Great blue heron (fannini subspecies) COSEWIC assessement and update status report: chapter 6
Distribution
Global range
The Great Blue Heron breeds from south coastal Alaska, coastal and southern British Columbia, northern Alberta, central Manitoba, southern Ontario and Quebec, New Brunswick, Prince Edward Island and Nova Scotia, south throughout the USA and coastal Mexico, and on the Galapagos Islands (Butler 1992). The winter distribution is south of the frozen regions in the north to as far south as Panama.
The distribution of the Pacific Great Blue Heron, which is the subject of this report, is confined to the coast from Prince William Sound, Alaska south to Puget Sound, Washington (Figure 1).
Figure 1. Global range of the Pacific Great Blue Heron, Ardea herodias fannini
B.C. Conservation Data Centre 2007).
Canadian range
In Canada, the Pacific Great Blue Heron resides year-round on the north and south coasts of British Columbia and associated islands (e.g., Vancouver Island and the Queen Charlotte Islands; Figure 2), including the Coastal Western Hemlock and Coastal Douglas Fir Biogeoclimatic Zones within 10 km of the coast or large river systems (see Habitat section for discussion). Most nesting colonies are located in the Strait of Georgia, the core of the subspecies’ range, and the only area where long-term data on nesting habitat are available (Figure 3). The area of occupancy is approximately 188 000 km2 and includes all terrestrial areas within the Coastal Douglas Fir and Coastal Western Hemlock biogeoclimatic zones that are less than 10 km from either the coastline or a major river system.The extent of occurrence is approximately 244 000 km2 and is based on a polygon with a minimum number of sides around the entire Canadian range. Approximately 59% of the global extent of occurrence occurs in Canada (approximately 128 000 km2 in Alaska and 43 000 km2 in Washington State).
Figure 2. Canadian range of the Pacific Great Blue Heron showing potential area of occupancy (shaded area).
Description of Figure 2
Potential area of occupancy is defined as terrestrial areas within the Coastal Douglas Fir and Coastal Western Hemlock biogeoclimatic zones that are less than 10 km from a potential foraging area. Potential foraging areas are defined as the entire coastline and major river systems (B.C. Conservation Data Centre 2007).
Figure 3. Documented nesting colony locations for the Pacific Great Blue Heron on the south coast and Vancouver Island of British Columbia from 1920 to 2005.
Description of Figure 3
Some nesting locations have been identified on other areas of the coast (e.g., Queen Charlotte Islands), but they are few and not based on significant inventory. The three primary regions of south-coastal British Columbia mentioned in the report (Vancouver Island, Sunshine Coast and lower Fraser Valley) are shown on this map (B.C. Conservation Data Centre 2007).
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