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.
BirdLife International (2020) Important Bird Areas factsheet: Luther Marsh. Downloaded from http://www.birdlife.org on 27/09/2020.