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An elusive marsh bird, the Least Bittern breeds primarily in southern Ontario but also in southern Manitoba, Quebec and the Maritimes. The Great Lakes Marsh Monitoring Program and Atlas of the Breeding Birds of Ontario suggest a decrease across much of the species' range, though the reliability of this assessment is considered low. The Least Bittern was designated as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1988 and 1999, and re-classified as Threatened in 2001 and 2009 because of its small population size and probable decline (COSEWIC 2009c). This species has been identified as a priority for conservation and/or stewardship in one or more Bird Conservation Region Strategies in Canada.
Although its secretive nature and poor detectability have restricted knowledge of many aspects of Least Bittern ecology, wetland habitat loss is likely the primary driver of population declines (Poole et al. 2009). With a preference for large shallow marshes with emergent vegetation, this species has suffered a rapid reduction in possible breeding sites in the core of its range in southern Ontario, where over 90% of original wetlands have been destroyed or altered by agricultural development (COSEWIC 2009c). Fragmentation and contamination of remaining wetlands and anthropogenic disturbance to breeding birds may limit the Least Bittern's recovery from currently low abundance, while monitoring and conservation efforts are complicated by its discontinuous breeding distribution (Poole et al. 2009, COSEWIC 2009c). The spread of invasive plants that crowd out native emergent vegetation (Wilcox et al. 2003, Lavoie et al. 2003) and unnatural water level fluctuations in impounded wetlands (e.g., Jobin et al. 2011) may lead to changes in composition of marsh vegetation and degradation of nesting habitat. For information on the legal status of this species under the Species at Risk Act (SARA) and to view the proposed Recovery Strategy, see the SARA Registry.
Environment and Climate Change Canada and partners have developed Bird Conservation Region Strategies in each of Canada’s Bird Conservation Regions (BCRs). In these strategies, selected species are identified as priorities for one or more of the following reasons:
Select any of the sub-regions below to view the BCR strategy for additional details.
