Monday, April 4, 2011

City herons

Vancouver's Stanley Park has the largest urban nesting population of Great Blue Herons in the world. At least that's what I overheard a lady birder saying when we were there last week. Stanley Park is immense and even wild in places, but 170 pairs (!) of herons choose to nest in 25 trees over-looking the busy tennis courts and parking lots.
It's a high-rise "herony" condo. They want a penthouse view to guard the nests from flying predators like eagles, hawks and crows. The park staff put metal collars on the tree trunks to keep cats, raccoons and other critters down. But other than a small wooden fence around the base of the trees, the nests are unprotected.

Herons are usually sensitive to noise and avoid humans, but this colony is acclimated to the city and has been nesting in Stanley Park for years. Herons repair and reuse their previous nests when they arrive back in February. The largest nests are the oldest and grabbed first-- herons arriving late have to build from scratch. The courtship rituals are dramatic and the female lays 3-4 eggs per clutch.

Once the eggs hatch, it takes only 60 days for a 4 inch bird to grow to 48 inches with a 6 foot wing span. Poor mom and dad. Their kids will eat until they are so stuffed their mouths hang open. (I didn't make that up.)

The first flight is a critical and often fatal crash course for the gawky little birds. They have only 2 weeks to learn to be self-sufficient before leaving for wintering grounds. Only about 15% survive their first birthday, but those that do have a good chance to live a long life.

And maybe have a Vancouver condo of their own someday.

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