Carden Alvar (ON040)

Carden Alvar (ON040)

Kirkfield, Ontario

Site Description

The Carden Alvar 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 area 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.

Birds

The Carden Alvar 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 Alvar also supports significant breeding concentrations of grassland birds. A 1996 study estimated 800 to 1000 pairs of Bobolinks, 500 to 600 pairs of Eastern Meadowlarks, 300 to 400 pairs of Upland Sandpipers and Eastern Bluebirds, and 200 to 300 pairs of Grasshopper Sparrows.

Conservation Issues

The primary threats to the area are general loss of habitat due to changes in land use, natural succession, and expansion of quarrying. Collisions with motor vehicles, pesticide use, and the use of dust suppressants on dirt roads (in core breeding areas) also seem to be having a negative effect on the shrike populations.

The National Recovery Plan for Loggerhead Shrikes (prepared in 1993) identified the Carden Alvar as one of three sites that should be intensively monitored for nesting Loggerhead Shrikes. The Couchiching Conservancy conducts an extensive Volunteer Shrike Survey in May and then monitors the sites throughout the remainder of the breeding season. A landowner contact and extension program was also initiated in 1997. The Long Point Bird Observatory (now Bird Studies Canada) developed the Landowners Resource Kit for Endangered Loggerhead Shrikes, a kit designed to provide accurate, practical information about the species, as well as activities that can be conducted to help conserve it.

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status

• Golden-winged Warbler200 (max.)
• Loggerhead Shrike20 (max.)
• Henslow's Sparrow3 (max.)
• Kirtland's Warbler1 (max.)