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Cormorants are colony breeders, building several nests in a single tree

Cormorants are not charismatic birds.  Though they’re precision fishers who dive for their prey like sleek, black jet fighters, they nest in trees and foul the ground beneath them with excrement and urine.  Cormorants are also apt to regurgitate when startled.  And over time, the sheer volume of cormorant guano on a Lake Erie Island rookery will alter the make-up of the soil, making it so acid that trees and other vegetation die.

Cormorant populations – once nearing extinction because of DDT – are now so prolific in the Great Lakes that they can kill ecosystems that many natural resource and park managers have vowed to protect.

That’s why officials on both sides of the US-Canadian border have been culling the animals in recent years.

Since 2006, U.S. Fish and Wildlife and ODNR biologists have employed sharpshooters to kill hundreds of nesting pairs of cormorants on West Sister Island and two other islands in western Lake Erie.  And this year, Parks Canada has launched its second year of cormorant culls on uninhabited Middle Island, just south of Pelee, a popular summer tourist destination.  Middle Island was acquired by Ontario about ten years ago to extend what in Canada is a rare Carolinian ecosystem of deciduous plants, including the Kentucky coffee bean tree.  Park officials are mandated to protect that ecosystem, but not the birds that have taken over the island.

Stepping foot on an island where cormorants have taken over is an eerie experience.  As you approach, hundreds of the birds – male and female – who guard the nests fly up and wheel around the sky.

Cormorants wheel in agitation as our Lake Erie research boat nears their rookery on East Sister Island.

The smell of the guano hits you 20 yards offshore.

In early May, the remaining forest canopy is not fully leafed out.  Goose-necked black cormorants peer down from their nests in the crooks of trees sixty feet above you and utter sounds like a person vomiting. The forest floor is spongy with their droppings and downed tree limbs – cormorants are ungainly fliers who knock off branches when they land.  Guano covers tree trunks and the few ground plants that survive.

This is not a place for humans.  Yet small purple flowers appear in the gloom and a few other bird species – Great Blue herons and terns and gulls – manage to co-exist.
Some wildlife biologists and cormorant advocates will tell you that what natural resource and park managers call an over-abundance of cormorants is normal.  They point out that in the Great Lakes, cormorant rookeries have taken over less than one percent of the 30,000 islands that dot the lakes.  They’ll also tell you that humans have never let cormorant populations reach a natural balance before deciding to reduce their numbers.   The controversy over culling cormorants is an international one that is unlikely to be resolved.

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