Great Blue Heron

Of the five subspecies of Great Blue Heron two live in Canada; the Great Blue Heron (Herodias) and the Pacific Great Blue Heron (fannini). The Pacific Great Blue Heron, as its name implies, is found along the Northwest Pacific coastline from Alaska to Washington and is unique because they stay year round, whereas other subspecies migrate seasonally.

Great Blue Herons are the largest wading birds in North America standing nearly 1.5 meters tall with their necks extended, and can have a wingspan of 2 meters! Despite their large size they only weigh an average of 2.5 kg! Compared to other waterfowl, a Canadian goose may stand approximately 1 metre tall with its neck stretched out with a wingspan of about 1.5 meters and they weigh on average 6 kg. If you think about it in human terms, herons are as tall as an average 8-year-old child but only weigh as much as a newborn baby.

Adult herons are blue-grey and typically have shoulder patches of black and brown, a black stripe over their eyes, and shaggy plumes on their head, chest and wings. They have a long pointy bill, tall stilt-like legs, and lengthy toes that are used to curl around perches. In preparation for the mating season, their colours become brighter, and their plumes grow longer. In summer they will moult some of their plumes and become a duller colour over winter. The Pacific Great Blue Heron is slightly darker in colour and smaller in size compared to the Great Blue Heron. Herons live on average about 15 years, however, the oldest one recorded was 25 years old.

The Great Gathering.

The majority of the remaining adult herons in Canada nest and breed near the Straight of Georgia, typically in woodlands near the water, however, may be found nesting on the ground as well. Although a heron couple may nest alone, they prefer to nest in large colonies isolated high up in trees, as they are easily disturbed. These colonies aid in protecting the young from predators as well. Nesting colonies may be reused for many years however smaller colonies consisting of less than 25 nests may be relocated more frequently. There can be hundreds of nests in a single colony!

Annually, herons build or repair sturdy platform-like nests out of large sticks, lined with a variety of materials such as moss, pine needles, and dry grass. This can take them just a few days or a couple of weeks to complete. Nest size can vary greatly depending if it’s a new nest or one that has been used for many years. Older nests tend to be much larger and can be more than a meter across and thick. Great Blue Herons are not the tidiest of birds and often their nests are full of droppings, leftover food and even chicks that didn’t survive. Herons are not social birds but they gather in the spring to mate; Pacific Great Blue Herons begin slightly earlier than other subspecies, between February – April. Males begin courtship by choosing and defending a nest or nesting tree and gather sticks which they present to the female who will weave them into the nest. With bright colours and long plumes, males put on a display for approaching females by making a lot of noise, loud bill snapping, twig shaking, circular flights, and preening. Herons will find a new mate each year, however, are monogamous during mating season.

On average herons lay approximately 3-5 eggs, although Pacific Great Blue Herons typically have smaller clutch sizes. Eggs hatch in approximately 1 month, and within 2 months after hatching the juveniles will be able to fly. Both parents will help to incubate the eggs and care for the chicks. It has been observed that males take the day shift and females take the night.

Unfortunately less than half of the eggs will make it to fledging, and those that do have less than a 25% chance of making it through their first winter. Often chicks will die because of sibling rivalry, sometimes from starvation because the more dominant the clutch is fed more often. More aggressive chicks may even push others out of the nest. The survivors will leave the nest around 8 weeks old and will follow their parents to the feeding grounds. Those that survive their first winter have increased survival rates of about 75%.

Great Big Appetite!

Herons are carnivores and eat a wide variety of things from fish, frogs, small mammals, and even other birds, and are fantastic hunters day and night thanks to having excellent night vision. They spend nearly 90% of their time awake in search of food, and because they require a lot of food herons protect their feeding ground more intensely than they defend their nests. Herons love to eat so much that they’ve been known to overestimate how much they can handle and end up choking to death on large fish.

They can be found along the seacoast as well as freshwater marshes, rivers, and even the grasslands. When hunting in the grasslands herons will catch voles and mice and swallow them whole! Everything but the fur can be digested, and similar to an owl, they cough up fur pellets to expel the undigested bits.

Herons are equipped with a blade-like bill to skewer fish with and have a lightning-fast strike due to specially shaped vertebrae in their necks. They position themselves with their necks stretched out and patiently wait motionless for a meal to pass by below them before making a deadly strike.

Herons’ bodies are equipped with a built-in cleaning mechanism, so luckily they don’t get as messy as their nests from all the slimy fish. On their chests, they have specialized feathers that continuously grow and will eventually fray into a powder which they use to clean off any slime from their most recent meal.

A vulnerable species; greatly threatened.

Great Blue Herons are considered vulnerable and are protected and designated as a special concern. This means they are not on the endangered list however are highly sensitive and may end up there if precautions are not taken. Canadian populations of Pacific Great Blue Herons are estimated to be as low as 4,000 – 5,000 nesting adults, approximately 3,300 of which live near the Salish Sea. Globally there are less than 11,000 nesting Pacific Great Blue Herons remaining. Great Blue Herons have seen a significant decline in the rate of reproduction since the 1970s as a result of habitat destruction from urban growth and logging, and increase in bald eagle populations.

Heron population size is directly correlated with the habitat. Where there is more foraging available there are larger populations of herons, such as extensive mudflats, or eelgrass beds. Prime coastal areas in Southern British Columbia have seen a decline in nesting herons because of the growing human population impacting the quality and availability of foraging and nesting habitats. Quiet areas with big enough trees to nest in are becoming rare. Herons can tolerate some human presence however they are sensitive to human activities and easily disturbed. As far as 200 meters away, human presence can cause a heron to abandon a nest. Studies have shown that herons nesting near populated areas have a much lower rate of fledgling survival compared to those in isolated areas.

When herons are disturbed they leave the nest which results in the young being left defenceless to predators. The Bald Eagle is the primary predator of the Pacific Great Blue Heron, and with eagle numbers on the rise since the 1980’s, attacks on heron nests has increased substantially. Raccoons also pose a threat as they’ve been known to climb into nests and attack the chicks. In 2009, 44 nests were raided primarily by raccoons in Stanley Park. Increased numbers of predators can cause colony abandonment, and forces herons to nest in lower quality sites.

Human impact in the form of chemical pollutants may also be impacting heron populations, with tissue samples presenting higher toxicity levels than in the past. There has not yet been enough research to fully understand the impact however if waters are full of contaminants, species living in the waters will also be contaminated, which the birds then consume.

How Can We Help

Great Blue Herons are protected by government policies, which is a start, but they can use as much help as they can get. Herons require large trees and adequate feeding grounds; so by protecting large trees near shorelines, giving them space to nest and feed, and reducing disturbances, it’s a great help. Efforts are being taken to protect nesting herons in PKOLS – Mount Douglas, among others. Fences have been built to restore the habitat, and the area will be blocked off to human traffic when nesting begins. This is to reduce disturbance from human activity, but also protects humans from falling sticks, and being the victim of guano splatter.