The largest Canadian Heron (total length 108 -132 cm). Head white with broad black stripe on either side. Upper parts mainly greyish-blue. Underside variously streaked and marked with black and white. Bill yellowish, broad at the baser, tapering to a sharp point. (Godfrey, 1986).

Columbia Basin: locally distributed throughout the Columbia Basin north to about Golden and Revelstoke.

British Columbia: 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 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 (Cannings et al. In prep.).

Global: A. h. herodias breeds from southeast British Columbia, northeast Washington, northern Alberta, central Saskatchewan, southern Manitoba, central Ontario, southern Quebec and the Maritime provinces south to Montana, Nebraska, Missouri, Illinois, West Virginia, South Carolina and Bermuda. Winters throughout the breeding range (except on the Canadian prairies) and south to northern South America (Cannings et al. In prep.).

(Cannings et al. In prep.).

The total population in British Columbia is estimated at 4000 - 5000 birds. 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. Great Blue Herons are sensitive to exposure to environmental contaminants and pollutants that can lead to breeding failure. They also can be very sensitive to human disturbance at colonies. Loss of good nesting habitat near foraging areas may decrease reproductive output. (Cannings et al. In prep.).

In coastal British Columbia, nesting colonies are all within 8 km of suitable foraging areas, and most are within 3 km. Most colony sites, left undisturbed, are used year after year. Other colony sites are ephemeral, and once abandoned birds may or may not return to the same site in later years. Colony size varies from 1 to 169 nests, with most (46%) colonies consisting of 1 - 10 nests (Cannings et al. In prep.).

Great Blue Heron nests in British Columbia are typically a large stick platform, up to 1 m in diameter, with a nest cup lined with small twigs, bark strips, evergreen boughs, or rushes. Nest trees are usually deciduous, although a wide variety of tree species (at least 15) are used. Great Blue Herons feed primarily on fish, but also on a variety of amphibians, invertebrates, reptiles, small mammals and birds. Roost sites include jetties, log booms, and coniferous trees. Migrant Great Blue Herons arrive at colonies in March and April. Although clutches have been observed from early April to early July, most nesting occurs between mid-April and early June. Clutch size ranges from 1 to 8, with 3 - 5 eggs being most common. The incubation period is 25 - 29 days and brood size ranges from 1 to 8 young (2 or 3 being most common). The fledgling period is approximately 60 days. Non-breeding birds may disperse northwards in May and June, followed by young from southern breeding colonies in July and August. Those that migrate south in the fall do so in September and October. (Cannings et al. In prep.).