Leslie Scrivener Staff Reporter Dark and swift, flocks of cormorants soar above Lake Ontario before hundreds of them finally dip down to the diamond-flecked water. It's a stirring sight on a bright spring day.

But cormorants are less beautiful on land.

One arm of the Leslie Street Spit, home to Tommy Thompson Park and the Great Lakes' largest colony of cormorants, looks like a wintry apocalypse. There are no trees now, just a few guano-spattered snags. This is where cormorants first settled in the park in 1990. They now number about 30,000.

In some Ontario parks, Parks Canada officials shoot cormorants to stem the loss of trees. Wildlife defence groups argue about a hierarchy of values in nature: Are trees and the forest canopy more worthy than a colony of cormorants?

These widely unloved, fish-eating migratory birds are ruthless nest builders. With their hook-tipped bills, they strip tree branches; their guano becomes a hyper fertilizer, wrecking the chemistry of the soil. Trees die three to 10 years after the birds build their nests.

On Lake Erie's tiny Middle Island, in Point Pelee National Park, 20,000 cormorants have stripped away 41 per cent of the tree canopy. To reduce the impact on the island's nature life, Parks Canada officials went out with small-gauge rifles for six days in April and May and shot 1,600 birds.

A cull is not proposed on Toronto's spit. "We don't feel lethal control is appropriate or needed," says park manager Ralph Toninger.

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