Like most open spaces with lots of grass, our college campus is favored in migrating seasons by flocks of Canada geese.
To my eye all Canada geese look identical, down to the last feather, males and females too.
Yet they mate for life. It's fun to watch a happy couple meet after being apart and do their "Honey, I'm home" routine -- ahonk -- hink -- ahonk -- hink.
But if they all look exactly alike, how does a Canada goose recognize its spouse? Maybe they are monogamous because the grass always looks the same on the other side of the fence, so to speak -- the "no-temptation" theory of goose fidelity.
Or maybe relationships survive because the he-goose gets away with it. "Gosh, honey, I'm sorry. I thought she was you."