The lawyer for Syncrude Canada is challenging the effectiveness of sound cannons to scare ducks away from toxic oil sands ponds.
The energy company is on trial on federal and provincial environmental charges over the deaths of more than 1,600 ducks in its Aurora tailings pond in northern Alberta two years ago.
Syncrude lawyer Robert White told court birds lose their fear of sonic cannons after about two hours.
He challenged the testimony of Todd Powell, an Alberta government wildlife biologist, who suggested ravens lose their fear of the cannons because they hear them so often.
But he added ducks usually leave an area and don't come back once they hear the cannons.
The Crown contends Syncrude was the only oil sands company in the area that didn't have noise-makers deployed on the day the flock of ducks landed on its tailings pond.