Haha, that's a pretty good article. They're right that state bird designations are repetitive and uncreative when states could use them to recognize birds that are unique or special to their history.

I'll note, though, that the cardinal family of birds includes quite a few different names. For example, the many kinds of tanagers, grosbeaks, and buntings are cardinals. So is the dickcissel. See https://en.wikipedia.org/wiki/Cardinal_(bird) for example.

Thus the Slate article is suggesting replacing most of the Northern Cardinals with cardinals-by-another-name. There's no indication they're aware they're just swapping names.