Common teal, eurasian teal, teal, singing teal...people love naming things and it takes plenty of effort to get everyone to agree on a name. Even when a name is agreed on, the scientific classification may remain disputed and murky, as in the case of the green-winged, common, and speckled teal clade. Above is a picture of two "species" within the super-species trio, green-winged teal and a surprise Eurasian teal. The story gets even more complicated as Speckled teal has been split into two separate species.
Check out this link to the American Ornithological Union, which has a committee dedicated to examining and deciding upon avian taxonomy and phylogenetics. The fact that it can be so difficult to define species sheds light on the perpetual march of life and that our naming and classification systems are excellent tools to aid in biological understanding, but they are not perfect tools.
And lastly, how are super-species different than subspecies? Well it has to do with vicariance and a few votes from a taxonomic committee.
