Tar sand mining sites can be treacherous for birds. For one, the birds can’t tell the difference between clear water and tailings ponds tainted with bitumen and other toxic mining byproducts. Thirty Great Blue Herons may have learned this the hard way last week when their bodies were discovered at a mining site in Alberta, Canada. The exact cause of death is under investigation, and the broader practices of the mining company, Syncrude, one of Canada’s largest oil producers, are under scrutiny. Birds that land on exposed tailings ponds at mining sites can be harmed or killed if they ingest the oil while cleaning their feathers. The oiling also makes the birds more vulnerable to hypothermia and affects their buoyancy, which puts them at greater risk of drowning. Employees at Syncrude found the dead herons near a pump house that’s used to keep oil sand slurry flowing smoothly through pipelines, said company spokesperson Will Gibson. The only bird found alive, but...