6/08/2011

Forest Creatures: Great Blue Herons

Endangered Great blue herons live in the coastal forest

It was on one of my hikes of Vancouver Island's West Coast Trail that I learned of an endangered species living in the coastal forest. Great Blue Herons, the largest North American herons, are year round residents. And they build their nests in trees.

We were hiking toward Nitinat Narrows when we first heard the primeval squawk of Great blue herons. As we approached, the noise was a discordant symphony of primitive vocalizations - it was the first heronry I had ever seen, or heard, and it was both chaotic and beautiful.

Heron chicks on the nest
It seems weird for these long-legged, large birds to be hanging out in the tops of tall trees. They seem more comfortable stalking prey in shallow water.

But for the part of the year when they are nesting, they make their large homes built of sticks at the tops of huge coastal trees.

Although herons are on the endangered species list, it would be hard to tell during a visit to the south island area. There are many herons around, including in my own neighbourhood. It is not uncommon to see up to 10 herons tolerating each other in rich, low tide seaweed beds of the Sooke River estuary. One can also find heron nesting sites in several locations, including one urban heronry in Beacon Hill Park in Victoria.

While herons are not social for most of the year, when it comes to breeding time, around March, these solitary birds come together in large groups. The Beacon Hill Park herons had established a large heronry in the 1980s, numbering up to 100 nests at its largest. It was a rare urban wildlife experience. Until 2007, when a resident bald eagle started to prey on the heron's nests.

Heron parents defending their nest from another Birdzilla attack in 2007, Beacon Hill Park

The eagle, nicknamed 'Birdzilla', quickly tore through the heronry, and within the course of a weekend had gone through 71 nests and consumed 39 chicks and 187 eggs. The herons, as herons will do when harassed by predators, bailed as a group, and abandoned their long-time nesting site. Some herons returned to the park in 2010 to establish new nests. Herons have been seen taking sticks from the old nests to build new ones.

Herons swallow food whole - some have been known to die in the attempt

Herons can be found in a range of habitats such as fresh and saltwater marshes, mangrove swamps, flooded meadows, lake edges, or shorelines, but are always found close to bodies of water. Their tree top nesting sites are usually always no more than a few kilometers from aquatic feeding grounds.

The primary food for Great blue herons is small fish, though it is also known to feed on a wide range of shrimp, crabs, aquatic insects, rodents and other small mammals, amphibians, reptiles, and small birds.

Photo credit: all photos (except Beacon Hill eagle attack) from Wikipedia
Beacon Hill photo: Rhiannon Hamdi

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