Port Colborne, Ontario
Port Colborne is located on the northern shore of Lake Erie at the eastern end of the Lake. The site is comprised of colonies at two locations: on a breakwater, which is located 1 km offshore, to the southwest of the mouth of the Welland Canal; and on a landfill at the southernmost tip of the Algoma Property on the immediate east side of the mouth of the Welland canal.
Construction of the breakwater started in 1901 in association with the operation of the third Welland Canal (part of the St. Lawrence Seaway System). In 1903, a lighthouse was built at the east end of the structure, and a helipad was constructed close by in 1987. The breakwater is about 700 m long east-west, with a south arm about 400 m long. A pile of loosely scattered limestone boulders and gravel occurs at the intersection of the two arms. The mainland site is a human-created landfill stretching along the east side of the Welland Canal. It has a rock base, and a thin layer of organic material that supports grass and other herbaceous plants.
Large numbers of Common Terns and Ring-billed Gulls nest at these two colonies. The Common Terns are restricted to the Breakwater site, while the Ring-billed Gulls nest at both locations. A peak of 1,311 pairs of Common Terns was recorded at the breakwater site in 1987; however, a major storm on 5 December 1987 washed all of the nesting material into the lake, leaving behind bare concrete slabs. Rock and gravel material was hand-shoveled from the rock pile and redistributed along the east arm in subsequent years. The numbers of nesting terns dropped slightly after this event, with the long term average (over 14 years) being about 1,000 pairs (over 2% of the estimated North American breeding population).
The Ring-billed Gulls nest primarily on the mainland site. In 1990, 43,590 pairs were estimated there, along with 2,500 pairs on the breakwater. This may represent as much as 5% of the estimated North American breeding population.
In addition to Ring-billed Gulls and Common Terns, about 175 pairs of Herring Gulls nest at the colonies, and in 1997 a pair of Great Black-backed Gulls nested there for the first time.
The Common Tern and Ring-billed Gull colonies at Port Colborne are the subject of a long term study being undertaken by researchers from Brock University in St. Catharines. The main threats to the colonies are human disturbance and substrate alteration. In addition, the Common Terns are especially susceptible to pressure from the Ring-billed Gulls; in particular the occupation of suitable nesting habitat, as well as egg and chick predation. Despite intense management, the Ring-billed Gulls appear to be gaining control of the Common Tern nesting areas. The number of nesting tern pairs was below 600 (21 May 1998) for the first time since the late 1970s. Management of the breakwater colony is being supervised by researchers from Brock University.Catégories ZICO Habitats Usages Menaces Potencielles ou Existantes Status de Protection
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