IBA Luther Marsh
Grand Valley, Ontario
Site Summary
ON059 Latitude
43.944° N
80.431° W
490 m
105.32 km²
mixed woods (temperate), freshwater lake, freshwater marsh, bog, abandoned & fallow farmland/disturbed ground
Land Use:
Agriculture, Nature conservation and research, Rangeland/pastureland, Tourism/recreation, Water management
Potential or ongoing Threats:
Agricultural pollution/pesticides, Disturbance, Dredging/canalization, Dykes/dam/barrages, Hunting, Recreation/tourism
IBA Criteria: Nationally Significant: Threatened Species, Waterfowl Concentrations
Conservation status: Conservation Authority (owned by), IBA Conservation Plan written/being written
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Site Description
Luther Marsh is located in central southwestern Ontario, about 20 km west of the town of Orangeville. The marsh was formed by damming one of the Grand Rivers upper tributaries. Within the site, there are three main areas of interest: the actual lake and various islands and bogs therein; a forest with northern characteristics; and Wylde Lake, which is a raised bog of boreal character (sphagnum moss and scattered Tamaracks) southeast of the main lake. In the fall, the lake is drawn down and large areas of mud and floating algae appear, which are very productive for migratory shorebirds.
Luther Marsh provides significant habitat for a variety of wetland bird species. Least Bittern (designated as nationally vulnerable) nest at this site, with at least 10 pairs being present (about 1% of the estimated national population). Black Terns also nest at this site with about 20 to 25 pairs being present in the 1990s. Historically, much larger numbers nested here, with 100s of pairs being reported in the 1960s and 1970s. Other waterbirds of note include Common Loon (1 2 pairs), Red-necked Grebe (last breeding record 1985), Wilsons Phalarope (3 5 pairs in 1992), Osprey (3 4 pairs annually), Great Egret (1 pair occasionally), Great Blue Heron (about 80 pairs). On occasion, relatively large numbers of Great Egrets concentrate at this site during the early fall (29 in September 1993).

The site is also significant for waterfowl. At least 15 species of ducks nest at Luther Marsh. In order of abundance, these species include Mallard, Gadwall, American Wigeon, Blue-winged Teal, Lesser Scaup, Redhead, Ring-necked Duck, American Black Duck, Ruddy Duck, Green-winged Teal, Northern Pintail, Wood Duck, Hooded Merganser, Canvasback, and Northern Shoveler. As many as 900 pairs of the above mentioned ducks have been estimated to breed at Luther Marsh during a given season. During the fall migration, dabbling ducks such as Mallards, American Black Ducks, American Wigeon and teal concentrate at this site, with as many as 15,000 being regularly reported in the 1970s. More recently, peak numbers during fall migration have been closer to 10,000.

Several landbird species of conservation interest also nest at this site. The bogs at the Wylde Lake area support one of Ontarios southern most breeding locations for Lincolns Sparrow; Short-eared Owls (nationally vulnerable) have also nested in the sedge and grass areas throughout the site; and there are breeding records for LeContes Sparrow, and Henslows Sparrows. Henslows Sparrows have been designated as nationally endangered, and they are also recognized as globally near-threatened. During the breeding season, Henslows Sparrows were located in the Luther Marsh area from the 1930s through to the mid-1980s. However, there have been no breeding records over the last ten years.

IBA Criteria
SpeciesT | A | I Links Date Season Number G C N
Henslow's Sparrow 1935 - 1985 SU 2
Least Bittern 1901 OT 20
Northern Bobwhite 2003 SP 4
Northern Bobwhite 2001 SU 4
Rusty Blackbird 2014 - 2016 FA 50 - 800
Rusty Blackbird 2014 SP 1,200
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
Luther Marsh was developed by the Grand River Conservation Authority as water management scheme to augment the flow of the Grand River during the summer. It still managed for this purpose, as well as for general year-round recreational use, and in the fall, hunting opportunities. In portions of Luther Marsh, there are localized threats from agricultural run-off, and some loss of wetlands, but for the most part, the site is protected as a conservation area.

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