Think of the dodo as a baby harp seal with feathers. I know that's not even close, but it saves time.Waldrop's tale is very straight forward and depends on the lightest touch of alternate history or might-have-happened to produce his effects. "The Ugly Chickens" might fit loosely alongside Ballard's Drowned Giant. Combined with the very slight tone of humor and the headlong pathos of the narrator, the reader is left to ponder the many slight revelations along the way, somehow coming away with a sense of distant sadness exactly appropriate to its subject. Masterful.
Read it online here for free. (Update: looks like the folks took the page down; no doubt the volume of estimable readers of Black Gate swamped them! Unfortunately, can't find it anywhere else. Given the subject matter of the short story, I suppose it is ironically appropriate).