Worth to duplicate this from a
Youtube comment to here:
"1) Why don't you take me step by step how did the dinosaur became a bird . Please include all the fossil evidence"
I refer this to the answers to questions #2, 3, 4 and 5, but since you wanted fossils, here are a few:
Incusvasaurus, caudotheryx, Avimimus, Microvenator, Chirostenotes, Anzu, Protoaechaeopthery, Similicaudipteryx, Caudipteryx, Oviraptor, Citipati, Wulatelong, Khaan, Conchoraptor, Ajanciengenia, Heyuannia, Talos, Sinorhithoides, Gobinvenator, Troodon, Zanabazar, Mei, Byronosaurus, Confuschis, Microraptor, Epidexipteryx, Scansorioptery, Yi, Wellnhoferia, Jeholornis, Sapeornis, Confucisurnis, Yanoris, Balaur, Microraptor, Velociraptor, Buitenraptor, Sinornithosaurus, Protachera, Anchiorni, Jinfengopteryx, Sinovenator, Archaeopteryx, Paracoracias.
To mention a few I know of, but there are several hundreds, if not thousands, of them if you want more....
"2) How many physiological changes it needs to go through to turn into a bird?"
I am not an expert, but I would say 3.
But it depends on what you prefer to call a bird or bird like, most bird features are already present in Eumanorpatoria (including flight), so lose of teeth and tail and fusing the finger digits is all that is needed to be classified as a true bird, all the other bird characteristics was already present in dinosaurs since at least theropods, if not earlier.
If you saw a Oviraptorosaur today such as Avimimus you would confuse it and its behavior with a bird, but it isn't a bird far from. If you saw a Troodontid such as Anchiornis or Dromaeosaur such as Microraptor, you would swear it was a bird, but it isn't. Birds does not have three fingers, tails, teeth and four wings.
Oviraptorsaurs, Troodontids and Dromaeosaurs are not birds, even thou they look like birds to us, they are variation of feathered dinosaurs. Just like birds is another variation of feathered dinosaurs.
"3) How many changes in behavioral traits needs to developed to turn into a bird."
Nothing. They was already present in dinosaurs.
"4) How these changes were seamlessly administered without guidance?"
Not sure what you are asking about, but based on fossil evidence, it seams to be no plan at all, but every possible wired combination you can think of seams to have been tested out by evolution and it just so happen that the present form of feathered dinosaurs (dinosaurs with no teeth and tail, and fused fused finger digits) are the one that remains. I would not call the evolution of birds "guided" but more like a coincident ,that what we today call, birds happens to be the one group of all wired combination that survived.
"5) How many years did each step to be completed?"
They were already present in dinosaurs so they did not had to take any timer to be "completed" in birds since they already was there. You seams to think the step from dinosaurs to bird is a big jump of some sort, but it isn't, it was very gradual and smooth. A bird is a dinosaurs and what you call "bird features" and wonder how they evolved is actually dinosaur features. Birds are dinosaurs, because they have dinosaurs traits, birds never evolved from dinosaurs into bird - they have always been dinosaurs and still are, they are just a variation of dinosaurs (avian dinosaurs - compare this with avian mammals such as bats; you don't ask when bats evolved from mammals to bats do you, because you know they ARE mammals, don't you?). When you look at a bird today, that is pretty much how dinosaurs looked like back then as well (just like a bat looks like AND IS a mammal). Therefore "bird" traits never had to evolve in birds, just as bats never had to evolve mammal traits, because the traits was already present for hundred of millions of years before birds even existed.
What you like to call a "bird" is not an absolute things, but a matter of subjective definition. I refer this back to my answer of question #3.
