Île Blanche (QC048)

Île Blanche (QC048)

Rivière-du-Loup, Québec

Site Description

Île Blanche is an island that is situated 10.5 km from Rivière-du-Loup, and 2.4 km off the northeast point of Île aux Lièvres, approximately midstream in the St. Lawrence estuary, Québec. Île Blanche is a low-lying shale island that supports 4.5 ha of vegetation. A mature forest of White Spruce and White Birch, which covers most of the island, has been thinned out considerably through the death of many trees. This was caused by both great numbers of tree-nesting birds and by small scale lumbering operations in the early 1960's. The forest is encircled by a narrow belt of grass and shrubs. At low tide, the island is surrounded by extensive flats composed of sedimentary rocks dotted with tidal pools. The mean tidal amplitude is about 3.5m and the mean annual temperature is 3°C.

Birds

A very large colony of eiders is found on Île Blanche. Between 1965 and 2000, the island was surveyed for nesting Common Eider on twenty-two occasions. An average of 2,665 nests was recorded, representing about 1% of the North American breeding population, or about 3% of the Atlantic (ssp. dresseri) population of this species. The highest number recorded was 4,832 nests in 1984 and the lowest was 1,332 nests in 1995. The density of Common Eider nests is quite high at 844 nests per hectare.

In addition to sea ducks, this site is important during the fall for migrant shorebirds; a total of 7,020 birds have been recorded at this site. Purple Sandpiper has been seen in numbers as high as 180 birds, which is almost 2% of the North American population.

Tree-nesting colonial waterbirds such as herons and cormorants formerly nested here, but no longer do so as the trees can no longer support nests. In 1966, 130 Black-crowned Night-Heron nests were observed. In just one year, however, the colony was reduced to 80 nests, and by 1986 there were no breeding night-herons. In 1967, 180 Great Blue Heron nests were recorded, but in 1999 none were present. Between 700 to 1,640 Double-crested Cormorant nests were reported between the years 1965 and 1979, but in the 1980s and 1990s the number decreased steadily. No cormorants bred on the island in 1999.

Five surveys of gulls between 1965 and 1990 revealed an average of 695 pairs of Herring Gull and 53 pairs of Great Black-backed Gulls.

Conservation Issues

In 1964 and 1966, outbreaks of avian cholera occurred amongst nesting eiders on Île Blanche – an estimated 1000 adult females died in 1964 and 700 in 1966 (out of about 4000 females present per year). None of the other species breeding on the island were affected by this disease. The high density of birds found at this site increases the likelihood of this disease.

The high numbers of birds at this site attract many curious on-lookers in boats during the spring. Such activity sometimes unintentionally disturbs the birds. There is the potential for oil spills to occur from numerous freighters passing by the island.

Fish Habitat

The landscape of the are is made out of Spartina marsh, eelgrass beds, rocky shores and gravel or pebbles beaches. Some rivers are hosting rainbow smelt spawning runs (the south shore population of the St. Lawrence middle estuary). At the beginning of the summer, it is possbile to observe capelin rolling on the beaches during spawning. The downstream migration of American eel toward their breeding sites in the Atlantic, which takes place in the fall, allows the capture of migraing adults using fishing weirs. Two other species commercially exploited are also roaming in the open waters of the estuary: the Atlantic sturgeon and Atlantic herring.

Loss of fish habitat remains a major problem in the region. The dikes, for example, reduce the number of spawning habitats, while agricultural along the coast, the residential development and the presence of resorts together with coastal erosion are resulting in the destruction of several riparian ecosystems.


Major species present:
American eel
American shad
Atlantic herring
Atlantic sturgeon
Capelin
Rainbow smelt (population of south shore of the St. Lawrence middle estuary)
Stickleback

Plants

Rocky islands are composed of schist and quartzite. Despite the unfavorable conditions for settlement, some plant species are able to grow there. On the windward side, we find mainly mosses and low-lying plants such as juniper and cranberries. Areas more sheltered allow spruce to built small woodlands. In the portion swept by the tides, algae colonize the bedrock.

The geographical barrier created by the St. Lawrence River provides the IBA a kind of natural protection, a protection often enhanced by legal protection. However, water pollution and the risks of oil spills remain a source of concern for the protection of the flora and fauna of this area.


Major species present :
Cranberries
Creeping juniper
Spruces

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status

• Purple Sandpiper458 (max.)
• Black Guillemot2,240 (max.)
• Barrow's Goldeneye50 (max.)