Great Blue Heron
(Ardea herodias)


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

A species of wetland habitat, the Great Blue Heron is widely distributed in Canada. Results from the Breeding Bird Survey suggest that abundance has decreased by 30% since 1970, although regional trends vary. The fannini subspecies, resident only in coastal British Columbia, has shown a large decrease since 1970. The subspecies was designated as Special Concern by the Committee on the Status of Endangered Wildlife in Canada in 1997 and again in 2008 because of its small numbers, declining productivity, and uncertain trends (COSEWIC 2008g); it was listed as such under the Species at Risk Act in 2010. 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)Special Concern2008Great Blue Heron fannini subspecies
SARA (Canada)Special Concern2010Great Blue Heron fannini subspecies
IUCN (Global)Least concern2018 
Wild Species (Canada)Secure2015 
Bird Conservation Region StrategyPriority Species2013 

Population status

Geographic area or populationPopulation change relative to ~1970ReliabilityStatus in relation to goal
CanadaModerate DecreaseMediumBelow Acceptable Level
Great Blue Heron fannini subspeciesLarge DecreaseHighBelow Acceptable Level

Population estimate

Geographic area or populationPopulation estimate
Canada10,000 - 25,000 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-March and early May and ends between early August and late August, depending on the region. Before or after this period, the probability of an active nest is lower.

Conservation and management

Great Blue Herons are vulnerable to wetland habitat loss and degradation throughout their range; disturbance at nesting sites and destruction of marshes likely continue to threaten breeding colonies (COSEWIC 2008g). However, recent declines in central Canada may be most closely associated with changing amphibian populations, a major food source, rather than a direct consequence of habitat loss (Naylor 2007). The species is tracked as an indicator of trends in contaminants, and levels of regulated contaminants such as DDT and PCBs have declined significantly since the 1990s in some portions of the range (Champoux and Boily 2017). A growing population of Bald Eagles in British Columbia may be disturbing nesting fannini herons and usurping their nesting colonies, forcing the herons to relocate (e.g., Myrvold and Kennedy 2018), as well as increasing predation pressure on the population (Environment Canada 2016e). Finally, colony sites are limited to areas within reach for foraging areas (Knight et al. 2016), so increasing urban development in those areas may further increase pressure on these birds.


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
Great BasinGreat Basin, sub-region and priority type: Pacific and Yukon -- Other
Lower Great Lakes/St. Lawrence PlainLower Great Lakes/St. Lawrence Plain, sub-region and priority type: Ontario -- Conservation
Northern Pacific RainforestNorthern Pacific Rainforest, sub-region and priority type: Pacific and Yukon -- Other
Northern RockiesNorthern Rockies, sub-region and priority type: Pacific and Yukon -- Other
Prairie PotholesPrairie Potholes, sub-region and priority type: Prairie and Northern -- Other