A breeding colony of blue herons in Vancouver’s Stanley Park is anything but normal; it’s a noisy, busy place with many human activities, yet experts say the birds somehow thrive.
It’s this time of the year when the Pacific great blue herons are seen high up in the treetops at Stanley Park, screeching, flapping their broad wings and bringing sticks to impress potential mates.
The herons, which were first documented in Stanley Park in 1921, are returning to the park’s rookery high above the tennis courts where they’ll court, build nests, lay eggs and parent their chicks.
Nadia Xenakis, an Urban Wildlife Programs coordinator at the Stanley Park Ecology Society, said it's mating season and the public gets a front−row seat to the ritual of male herons carrying sticks to the nest of a possible mate.
If she weaves the stick into the nest, she’s attracted; if she drops the stick to the ground, he’s out, Xenakis explained.
Stanley Park’s colony is “incredibly abnormal,” said Xenakis.
It’s way too loud and there’s too much human activity, she said.
“People play tennis all day, you have cars driving through all day, and you have dogs walking by all day,” said Xenakis.
Yet the herons thrive each year.
About 90 chicks were born last year, even as the colony overcame persistent eagle raids and a nesting season delayed by winter weather, the Vancouver park board said in a news release.
Ross Vennesland, an Environment and Climate Change Canada researcher, said it’s a “little bit of a mystery” to see the herons in Stanley Park, because they usually prefer to nest in quiet places.
This spot, however, also has some benefits, said Vennesland, who has been studying herons since the ’90s.
“They might see it as having fewer predators, perhaps lots of people, but the people don’t really bother them very much. So, you know, herons do adapt to people fairly well in some circumstances and Stanley Park is definitely one of those," he said.
“And it doesn’t have any eagle nests, so, it definitely is a good spot for them. And that probably explains why they’ve been there now for so long."
Maria Morlin,a biology instructor at Vancouver Community College who has been watching herons for 20 years from her nearby apartment, said there are a lot of theories about the park’s heron colony, including that the location grants them easy access to food.
"Herons don’t like to fly more than about 10 kilometres from where they breed because otherwise it takes up too much energy," said Morlin, who likened the large birds to "flying dinosaurs."
The peninsula of Stanley Park is surrounded by the waters of English Bay and Burrard Inlet, giving the colony’s members plenty of shoreline from which to feed.
Blue herons usually lay from two to five light blue eggs between February and April that hatch in about 30 days.
Xenakis said there has been a decline overall in fledglings since 2001, when there was a high point of about 254. Now they are seeing about 90 every year.
The downturn in the population has been linked to the decline in habitat quality, increasing urban expansion, and attacks from eagles that go after the eggs.
Vennesland has seen eagle attacks and said it’s a dramatic scene when the eagles arrive at the colony, the herons begin to scream and fly in circles.
"Some may defend their nests, but a lot of them just flee. It’s a quite unnerving sight for sure," said Vennesland.
From the evolutionary perspective, Vennesland said many of the birds live a fairly long life will give up their nest of eggs to save themselves.
However, adult herons will defend chicks when they are older, added Vennesland.
There are around 4,000 to 5,000 blue herons in Canada, with one−third of them living around the Salish Sea off B.C.’s coast.
Xenakis said it’s sometimes easy to take the blue herons for granted because they’re all around the Lower Mainland.
People need to be aware they’re sharing the area with these beautiful birds, she said.
“If we are kind of destroying habitat, feeding wildlife, things like that can be really disruptive for local wildlife.
"So, just make sure we are being like good citizens of the forest and not leaving a trace behind and causing harm to the animals that are there,” said Xenakis.
People passing by the heron colony area between mid−March to mid−July are encouraged to keep pets on a leash and refrain from flying drones around nesting birds.
Bird lovers can also watch the herons live from Stanley Park via the Heron Cam on the City of Vancouver’s website.