Still waiting for someone to explain how the first bird that was born as a DNA defect and of one sex happened to be across the pond of another with the same DNA defect changing making it a bird but of the opposite sex so they could propagate.
Transitions don't occur like that. First of all, "bird" is an arbitrary designation we apply to a fossilized animal when it bears a sufficient number of traits like what we know as modern birds. You can draw the line at different points in the fossil record, and many do, between "dinosaur" and "bird." That's because dinosaurs didn't really transition into something other than dinosaurs. It's just that a certain type of dinosaur is designated "bird" at the point in the fossil record when it is similar enough to what we know today as birds to be called that, and, as I said, different schools of thought differ as to what that point is.
Birds as we know them are actually just what's left of the dinosaurs. Most all of the categories of dinosaur became extinct, apart from what we know as birds.
Also genetic variations aren't defects. Each successive generation of any animal shows variation from previous generations. When the environment places a set of pressures on a species, this favors certain of those variations and disfavors others, causing gradual shift, eventually leading to changes such that we would characterize them as a different subspecies or a different species.
