Yup, indeed, survival of the fittest and all that. The problem for evolution though is how does a creature become more fit by exchanging its forelegs or arms for wings when it cannot yet fly? The question is how the many changes required for making a bird a viable flying organism could have all taken place while making the species undergoing the changes more viable at each step. These are the questions which evolutionists always fail to answer and which they are totally unable to answer. In fact they are not even able to state the order in which the many different features of birds could have arisen (let alone show any evidence for such an order of transition). Again this is quite interesting since large transitions should have the most evidence for them.