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 the southern parts of Ontario, Manitoba, and Quebec, as well as the Maritimes. The small amount of information available from this species' range in Canada suggests that it has shown little overall change since 1970. However, 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.


Main designations for the species
DesignationStatusDateSubspecies, population
COSEWIC (Canada)Threatened2009 
SARA (Canada)Threatened2003 
IUCN (Global)Least concern2018 
Wild Species (Canada)Vulnerable2015 
Bird Conservation Region StrategyPriority Species2013 

Population status

Geographic area or populationPopulation change relative to ~1970ReliabilityStatus in relation to goal
CanadaLittle ChangeLowAt an Acceptable Level

Population estimate

Geographic area or populationPopulation estimate
Canada1,000 - 10,000 breeding birds

Distribution maps


Migration strategy, occurrence

Short-distance migrant

Responsibility for conservation

Geographic areaResponsibility based on % of global population

General nesting period in Canada

Nesting period starts between mid-May and late May and ends between late July and early August, depending on the region. Before or after this period, the probability of an active nest is lower.

Conservation and management

The Least Bittern is secretive, so many aspects of its breeding ecology are poorly known. However, recent survey efforts have greatly increased the knowledge of its distribution and habitat use in Canada (Jobin et al. 2013, OMNRF 2016). Wetland habitat loss is likely the primary driver of historical 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, 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 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, NB -- Other
Atlantic Northern ForestsAtlantic Northern Forests, sub-region and priority type: Quebec -- Other
Boreal Hardwood TransitionBoreal Hardwood Transition, sub-region and priority type: Ontario and Manitoba -- Conservation
Lower Great Lakes/St. Lawrence PlainLower Great Lakes/St. Lawrence Plain, sub-region and priority type: Ontario -- Conservation
Lower Great Lakes/St. Lawrence PlainLower Great Lakes/St. Lawrence Plain, sub-region and priority type: Quebec -- Other
Prairie PotholesPrairie Potholes, sub-region and priority type: Prairie and Northern -- Other