Pilgrim at Taddle Creek

Virtually every day for twenty years, I have walked my dog (more accurately, one of two successive dogs) around Wychwood Park in Toronto. This green oasis sits on the former shore of the prehistoric Lake Iroquois. Under a canopy of 300-year-old oaks, the air is fresher and cooler in summer, the wind less biting in winter. Birdsong provides a constant symphony, and before the trees are fully leafed in, you can see migrant warblers as well as the resident red-tailed hawks tending their eyases on the west side of the pond.

Since the hawks built their lofty residence a few years ago, mallards no longer brood nearby as they once did — their fluffy little offspring being tempting snacks — but they often visit in late summer or fall when the ducklings have reached the size of their parents. There used to be plenty of fish breaking the water to catch insects, but one sad summer a voracious cormorant ate most of them; the painted turtles mysteriously disappeared about the...