Dundas Valley and Dundas Marsh

Year of compilation: 2001

Site description
The Dundas Valley is an extensive natural area located in southern Ontario along the Niagara Escarpment. Immediately to the east is the town of Dundas and Dundas Marsh (also called Cootes Paradise). The Spring Creek valley forms a narrow, natural corridor joining Dundas Valley to Dundas Marsh. Most of the Dundas Valley area is comprised of relatively undisturbed deciduous and mixed upland forest. The topography is quite varied, being comprised of rolling hills, deeply incised stream courses, and steep valley walls, with local relief of 30 metres or more being common. Dundas Marsh is located at the western end of Hamilton Harbour, and is a shallow flooded basin of open water and marsh joined to Hamilton Harbour by the Desjardins Canal. The shallow open water pond is dominated by water lilies and Sago Pondweed while the shoreline is dominated by cattail and Manna Grass. The surrounding terrain consists of rolling hills and ravines, covered woods and successional communities.

Also included in the site are Spencer Creek Gorge and Tiffany Falls. The flora and fauna of the valley and marsh have been well studied with an exceptional concentration of significant flora and fauna being present. Over 580 species of vascular plants have been recorded for the valley (17 nationally and/or provincially rare), and over 800 species for the marsh (25 of which are nationally rare).

Key biodiversity
The Dundas Valley contains a nationally significant community of forest birds. Breeding evidence for at least five nationally vulnerable, threatened or endangered species has been recorded. Two of these threatened species are regularly present in nationally significant numbers (i.e., greater than 1% of their national population). These species are the Hooded Warbler (two to four pairs annually), and Louisiana Waterthrush (two to four pairs annually). Cerulean Warbler (nationally vulnerable) is also present within the valley, but not in nationally significant numbers. Yellow-breasted Chat (nationally vulnerable) and Acadian Flycatcher (nationally endangered) have also been recorded within the valley, but only on an irregular basis.

During recent years, about 100 species of breeding birds have been recorded within the valley (one of the more species rich areas in southern Ontario). A relatively large proportion of these are neotropical migrants, of which the more abundant species are Red-eyed Vireo, Wood Thrush, Eastern Wood-Peewee, Ovenbird, and Scarlet Tanager. Of additional ornithological interest is the presence of both hybrids of Blue-winged and Golden-winged Warblers.

Dundas Marsh is an important area for migrating waterfowl, shorebirds, herons, raptors, gulls, terns, and songbirds. There is confirmed breeding evidence for three species at risk in Canada: Least Bittern (vulnerable), Cerulean Warbler (vulnerable) and Prothonotary Warbler (endangered), the latter having nested annually for the last five or so years, and has nested here regularly, but not annually, since at least the 1950s. In addition, Yellow-breasted Chat (vulnerable) possibly bred in 1974, as might a pair of King Rails (endangered) in the 1960s. Other breeding species include Double-crested Cormorant (121 nests in 1997), Blue-winged Teal, Common Moorhen, Yellow-billed Cuckoo, Whip-poor-will, Eastern Bluebird, Tufted Titmouse, Carolina Wren, Black-throated Green Warbler and Orchard Oriole.

Conservation responses/actions for key biodiversity
The significance of the Dundas Valley (and/or various portions of it) has been recognized through a variety of programs or designations. At the municipal level, it is identified as an Environmentally Sensitive Area in the Hamilton-Wentworth Regional Official Plan; at the provincial level, it is identified as both a Life Science and Earth Science Area of Natural and Scientific Interest, and also as part of the Niagara Escarpment Planning Area; and at the international level it is recognized as part of the Niagara Escarpment World Biosphere Site, and was examined under the International Biological Programme (IBP).

Even with the recognition provided by these programs, the breeding bird community within the valley is under considerable and increasing pressure. The valley is located on the northwest edge of Dundas-Ancaster-Hamilton urban area, and as such is experiencing sustained pressure from development and other land uses. All of the nationally significant bird species present at this site, as well as many of the other neotropical migrants, are susceptible to development related pressures, especially increases in habitat- generalist nest predators such as squirrels, raccoons, opossums, skunks and cats. From a landscape perspective, the valley has more extensive forests and more forest interior than most areas in southwestern Ontario and is relatively well connected to surrounding natural areas by naturally-vegetated corridors.

The aquatic and wetland systems of Dundas Marsh have been adversely impacted by the cumulative effects of off-site manmade changes such as the moderation of fluctuations in the water level in Lake Ontario and increased sedimentation and poor water quality due to rapid urbanization of upstream areas. The extent and quality of the aquatic and wetland vegetation in this area has undergone a dramatic decline during this century, due to excessive sedimentation, excessive turbidity, the spread of non-native species, and feeding and spawning activities by carp (a fish-way has been built to help control the carp, however, and thus restore the native vegetation). Most of the area is public-owned as part of the Royal Botanical Gardens and is managed as a wildlife reserve and conservation education centre.

Recommended citation
BirdLife International (2022) Important Bird Areas factsheet: Dundas Valley and Dundas Marsh. Downloaded from on 03/12/2022.