2.5 Great Blue Heron Ardea herodias

Biology

The Great Blue Heron is resident along much of the coast. Although widespread in British Columbia, the Great Blue Heron occurs as a nesting species primarily in the Southern Interior and Georgia Depression (Forbes et al. 1985; Breault 1988; Campbell et al. 1990). In winter, it is rare to uncommon except in the Georgia Depression where it is common.

Great Blue Herons are arboreal nesters and colonies are typically situated in mature forests that are relatively free from disturbance by human activities and near suitable foraging areas (Butler 1991, 1992). Nests are large stick platforms, mostly 15 to 30 m above ground. Clutch sizes range from 3-8 eggs. In successful nests, 2-3 young usually fledge (Campbell et al. 1990; Butler 1992).

Factors to consider for inventory of Great Blue Herons

• Colonies can be difficult to census as they are often high up in trees, dispersed in a few or many trees, and obscured by vegetation. To accurately count active nests, it may be necessary to climb trees; however this should only be done by a professional arborist.
• For surveys of intertidal foraging areas, tidal cycles need to be considered when choosing survey times, and analyzing data. Herons tend to use intertidal areas at low to medium tides and are rarely present on the foreshore at high tides.

Table 1. Location and maximum counts of nesting colonies

(data from Campbell et al. 1990)

Species	Locality	Maximum # pairs or nests
Red-necked Grebe	Stump Lake	64
	Charlie Lake	62
	Swan Lake (Vernon)	55
	Duck Lake (Creston)	55
Eared Grebe	Cecil Lake	1000
	Little White Lake	590
	Boundary Lake	500
	Westwick Lake	469
	McMurray Lake	440
	Elkhorn Lake	205
	Boudreau Lake	185
	Rock Lake (Riske Creek)	173
	Lake 6 (Williams Lake)	81
	Meadow Lake	79
	Lake 8432 N (Williams Lake)	72
	Stump Lake	61
	Sorensen Lake	50
	Dry Lake (Hanceville)	50
Western Grebe	Duck Lake (Creston)	90
	Okanagan Lake, north arm	83
	Shuswap Lake (Salmon Arm)	65
Great Blue Heron	University of British Columbia	183
	Port Coquitlam Indian Reserve	169
	Gabriola Island	138
	Salwein (Chilliwack)	130
	Duck Lake (Creston)	122
	Central Saanich	87
	Denman Island	70
	North Alouette River	65
	Parson	60
	Shoal Islands	60
	Edgewater Bar	59
	Prevost Island	59
	Stanley Park	44
	Brisco	40
	Beacon Hill Park	40
	Fairmont	35
	Sechelt	35
	Goat River (Creston)	33
	Otter Lake (Vernon)	25
	St. Mary's River	25
American White Pelican	Stum Lake	152