BC Conservation Data Centre: Conservation Status Report
Ardea herodias
Great Blue Heron
| Scientific Name: | Ardea herodias |
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| English Name: | Great Blue Heron |
| Provincial Status Summary | |
| Status: | S3 |
| Date Status Assigned: | June 30, 1998 |
| Date Last Reviewed: | March 05, 2015 |
| Reasons: | A relatively widespread species with a number of colonies on the coast and in the southern interior. However, there are fewer than 30 active colonies with more than 20 pairs of breeding birds, and the species is vulnerable to pollution, disturbance and habitat loss. |
| Range | |
| Range Extent: | FG = 20,000-2,500,000 square km |
| Range Extent Comments: | Breeding on the coast is primarily in the Georgia Depression. In the southern interior breeding occurs from the Okanagan Valley north sporadically to Williams Lake, and in the west Kootenays north to Golden. Distribution of non-breeding birds is more widespread. The major winter concentration in British Columbia is on the Fraser River delta, and the major wintering area in the interior is in the Okanagan Valley (Campbell et al. 1990a). |
| Occurrences & Population | |
| Number of Occurrences: | C = 21 - 80 |
| Comments: | On the south coast (around the Strait of Georgia and Strait of Juan de Fuca) there are only 15 known breeding colonies of A. h. fannini that contain more than 20 pairs each (Moul 1998). Herons are sparse on the north coast, and none of the few known colonies exceed 20 pairs (Butler pers. comm.). In the interior there are nine colonies of A. h. herodias with more than 20 pairs each (Campbell et al. 1990a). |
| Number of Occurrences with Good Viability / Ecological Integrity: | Rank Factor not assessed |
| Number of Occurrences Appropriately Protected & Managed: | BC = 1 - 12 |
| Comments: | Four small colonies are protected within municipal or regional parks, and one small colony is protected within a Wildlife Management Area. Private initiates are aimed at protecting the large colony on Salt Spring Island. Formerly Sidney Spit Provincial Park contained a large colony, but this has since been abandoned. (Butler in prep., Butler 1997). Blue Heron nest and nest trees are protected year-round by Section 34 of the Wildlife Act. |
| Population Size: | E = 2,500 - 10,000 individuals |
| Comments: | Precise numbers are not available, but the total population in British Columbia is estimated at 4000 - 5000 birds (Campbell et al. 1990a, Butler 1991). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Rank Factor not assessed |
| Comments: | Great Blue Herons are sensitive to exposure to environmental contaminants and pollutants which can lead to breeding failure (Elliot and Noble 1993). They also can be very sensitive to human disturbance at colonies. Loss of good nesting habitat near foraging areas may decrease reproductive output. These threats are particularly significant for A. h. fannini because its range overlaps that of a dense and rapidly growing human population in the Georgia Depression (Butler in prep.). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | G = Relatively Stable (<=10% change) |
| Comments: |
Periodically some colonies are deserted when the herons move to new breeding locations, often as a result of human disturbance or habitat loss, and possibly in response to Bald Eagle predation. Overall the provincial population is considered to be stable. ***46% decline over 3 generations (13.4 yr; 4.5% PA 1986-2006; Downes and Collins 2007)*** Short-term trend comments added ACT 2007-11-29 |
| Long-Term Trend: | Rank Factor not assessed |
| Other Factors | |
| Intrinsic Vulnerability: | Rank Factor not assessed |
| Environmental Specificity: | Rank Factor not assessed |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | Larger colonies should be monitored annually to detect trends in population and reproductive success. Other colonies and winter concentrations should be censused on a regular basis using standardized methods (Resource Inventory Committee 1997f #8) to monitor population trends and persistence of breeding colonies. |
| Stewardship | |
| Protection: | The species should be included in the species list of the proposed Identified Wildlife Management Strategy under the Forest Practices Code of British Columbia Act. Procedures for the establishment of Wildlife Habitat Areas on critical nesting habitats, and General Wildlife Measures to determine appropriate forest practices within established areas are required. |
| Management: | Human disturbance should be minimized at breeding colonies. Activities that negatively impact nesting Great Blue Herons should be avoided near breeding colonies during the six month period of March to August. Guidelines to reduce human disturbance near heron colonies (Summer 1996) should be implemented (Butler 1997b). Significant tidal flat and old-field foraging sites should be protected from development by acquisition or long-term stewardship agreements with nearby landowners. Eggshells should be collected regularly from selected colonies and assessed for toxic levels of environmental contaminants. Levels of pollutants should be monitored periodically in conjunction with data on reproductive success (Butler 1992). |
| Version | |
| Author: | S. Cannings and L. Ramsay |
| Date: | December 01, 1998 |
| References | |
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Butler, R.W. 1991. Habitat selection and time of breeding in the Great Blue Heron (Ardea herodias). PhD. Thesis, Univ. B.C., Vancouver. 99pp.
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Butler, R.W. 1992. Great Blue Heron (Ardea herodias). in A. Poole, P. Stettenheim, and F. Gill, eds. The Birds of North America, No. 25. Acad. Nat. Sci., Philadelphia, PA. and Am. Ornithol. Union, Washinton, DC. 20pp.
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Butler, R.W. 1997. Status report on the Great Blue Heron (Ardea herodias) in Canada. Comm. on the Status of Endangered Wildl. in Can. Available from Can. Nat. Fed. Ottawa, ON.
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Butler, R.W. 1997. The Great Blue Heron: a natural history and ecology of a seashore sentinel. UBC Press, Vancouver, BC. 167pp.
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Butler, R.W. 1999. Status of the subspecies of Great Blue Heron, Ardea herodias fannini, in Canada. DRAFT. Comm. on the Status of Endangered Wildl. in Can. Available from Can. Nat. Fed. Ottawa, ON.
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Campbell, R.W., N.K. Dawe, I.McT. Cowan, J.M. Cooper, G. Kaiser, and M.C.E. McNall. 1990. The Birds of British Columbia, Vol. 1. Nonpasserines: Introduction, Loons through Waterfowl. Royal B.C. Mus. in association with Environ. Can., Can. Wildl. Serv. 514pp.
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Cannings, R.J. 1998. The Birds of British Columbia - a taxonomic catalogue. B.C. Minist. Environ., Lands and Parks, Wildl. Branch, Victoria, Wildl. Bull. B-86. 266pp.
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Downes, C.M., and B.T. Collins. 2007. Canadian Bird Trends Web site Version 2.2. Canadian Wildlife Service, Environment Canada, Gatineau, Quebec, K1A 0H3.
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Elliot, J.E., and D.G. Noble. 1993. Chlorinated hydrocarbon contaminants in marine birds of the temperate North Pacific. Pages 241-253 in K. Vermeer, K. Briggs, K. Morgan, and D. Seigel-Causey, eds. The status, ecology and conservation of marine birds in the North Pacific. Can. Wildl. Serv. Spec. Publ., Ottawa, ON.
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Forbes, L.S., K. Simpson, J.P. Kelsall, and D.R. Flook. 1985. Great Blue Heron colonies in British Columbia. Unpubl. rep., Can. Wildl. Serv. Delta, BC. 78pp.
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Moul, I.E. 1998. The location and status of heron colonies around the Strait of Georgia: Region 2, Lower Fraser Valley, Sunshine Coast and the Powell River Area. Unpubl. contract rep. B.C. Minist. Environ., Lands and Parks, Nanaimo, BC. 146pp.
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Resource Inventory Committee. 1997d. Standardized Inventory Methodologies for Components of British Columbia's Biodiversity: Colonial Freshwater Nesters, version 1.1. Prepared for the Resour. Inventory Comm., B.C. Minist. Environ., Lands and Parks, Victoria, BC.
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Simpson, K., J.N.M. Smith, and J.P Kelsall. 1987. Correlates and consequences of coloniality in Great Blue Herons. Can. J. Zool. 65:572-577.
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Summers, K. 1996. Management Guidelines for Great Blue Heron Colonies in British Columbia. English 301 (Technical Report Writing) assignment. Univ. B.C., Vancouver, BC.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 1998. Conservation Status Report: Ardea herodias. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 8, 2026).