By LAURA MATTHIAS

Special to the Driftwood

Standing over one metre tall, the great blue heron (Ardea herodias) is the largest heron on North America.

The non-migratory, coastal subspecies (Ardea herodias fannini) is federally listed by the Committee on the Status of Endangered Wildlife in Canada as “special concern” (defined as a wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats).

This stately bird nests in colonies, called heronries, sometimes with several hundred nests in one heronry. Herons prefer quiet forested locations within a few kilometres of their feeding grounds for nesting sites. They often feed on fish and amphibians in eelgrass beds, grasslands, beaches, and estuaries.

Quiet, undisturbed forested areas near waterfront foraging habitat are becoming harder to find in the populated southwestern B.C. coast. Herons have also been in decline due to habitat loss and other factors, such as a rise in bald eagle populations. Heron chicks often fall prey to these predators.

The predation is compounded when herons are disturbed during the nesting season, often by human activities. This causes the adults to fly off the nests, leaving the helpless chicks exposed to predation.

Nesting in colonies may be one mechanism for ensuring that the predation is dispersed over several nests. But it can also provide a smorgasbord of food for predators once familiar with a colony location.

Productivity of coastal herons has been documented to have been in decline for a number of years.

Many large, historic colonies on the coast, including Salt Spring’s own McFadden Creek heronry and the neighbouring Crofton heronry, have abandoned their traditional nesting sites and dispersed.

Trudy Chatwin, rare and endangered species biologist with the Ministry of Environment, has been studying and documenting heron colonies with others for many years on B.C.’s coast. She has observed that the herons seem to be dispersing into smaller colonies, possibly as a means of trying to stay under the radar of bald eagles and other predators for as long as possible during the breeding season.

However, smaller colony sizes may also reflect that there are fewer herons out there. Chatwin notes that the smaller colonies do tend to fail over the long term.

As part of the Salt Spring Island Conservancy Stewardship Project, the conservancy is interested in hearing from you if you have seen groups of herons nesting in trees. Call us at conservancy at info@saltspringconservancy.ca or 250-538-0318.

If you live near a heron colony, take care to avoid disturbing them, especially during the remainder of their nesting season for the next couple of months.