Great blue heron (fannini subspecies) COSEWIC assessement and update status report: chapter 5
Species information
Update
COSEWIC Status Report
on the
Great Blue Heron
Ardea herodias fannini
fannini subspecies
in Canada
2008
Name and classification
The Great Blue Heron, Ardea herodias, belongs to the Class Aves, Order Ciconiiformes and Family Ardeidae. It is a distinctive heron species found in wetlands across southern Canada and is the largest wading bird in North America (standing over 1 m in height).
Five subspecies currently are recognized (Payne 1979; Butler 1992), two of which occur in British Columbia. The subspecies Ardea herodias herodias occupies all of southern Canada east of the coastal mountain ranges of British Columbia, while the subspecies Ardea herodias fannini occupies the whole British Columbia coast west of the mountain ranges (Figure 1).
Morphological description
The Great Blue Heron measures about 60 cm in height (with neck relaxed), 97 to 137 cm in length, and 2.1 to 2.5 kg in mass (Butler 1992; 1997). The wings are long and rounded, the bill is long, and the tail is short (Butler 1992; 1997). Great Blue Herons fly with deep, slow wing beats and with their necks folded in an S-shape. Plumage is mostly a blue-grey colour and adults have a white crown (Butler 1992; 1997).
The Pacific Great Blue Heron differs from the continental form (A. h. herodias) in morphology and breeding behaviour/physiology (Butler 1997). In terms of morphology, the Pacific Great Blue Heron is smaller in size and darker in plumage than A. h. herodias.
Genetic description
Genetic characterization of Great Blue Herons in North America has not been conducted.
Designatable units
The American Ornithologists’ Union (A.O.U.) recognizes one coastal subspecies of Great Blue Heron in British Columbia referred to in this report as the Pacific Great Blue Heron (A. h. fannini).
A recent comparison of heron taxonomy showed that specimens on the Queen Charlotte Islands, the north coast and southeast Alaska had shorter tarsii and darker plumage than specimens on the south coast (Dickerman 2004). South coast herons were intermediate in size between the north coast and specimens from California (Dickerman 2004). From these data, Dickerman (2004) recommended that the fannini subspecies designation be restricted to the Queen Charlotte Islands and adjacent north coast of British Columbia in Canada and Alaska, and that south coast herons be considered an intermediate form with California herons. This recommendation has not been considered by the A.O.U. and stands in contrast to the currently accepted designations based on work by Payne (1979), which also was based solely on morphology. Genetic evidence would assist in clarifying the degree of separation of subspecies and geographical boundaries.
This report considers one designatable unit, which is the single coastal subspecies of Great Blue Heron, as per currently accepted A.O.U. taxonomy.
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