CALGARY, Alberta - Environmental groups took the first step on Wednesday to convince a court to charge Canada's largest oil sands producer with the deaths of 500 ducks, an incident that brought worldwide attention to the ecological impact of the huge energy resource.

Toxic tailings ponds, such as this one at Syncrude's Mildred Lake mine site, are an environmental challenge left behind after extraction of bitumen from the oilsands. (Photograph: Chris Schwarz for Edmonton Journal) Ecojustice, the Sierra Club and Forest Ethics want Syncrude Canada Ltd charged under the country's migratory birds act for the incident last April, in which the ducks were killed when they landed on a toxic tailings pond.

The green groups said they initiated the rare legal move after becoming frustrated with delays by the federal and Alberta governments, which launched investigations last year.

"We just think it should be prosecuted in a timely manner, especially given that three months from now we'll be into migration season and ducks will be flying back," Ecojustice lawyer Barry Robinson said. "If nothing has changed we could be risking the same thing."

Northern Alberta's oil sands are the largest deposits of crude oil outside the Middle East, and are seen as an important, safe supply source for the United States. But development is far more expensive, complicated and has much more environmental impact than conventional oil.

Syncrude mines the tar-laden sands in huge open pits and separates out the heavy crude using hot water and chemicals. The toxic waste residue gets pumped into the tailings ponds.

The company, a joint venture of Canadian Oil Sands Trust, Imperial Oil Ltd and five other partners, deters birds from the ponds with noise guns that simulate cannon blasts.

Syncrude said a late-winter storm delayed deployment of the sound cannons last April, and the ducks set down on the poisonous body of water. Deaths of waterfowl at such rates had never happened in three decades of operations, it said.

Under their legal action, Ecojustice and its allies have advised Alberta's provincial court in Edmonton of the charge they believe Syncrude should face under the Migratory Birds Convention Act along with some basic evidence.

The groups will present their evidence at a hearing on February 19, where they hope a judge will lay a charge, Robinson said. The maximum penalty is C$300,000 ($250,000), he said.

Syncrude spokesman Alain Moore said the company had not seen the documents, so could not comment on the legal matter.

"But this flock of waterfowl landing and drowning on our tailings pond last spring was an unacceptable incident and everyone in our organization feels horrible that it happened," Moore said. "There's tremendous resolve within Syncrude right now to make the appropriate changes to prevent this from happening again."

Last spring, the company took out full-page newspaper advertisements to apologize to Canadians.

But the incident only served to embolden environmental critics, who had already mounted global campaigns to highlight the impact of massive oil sands development on land, air, water and communities.

At the time, more than $100 billion of oil sands projects were either being constructed or planned, but oil companies have since delayed numerous plans as oil prices have tumbled.

Syncrude, located north of Fort McMurray, Alberta, is the world's largest oil sands producer, capable of pumping as much as 350,000 barrels of synthetic oil a day.

Its other partners are Petro-Canada, ConocoPhillips, Nexen Inc, Nippon Oil Corp unit Mocal Energy Ltd and Murphy Oil Corp.

($1=$1.20 Canadian)

(Editing by Rob Wilson)