It might seem odd to find out that your birds and your oil come from the same place, but for many people this is true. Canada's tar sands, an enormous open-pit oil extraction operation located in Alberta, serves as one of the largest sources of oil for the US. But it also is located in a vital area for migratory birds, who have seen decreasing numbers. This backgrounder outlines how exactly tar sands development leads to loss of birds, estimated in the millions.