Least Bittern
(Ixobrychus exilis)


Picture of bird
© John Reaume
For additional photos and vocalizations, visit Dendroica. (Link opens in a new window.)

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.


Listing of the main designations for the species
DesignationStatusDateSubspecies, population
COSEWIC (Canada)Threatened2009 
SARA (Canada)Threatened2003 
IUCN (Global)Least Concern2012 
Wild Species (Canada)At Risk2010 
Bird Conservation Region StrategyPriority Species2013 

Population status

Geographic areaStatusReliability
CanadaModerate DecreaseLow

Population estimate

Canada1,000 - 10,000 breeding birds

Distribution maps


Migration strategy, occurrence

Short-distance migrant

Responsibility for conservation of world population


Conservation and management

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.


Bird conservation region strategies

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:

  • conservation concerns (i.e., species vulnerable due to population size, distribution, population trend, abundance, or threats)
  • stewardship responsibilities (i.e., species that typify the regional avifauna or have a large proportion of their range or population in the sub-region)
  • management concerns (i.e., species that require ongoing management because of their socio-economic importance as game species, or because of their impacts on other species or habitats)
  • other concerns (i.e., species deemed a priority by regional experts for other reasons than those listed above or because they are listed as species at risk or concern at the provincial level)

Select any of the sub-regions below to view the BCR strategy for additional details.

BCRs, marine biogeographic units, and sub-regions in which the species is listed as a priority
RegionSub-region and priority type
Atlantic Northern ForestsAtlantic Northern Forests, sub-region and priority type: Atlantic Region - New Brunswick
Atlantic Northern ForestsAtlantic Northern Forests, sub-region and priority type: Quebec Region
Boreal Hardwood TransitionBoreal Hardwood Transition, sub-region and priority type: Ontario Region
Lower Great Lakes/St. Lawrence PlainLower Great Lakes/St. Lawrence Plain, sub-region and priority type: Ontario Region
Lower Great Lakes/St. Lawrence PlainLower Great Lakes/St. Lawrence Plain, sub-region and priority type: Quebec Region
Prairie PotholesPrairie Potholes, sub-region and priority type: Prairie and Northern Region