The Spencer Gorge study area encompasses a south-facing segment of the Niagara Escarpment overlooking the town of Dundas. The central feature of this area is Spencer Gorge, a ‘y’-shaped bedrock gorge which is a distinctive landform as it provides a near-complete section of the bedrock formations of the southern Niagara Escarpment. The biological communities in the gorge are also considered high-quality, representative examples of escarpment valley vegetation pattern, which provide habitat for many rare and uncommon species.
Ontario Ministry of Natural Resources Designation:
• Provincial Life Science ANSI (Area of Natural and Scientific Interest)
• Provincial Earth Science ANSI (Area of Natural and Scientific Interest)
City of Hamilton Environmentally Significant Area (ESA) Criteria:
• Significant Earth Science Feature
Spencer Gorge is located at the junction of three branches of the
Spencer Creek system. Logie’s Creek (also known as East Spencer Creek)
drains into the eastern head of the gorge and forms Tew’s Falls. The
main trunk of Spencer Creek flows into the western arm at Webster’s
Falls. The third unnamed tributary forms a small waterfall on the west
side of the western arm. This study area also includes the adjacent
south-facing sections of the escarpment face and a second minor
escarpment valley occupied by Sydenham Creek. Elevations in this area
range from 120 to 235 m and slopes are generally very steep.
The geomorphology of the 1 km long, ‘y’-shaped gorge is unique to the Niagara Escarpment and provides an excellent example of the process of waterfall recession. The excellent bedrock exposures in this study area provide an exceptional record of the local sedimentary environment during the Upper Ordovician and Lower and Middle Silurian periods, roughly 440 to 415 million years ago. The town of Dundas is built on a gently-sloping gravel deposit, called the Dundas Alluvial Fan, which extends southeast from the mouth of the Spencer Gorge.
The Spencer Gorge encompasses a relatively mature and undisturbed array of escarpment-associated plant communities, and encompasses one of the few south-facing segments along the Niagara Escarpment corridor through the City of Hamilton. Although the communities along this south face are variously disturbed due to the proximity of the CN railway and roadcuts, the relatively warm and dry climate along this slope supports a regionally rare habitat situation. Escarpment-associated communities include dolostone cliffs, extensive talus slopes, scree valley slopes, and dry rim forests. Red oak (Quercus rubra) and white oak (Quercus alba) dominate the mature escarpment rim community; occasional open rims on the valley crest sustain small prairie patches. Stunted white cedars dominate the exposed cliff faces.
Flora and Fauna Summary
Nature Counts botanists recorded 269 species in 2001 and 2002. Of these, 42 (16%) are introduced species, 13 are Carolinian species, 13 are locally uncommon and 13 are locally rare. Moreover, Downy Fox Glove (Aureolaria virginica), Hairy Buttercup (Ranunculus hispidus var. hispidus), Sharp-leaved Goldenrod (Solidago arguta var. arguta) and Rue-anemone (Thalictrum thalictroides) are locally and provincially rare, while Red Mulberry (Morus rubra) is locally, provincially and nationally rare. During field surveys conducted between 1962 and 2000, 521 species were recorded including 47 significant species, 132 (25%) introduced species and 18 Carolinian species.
In 1989 and 1991, 16 species were recorded, including one locally uncommon species and a COSEWIC special concern species, the Monarch (Danaus plexippus).
Spencer Creek flows over the Niagara Escarpment and falls steeply through a series of step pools until it is diverted through a culvert under the CN rail line. Groundwater is added through the gorge and the stream is a coldwater system in this area. Fish were assessed here between 1986 and 1997. In total, 15 species were collected, but only seven species have been recorded since 1990, including two that are uncommon in the City of Hamilton. Brown bullhead (Ameiurus nebulosus) and pumpkinseed (Lepomis gibbosus) were found in the 1990s, but not recorded before that decade.
Six species were recorded from 1987 to 1990 including two locally uncommon species and Eastern Milk Snake (Lampropeltis triangulum triangulum), a COSEWIC special concern species.
Nature Counts surveyors recorded 18 species during one field visit in 2001. Of these, five are locally uncommon and one, Yellow-rumped Warbler (Dendroica coronata), is locally rare. During 1991, 19 species were recorded including three locally uncommon species and Louisiana Waterthrush (Seiurus motacilla), a locally, provincially and nationally significant species.
The Nature Counts project conducted small mammal trapping in 2001 and 2002, as well as bat mist netting in 2002. Ten species were recorded, seven of which are new records for the area.
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