Cormorant culls stabilizing Middle Island, Parks Canada says

After nearly a decade of annual cormorant culls, Parks Canada is close to stabilizing the number of birds taking up residence on Lake Erie's Middle Island, where their nesting and fecal matter threaten vegetation at Canada's most southern point.

The birds threaten the health of nine different species-at-risk on the island owned by Parks Canada. 

Six thousand nests were reported on the island — the southernmost point in Canada — when the cull began in 2008. As many as 25,000 birds would flock to the island each year, breaking branches, eating leaves, defecating everywhere and destroying rare Carolinian forest.

"Their guano that they deposit around their nests and in their nests … very quickly kills trees and vegetation," Tammy Dobbie, a Parks Canada ecologist said.

Middle Island's tree canopy decreased 45 per cent during 15-year period studied by Parks Canada.

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Today, the number of nests has been reduced to 1,794. A healthy balance between cormorants and wildlife can be achieved with about 1,100 nests on the island, according to Parks Canada. Middle Island is 18.5 hectares (46 acres) in size.

"There was a problem. Monitoring and research showed we were losing canopy at an alarming rate," Dobbie said. "We knew we had to take action really quickly if we were going to have these rare ecosystems and protect them on Middle Island."   

Parks Canada sharpshooters are responsible for killing the birds each spring. When the cull began, animal rights groups criticized the move, briefly getting an injunction stopping the first cull in 2008.

"The park claims the kill is necessary to save Middle Island's vegetation, but changes to the composition of vegetation are part of the natural process of succession experienced wherever colonial birds are found," Cormorant Defenders International says in a statement posted online. "The cormorants pose no threat whatsoever to the survival of any plant or animal species and Middle Island is one of the few locations available where cormorants can colonize."

But Dobbie said there were no other options. She said the island was dying and the cull provides a permanent solution to the problem.

"On Middle Island we've seen that we would have seen a devastating effect on the Carolinian forest, the ecosystem and the species-at-risk on the island," Dobbie said. "Just sitting by and watching through your monitoring programs the loss of biodiversity on the island and the loss of ecosystem health goes against what we're trying to accomplish."

Vegetation on the island is now beginning to come back, with promising levels of regrowth on inland portions of the island.

Dobbie said the decision to continue the cull will be made on a year-by-year basis.