Geese prove how silly taxonomy has become. In reality, a few of the species in the genera Anser & Branta should probably be combined under
Anser anser. The traditional separation was based on colour.
The last I heard, it was definitely established that some of the Anser 'species' are fully interfertile, produce fertile offspring, & readily breed when they meet. Nobody knew if greylag/canada goose hybrids are fertile, & nobody was trying to find out. It was generally assumed that because they'd been classified in different genera, they'd be infertile.
I hope that one day, sanity breaks out among taxonomists, but I won't hold my breath. I think that they're determined to classify as many species as possible because that's how you get your name in books.
