The fossil record does not support the idea that evolution happens slowly over long periods of time. You need to go back to school and learn about punctuated equilibrium. Darwinists now claim that evolution happens quickly after long periods of equilibrium, so yes the non-vultures would have to have become vultures quickly, because that's the only way it possibly could have happened without leaving any fossil evidence of this alleged transition. Darwinists are always having to change their theory because the evidence is always proving Darwinism WRONG. That's why you don't want to defend the idea of universal common descent, because even you know that there is no evidence to prove such a preposterous idea. So now you want to blur the distinction between natural selection and speciation, in order to muddy the waters and cause confusion, because people will only believe in Darwinism if they are confused about how it is supposed to work. I am not confused about how it is supposed to work because I studied biology and biological anthropology in college, so I know exactly how evolution is supposed to work. The more I came to understand the theory of evolution, the less I believed it. You want everyone to just accept your theory uncritically without thinking about it, because that's the only way you can fool people into believing that it's true.
Swiftly in evolutionary terms is still hundreds of years. So you are contradicting yourself again!!!! First you say that common descent is assumed based on looking similar. Wrong. Then you say old and new world vultures look the same because they made similar adaptations to similar environments. Then you contradict yourself and say they were always vultures and would not change. And now you contradict yourself AGAIN and say it had to happen quickly!
Wow are you ever ignorant and confused.