as I said, it takes million years. And there are fossils of transition organisms, for example:Originally Posted by saibot
or more about transition of birds:
http://www.apus.ru/site.xp/049052056055 ... 53124.html
sorry, I have no time for searching in English, but you can have a look on pictures, without reading much Russian.
There is similar fossils for a lot of transition species.