The Carden Plain is located in central Ontario to the east of Lake Simcoe. It is bordered to the north by the southern edge of the Canadian shield (extensive forests, lakes, and wetlands), and to the south, much of the landscape is fragmented and utilized for agriculture. The plain consists of grassland and alvar interspersed with scattered cropland, woodlots and some large wetlands (most are recognized as being provincially significant). The limestone alvars have thin soils and sparse vegetation, with the groundwater system being poorly developed (most precipitation remains on the surface and subsequently evaporates creating flood/drought conditions). This harsh environment supports several specialized plants with western or prairie affinities, many of which have been identified as provincially and/or nationally rare (e.g., Astragalus neglectus, Draba reptans, Sporobolus heterolepis). The area is lightly populated, with most of the human habitation being concentrated in the cottage areas around Canal Lake and Lake Dalrymple.
The Carden Plain is one of the few areas in eastern Canada that still supports nesting Loggerhead Shrikes (ssp. migrans designated as nationally endangered). In 1992, seven pairs and 4 singles were recorded, with this number declining steadily to only one pair and one single in 1997. In 1998, the population rebounded to five pairs, and five singles. Henslows Sparrows (designated nationally endangered) have also been reported as possible nesters, but breeding has not been confirmed. Several other nationally threatened species nest in the area, including Red-shouldered Hawk, Short-eared Owl, Least Bittern, Red-headed Woodpecker, and Yellow Rail.
The Carden Plain also supports significant breeding concentrations of grassland birds. A 1996 study estimated 800 1000 pairs of Bobolinks, 500 600 pairs of Eastern Meadowlarks, 300 400 pairs of Upland Sandpipers and Eastern Bluebirds, and 200 300 pairs of Grasshopper Sparrows.
BirdLife International (2020) Important Bird Areas factsheet: Carden Plain. Downloaded from http://www.birdlife.org on 28/11/2020.