With a little sunshine and warming weather, spring certainly seems to be in the air. At least, that's what the birds seem to think.
The large winter feeding flocks of small songbirds have long dispersed and most of our resident birds are now paired up with a mate for the coming season. Even though the nesting season is not yet quite here, the hunt is on for suitable nesting sites.
Last week along Noons Creek, I watched, entranced, as a Bewick's wren thoroughly investigated every nook and cranny in search of the best possible nesting cavity.
Early spring is a wonderful time to enjoy the birds at Colony Farm Regional Park in Coquitlam. Two upcoming guided nature walks, with a focus on great blue herons, will be offered on Saturday, March 19 and Sunday, March 27. The walks will start at 9:30 a.m. and last approximately two hours. Led by volunteers from the Burke Mountain Naturalists and Colony Farm Park Association, the walks will also provide an opportunity to learn more about the habitat at Colony Farm and why so many species of birds are found there. The walks will start from the parking lot at the far end of Colony Farm Road, which intersects at a traffic light with Lougheed Highway.
Great blue herons are one of several species at-risk that rely on habitat at Colony Farm. During spring and summer, herons catch mostly fish or frogs for food. They can often been seen along local creeks and shorelines or, sometimes, in the ditches at Colony Farm.
Herons are solitary hunters that patiently wait in shallow water until a small fish swims within the reach of its long neck. During the fall and winter, when fish are less abundant and water is sometimes frozen, herons turn to the open fields at Colony Farm, where they catch meadow mice and small voles. These voles are an important prey item at Colony Farm for several species of raptors as well as great blue herons.
Because these herons are relatively common locally, many people are surprised to learn they are a species at-risk. Unlike the great blue herons found across most of Canada, the herons along this portion of the west coast do not migrate south in the fall. Thus, they form a unique non-migratory subspecies of herons and it is this subspecies that is at-risk.
These herons typically nest in a colony in groves of large trees within a few kilometres of their feeding sites. Along the coasts of southwest mainland B.C. and Vancouver Island, many trees have been removed to make way for houses and highrise towers. Thus, herons have lost much of their essential habitat in the last century.
One of the largest heron nesting colonies in the Lower Mainland is found at the mouth of the Coquitlam River in a provincially-protected Wildlife Management Area. The herons found at Colony Farm come from this nearby colony.
It is the excellent and reliable winter feeding opportunities in the fields at Colony Farm that are thought to account, in large part, for the success of this growing colony. While herons do not appear to form pair bonds until they move to the nesting colony in late March, they start to congregate in large groups in February. By late March, Colony Farm provides the unusual sight of as many as 50 herons in one large group.
Because stands of tall trees are now in short supply throughout the Lower Mainland, herons must often share their space with nesting bald eagles. This has become more frequent in recent years as eagle populations have rebounded following the prohibition of harmful pesticides, particularly DDT.
Because eagles are known to predate upon heron chicks, it seems surprising these two species would share their territory. But biologists believe that having one eagle nest nearby actually helps to protect a heronry from predation by other eagles. Losing an occasional chick to a single pair of eagles appears to be the price paid for security from a larger number of other hungry eagles.
The great blue heron walks at Colony Farm are offered free of charge and no registration is required. Families with young children are most welcome. The walks will be on level ground that can be rough in places so people are encouraged to wear sturdy shoes and bring binoculars, if possible.
For more information, visit www.bmn.bc.ca.
Elaine Golds is a Port Moody environmentalist who is vice-president of Burke Mountain Naturalists, chair of the Colony Farm Park Association and past president of the PoMo Ecological Society.
