The swan population in St. John's has grown from two to 10 in less than seven years. ((CBC))

City workers in St. John's are taking steps to keep the provincial capital's burgeoning swan population in check by sabotaging the birds' eggs.

Two swans were introduced to Bowring Park, in the city's west end, seven years ago.

Now, there are 10 swans on four different ponds throughout the city.

The director of public works, Paul Mackey, said St. John's has to make sure the swan population doesn't get out of control.

To that end, city workers are sneaking into nests and coating swan eggs with vegetable oil, which keeps them from hatching.

"The swan will continue to sit on the eggs for a period. When they don't hatch, the swan will abandon the egg and just carry on," Mackey said Friday. "You can take the eggs, obviously, but what happens [is] they will just lay more."

Mackey said the vegetable oil method means the city doesn't have to resort to neutering the birds.