White Geese, or Swans?

On "SE 448 SE" (that's what the sign said) today, west of town, I stopped to see something in a stubbled field. At first I thought they were swans, so huge were they. There were two white, and two light tan birds -- two couples. The white ones looked much larger than Canadian geese, the size difference making them seem swan-like. Geese, or swans?