There is nothing missing. If you wanted to add a word to make it clearer, it would be 'on'. "The sky was blue and clear on the morning she was ready to come out and open her beautiful new wings." 'The sky was blue and clear' is the main part of your sentence. ' (on) the morning she was ready to come out and open her beautiful new wings' is extra information.

The sentence is grammatically correct, however to dispel ambiguity and so as to not cause confusion to your audience when could be used.