring-billed Gull 50,000 2017 6 26 SU 25,500 25,500 eBird Canada
Ring-billed Gull 25,000 2017 7 12 SU 25,500 25,500 eBird Canada
Ring-billed Gull 25,000 2018 6 20 SU 25,500 25,500 eBird Canada
Ring-billed Gull 30,000 2018 6 22 SU 25,500 25,500 eBird Canada
Ring-billed Gull 25,000 2019 5 8 SP 25,500 25,500 eBird Canada
Ring-billed Gull 30,000 2020 5 6 SP 25,500 25,500 eBird Canada
Note: species shown in bold indicate that the maximum number exceeds at least one of the IBA thresholds (sub-regional, regional or global). The site may still not qualify for that level of IBA if the maximum number reflects an exceptional or historical occurrence.
Conservation Issues
Accidental or purposeful human disturbance and red fox predation could both potentially affect the health of this colony.
Fish Habitat
This zone is rich in aquatic vegetation beds and wetlands in the island area. Its is a area presenting a great potential for spawning for many species of fish, including the northern pike, the walleye black, the brown bullhead, the smallmouth bass and the yellow perch. Some other species, such as lake sturgeon, use spawning ground located in fast flowing waters. More than 53 species are found in this area. Various species are targeted by commercial and sport fishing, including the American shad, which attracts many anglers during the spawning period in late May and early June. The region is also home to the copper redhorse, endangered specie endemic to Québec; the lake sturgeon which is considered as threatened in Québec; and the American eel, a species of least concern.

The destruction of spawning and aquatic habitats in wetlands threatens the reproductive success of the ichthyofauna. The cases are multiple and include artificialization of the shoreline, the agriculture practiced on islands, the presence of resorts, the recreational and commercial boating (bank erosion by waves). In addition, some species, such as walleye, are affected by the decrease in water quality, mainly created by industrial activities in the region as well as municipal and agricultural pollution. The rainbow smelt, once abundant in this area, has disappeared because of the destruction of its spawning sites in small tributaries.

Major species present:
American eel
American shad
Brown bullhead
Copper redhorse
Lake sturgeon
Northern pike
Spottail shiner
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

The IBA Program is an international conservation initiative coordinated by BirdLife International. The Canadian co-partners for the IBA Program are Birds Canada and Nature Canada.
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