simple magnet test would work...
Please show me the box your ammo came in sir. Reloads? Please open one.
A magnet will prove it's steel shot. Bismuth, if you can find any, will be more difficult.
Unless the province specifically states that the POSSESSION of lead shot while hunting migratory birds is illegal it would be hard to get a conviction on a charge of possessing lead shot. The Federal Regs prohibit its USE not having a few grouse loads in your pocket. Alberta also prohibits its use while hunting waterfowl but not its possession.
Do they have something that would detect lead?
The possession of lead while hunting waterfowl is prohibited all across North America, it is a complete ban. And if your walking to your blind with lead shot in your pocket, you had better be carefull, it is a chargeable offense to be in possession of lead shot within 100 m of any water way.