Nothing invokes primeval times like the call of a great blue heron. The giant bird’s cry—a rasping, croaky wonk—is a haunting echo from an age when its dinosaur ancestors ruled the skies. “You’ll definitely hear them before you see them,” Dylan Schroeder, a seasonal guide at Chilliwack’s Great Blue Heron Nature Reserve, advised the Georgia Straight during a visit. “Herons emit a prehistoric sound, clucking and squealing like a stuck pig.”
Schroeder handed out binoculars to eager visitors while directing others to a viewing scope mounted on the outside deck of the interpretive centre, beyond which a network of spongy forest trails and hard-packed, bike- and stroller-friendly dike routes led off into the Fraser Valley countryside near the Vedder River.
With outstretched wings lazily beating, scores of great blue herons circled gracefully above a nearby black cottonwood forest before gliding onto some of the 168 active nests buried deep inside the foliage, where there was just enough room for the gangly parents to alight. With wings folded, their profiles became as spindly as the fence posts in the surrounding farm fields of Chilliwack’s Greendale neighbourhood. The objects of their attention were hatchlings whose hungry racket rivalled a barnyard full of clucking chickens.
A bald eagle circled high above the rookery in search of an opportune opening in the leafy canopy to raid a nest. As Birds Studies Canada scientist Rob Butler explained to the Straight by phone, eagles are now the herons’ greatest threat. “Many heron colonies around the Lower Mainland were disturbed by the rebound in eagle populations in the 1990s after bald eagles had all but disappeared in the 1960s.”
In the same breath, Butler pointed in admiration to the adaptive behavior exhibited by great blue herons. “There’s a symbiotic relationship we’ve observed in places such as beside the B.C. Ferries jetty in Tsawwassen—site of some 300 nests—where herons have learned to align themselves with a single pair of nesting eagles whose territorial imperative is to keep other would-be predatory eagles away. The adaptive behavior we’ve observed among herons is that they’ve learned to move in tandem with nesting eagles for self-protection. It’s the choreography of nature, the dance between species that, in the case of herons, has been going on for about 14 million years.”
Spring days in April and early May, before trees fully leaf out, are the best times to witness heron-courtship rituals on dramatic display. One of the easiest places to observe such elegant behaviour is the rookery in the southeast corner of Stanley Park, beside the tennis courts, home to 117 nests.
Robyn Worcester, Stanley Park Ecology Society conservation-programs manager, told the Straight by phone that the big-leaf maples, oaks, and London plane trees there are the current home of a local colony that has inhabited the park since at least the 1920s. “Great blue herons have a long history in Stanley Park, way longer than me,” the 34-year-old registered professional biologist—whose parents brought her to the park on the day she was born—laughingly explained. “The colony has been in their current location since 2001, when they moved over from around the aquarium.”
What prompted the shift? “Where they nest gets covered in guano, which kills the trees and forces flocks to find new homes. Every year we hold our breath to see if they come back from their winter habitat on local foreshores where they stalk fish and hunt for easier prey, such as voles that number in the millions.”
Unlike migratory great blue herons in other parts of North America, local coastal species spread between Puget Sound and Alaska stay close to their nesting colonies all year. “The largest concentration of great blue herons is in the Georgia Strait basin,” Worcester pointed out. “Because of this, people see them all the time.”
In actual fact, studies by SPES and related agencies have shown heron population numbers are in decline and the species will probably need to be upgraded from the current B.C. “blue list” vulnerable designation. “When people in the city complain about the noise and smell, I tell them herons are not to be taken for granted,” Worcester said.
As a founding member of the Heron Working Group, Butler shared Worcester’s concern. “Our group formed in the 1990s when I was working with the Canadian Wildlife Service,” said the retired SFU professor whose résumé lists being the founder of the Young Naturalist Club and past president of the Pacific Wildlife Foundation as among his many accomplishments. “We tracked elevated levels of contaminants such as dioxin in heron eggs. I’m happy to report there’s been a complete turnaround. That’s the good news.”
In general terms, Butler, who will lead guided walks in Stanley Park as part of joint SPES- and City of Vancouver–sponsored activities during the third annual bird week (May 4 to 11), classified the local natural environment as “the most favourable spot for birds on the Pacific flyway. I often hear people say on my tours, ‘I never knew they were there.’ Once people see birds, they become more aware of our natural surroundings. We know green spaces mean healthier lives. If there are lots of birds around, that means it’s probably good for us too.”