A CTV News investigation has discovered that bird deaths in tailings ponds are higher than the public is led to believe.

"The reports we have are the duck incident is not an isolated one. Ducks and other life are constantly being taken by these tailings ponds, even other animals are reported in the area, drinking from these lakes," says Mike Hudema, a spokesperson for Greenpeace.

Last spring, about 500 ducks died after they landed on a tailings pond owned by Syncrude.

The company said it was a one-time occurrence but documents obtained by CTV News, under access to information laws, show birds have been dying there for decades.

In an email exchange with colleagues after last spring's incident, an Alberta Environment employee says, "Typically, at the Aurora site, between 2-23 birds are oiled each year (self-reported by the company) In the 1980's and 1990's between 50-70 birds a year were reported being oiled."

The ongoing harm to wildlife has prompted Ecojustice to take Syncrude to court.

The non-profit organization is using an obscure provision of the criminal code that allows private prosecution. "Three months from now, birds will be migrating back into the Fort McMurray area and nothing has changed...it's time this government moved forward in a timely matter," says Barry Robinson from Ecojustice.

On Tuesday, the government did release new guidelines for tailings ponds which the Energy Resource Conservation Board says will give them more power to enforce the rules.