I have held a fascination of the ocean and the birds that live along its shores since I was a teenager. I was fortunate to know in high school exactly what I wanted in a career and what I wanted to study for a graduate degree. Researching birds along the shore became my career and eventually, it led to studying heron ecology for a doctoral degree. I have been interested in these birds ever since. Below is a summary of what we know about the herons in British Columbia where I reside.  

 A Brief History of Heron Research

In the 1970s, little was known about coastal herons in British Columbia. The pioneering studies of John Kelsall, Keith Simpson and Scott Forbes laid the groundwork for future behavioural and ecological work. They conducted censuses of colonies, banded herons at colonies and watched them at the breeding colonies and documented their foraging behaviour. A comprehensive census of nesting colonies in British Columbia was complied by Scott Forbes. At about the same time, concern about contamination of herons from industrial pollutants piqued the interest of Phil Whitehead and later John Elliot, Ross Norstrum, Kim Cheng, Ian Moul, Darin Bennett, and Leslie Hart. Their collective studies revealed much about the breeding, physiology, contamination and growth of young herons.  My studies began in the mid 1980s examining the ecology herons throughout the year. It was later augmented by research in the field by Ross Vennesland, Jamie Kenyon and Iain Jones.

My early research showed that herons nested near rich coastal foraging areas where they could catch enough small fish in coastal shallows to produce eggs and raise chicks.  Predatory eagles have since increased so that they are now an important consideration for where herons chose to nest. Overlying the changing predator landscape is the physical landscape we have built. Herons have had to cope with city life, land clearing, shooting, and pollution. They served as early warning systems for the build up of pernicious industrial contaminants. We have also come to realize that protecting the heron throughout its range would go a long way to preserving habitats of high conservation value for many species.   

The great blue heron and about 60 other species of herons belong to the genus Ardea. Its closest living relatives are the lovely black-capped and white-necked cocoi heron inhabiting the steamy tropical swamps of Amazonia and temperate wetlands of South America, and the similar looking grey heron of Europe and Asia. The triumvirate great blue, grey and cocoi are thought to be especially closely related and descended from a common ancestor that replace each other geographically. Taxonomists refer to them as a superspecies.      

The great blue heron is sufficiently different across its range that ornithologists have divided it into four (and sometimes more) subspecies. Its range is vast from the Pacific shores, across the mountains, prairies, northern hardwoods and Atlantic shores of Canada, south through the Atlantic seaboard and Florida Everglades west across the Midwestern river courses and Rocky Mountain marshes to the surf of California, the lagunas and mangroves of northern Mexico, and the remote shoreline of the Galapagos. In autumn it departs North American wetlands that become locked in winter ice and snow for open water some migrating as far as South America. It breeds from northern Mexico to southern Canada, and on the Galapagos. Herons do not migrate from the Pacific Northwest, southern USA, Mexico, and the Galapagos. Some herons in southern Canada and the northern USA remain all winter long where wetlands remain free from ice.

All of the four subspecies have the typical great blue heron shape - long legs, long necks and spear-like bills. The familiar adult great blue heron seen across most of North America has grey-blue plumage on the back, tail and wings, and neck, a whitish throat extending down the neck edged with dark vertical markings, white crown with black edges, and a yellowish bill. The scientific name is Ardea herodias herodias which means the heron heron heron.

The great white heron is given the unusual scientific name of Ardea herodias occidentalis or western heron heron. It is an odd name for a mostly white form of the familiar great blue that is confined to the Florida Keys and part of the Caribbean.  The Galapagos great blue heron is a resident subspecies confined to the archipelago belonging to Ecuador. It looks like a typical great heron except that the plumage on the neck is somewhat pale and its legs have a decided pinkish hue. Typical of herons, it wades in shallow water in search of hapless fish. Nests are built in shrubs and trees. It scientific name is Ardea herodias cognata or the heron’s heron relative.  The Pacific great blue heron resembles the typical heron form except that the plumage is darker especially on the neck, and the legs are shorter. Its scientific name is Ardea herodias fannini named in honour of John Fannin, former Director of the British Columbia Provincial Museum and well known 19^th century naturalist in Victoria.

The Pacific great blue heron nests from Washington to southern Alaska. In between, it resides on coastal islands and in fjords of southeast Alaska and British Columbia, and the coastal lowlands around Vancouver Island and Puget Sound. Most Pacific great blue herons forage along the seashore but a few also feed in freshwater marshes in the Fraser River and Puget Sound lowlands. Herons nesting along the Olympic Peninsula in Washington State are possibly Pacific great blues whereas the herons in Oregon are probably not but this distinction requires more investigation.  Many herons reside in urban areas of Vancouver, Victoria and Seattle and nest in large colonies in urban parks and suburban areas. Others nest in very remote locations away from all human activity including forests along the BC and Alaska coastline.   

Data from the recovery of bands attached to heron nestlings in the Strait of Georgia show that most do not leave the region. There are a few records of bands recovered in the interior of British Columbia and as far south as Oregon. Herons banded on the Sunshine Coast have been recovered on Vancouver Island. Band recovery data reflect the distribution of people as well as the movement of herons. It is not surprising that most bands have been recovered in the region but it is surprising that few have been found in the populated regions of neighbouring Puget Sound in Washington State. Adult herons have been seen flying across the Strait of Georgia between the Fraser River and the Gulf Islands.  These data suggest that the heron population has very little immigration and emigration.  The implication of this conclusion is that the effective population of herons might be quite small and vulnerable to local action.

How did this subspecies arise from pale-coloured herons that live to the east and south? We know that herons roam widely. Recoveries of our banded birds show that some herons travel great distances. Herons have reached the Galapagos Islands and there are records for they Yukon and Hawaii.

The coastal subspecies A. h. fannini  designation is based on phenotypic difference from other great blue herons, most notably the darker colour and shorter legs of the former. Robert Dickerman’s review of heron plumage and measurements concluded that A. h. fannini should be confined to the herons on Haida Gwaii and adjacent mainland coast and southeast Alaska. His conclusion has not yet been officially adopted and some genetic research could shed some light on this issue.

There are several subspecies of birds on Haida Gwaii that likely arose during a period of an ice-free refugium during the late Wisconsin glaciation. An ice-free plain connected the BC mainland to Haida Gwaii that today is underwater. Pollen evidence from cores bored into the submerged plain tells of an ancient land of freshwater lakes and marshes similar to where herons live today. Mitochondrial DNA evidence from a suite of other species from mosses to bears points to this submerged land as the Eden for many coastal subspecies now living on higher ground among the islands along the BC coast. In the isolation of the ice-free refugia, a small population of herons could have begun to adapt to a wet coastal environment. As the ice melted further, the heron extended its range along the coast into present day Alaska and toward Vancouver.   

If the southern border of A. h. fannini is the central coast of BC, then what designation should be applied to the great blue heron near where I live on the south coast of BC? Herons on the south coast are larger than their northern relatives and smaller than California specimens.

Scientific name: Ardea herodias fannini

Distribution: Eastern Pacific shoreline and all fjords and large islands between Puget Sound, Washington (Olympia) and southern Alaska (Kodiak)

Non-migratory. Disperses to foraging habitats along seashore mostly near nesting areas but some young herons have traveled hundreds of kilometers

Food: Mostly small fish but also crabs, small mammals, snakes and birds. Most foraging is within a few kilometers of the nesting colony. Maximum distance is about 10 kilometers. Prey items are killed and swallowed whole. Food is carried to the nest in the throat and regurgitated into the nest.

Mating Strategy: Mostly monogamous pairs during nesting season. Probably choose new mates in subsequent years.

Eggs Stage: 3-5 pale blue eggs are laid in April and May. Second nesting attempts are made until June. Incubation is about 27 days. Eggs hatch asynchronously. 

Chick Stage: Chicks are brooded by both parents nearly continually for about 3 weeks post hatching. Female parents forage mostly during the day and incubate and brood at night. Males do the opposite. After about three weeks, both parents forage during the day. Chicks perch in branches of trees and depart the nest after about 55 days of age.

Life Span: Uncertain but based on survival of marked herons, most adults probably live about 10 years and some probably live to be about 20 years.

Conservation Status: Schedule 3 in Canada’s Species at Risk Act (March 2010). When a species is added to Schedule 1 as a species of special concern, SARA requires the preparation of a management plan to prevent them from becoming endangered or threatened.

Population Size: About 10,000 herons across the range. About 1000 to 1500 nesting pairs around the Strait of Georgia, 2000 pairs around Puget Sound. Scattered along the coast north to southern Alaska. The population on Haida Gwaii (the site of the fannini type specimen) is probably no more than 100 pairs.

Age of maturity: Most at two years although some yearlings attempt to breed.

Birth Rate: About 2 young per successful nesting attempt. Nesting success is highly variable with abandonment being a major factor. 

Eggs

Great blue herons lay pale blue eggs measuring about 6 cm long and 4 cm in diameter. Freshly laid eggs weigh about 70 grams. Adult herons have brightly coloured bills and feather plumes on their breasts a few weeks before and during egg laying. The colours fade and the plumes are shed soon after eggs are laid.

Nestlings

Chicks at hatching have sparse grey down on the body and wings, a tuft of whitish feathers on the crown and stout wing and pinkish grey legs. They will sport these white tufts until soon after they leave the nest. Newly hatched chicks utter a faint tik-tik-tik sound within minutes of hatching. They grow quickly first to a crouching position and then to a standing position. The calls get louder and more raucous that is unending day and night. The young herons perch on the nest before moving into branches in the nest tree to practice flapping their wings. One or two nestlings are often killed, starved or fall to their deaths. Parents that succeed, can expect to raise an average of slightly more than two chicks.

Juveniles

A heron is a juvenile from when it leaves the nest until the start of the following breeding season. Juveniles lack the body plumes, white crown feathers, black occipital (eye) plume of the breeding adult. Their crown feathers are slate gray. Their wing coverts are edged with cinnamon brown tips, and the feathers on the neck are generally streaked brown.

Yearlings

A juvenile becomes a yearling when it is 12 months old. Yearlings resemble adults except that they have a small amount of white on the crown. The edge of some wing coverts are tipped with brown. They have short or no plumes.

Adults

A heron becomes an adult when it is two years old. They are generally a slate grey on the back and hind neck. The crown is white and the forehead varies from white to grey. This feature might be age-related. A black plume emerges from the posterior end of a black line above the eye. The eye is yellow rimmed with black. The bill is greenish grey on the upper mandible and yellowish on the lower mandible during the non-breeding season. The bill turns yellowish-orange during courtship and egg laying. The side of the neck is buffy brown, especially in the coastal subspecies. The foreneck is white with cinnamon and chocolate brown streaks. Plumes on the breeding adult spill from the back over the folded wing and sprout from the chest. Some of these feathers are dropped soon after the eggs are laid. The primary flight feathers and the flanks are black. The bend of the wing and the upper legs are cinnamon brown. The legs are greenish grey with yellow-green soles. Sexes are similar although females are generally slightly smaller than males. This difference is most pronounced in bill length.

Best Places to See Herons

A large nesting colony of 300-400 pairs gathers between March and July at the foot of the BC Ferry terminal at Tsawwassen south of Vancouver each year. You can park alongside the terminal road at a pull out on the east side where there are superb views of herons on nests and flying to the tidal flats to catch fish. With binoculars, you can see up to 800 herons foraging on the nearby beach. Over 100 pairs nests in trees each spring near the headquarters of Stanley Park in downtown Vancouver. Enter the park from Beach Avenue. 

Further Reading

Butler, RW. 1997. The great blue heron. University of British Columbia Press, Vancouver. This book summarizes much of what I have learned about herons and my experiences following them around the year.

Butler, RW. 1992. Great Blue Heron (Ardea herodias). The Birds of North America (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology.