Maybe I'm just not as persnickety as many folks here, but I think it is an amazingly beautiful photo! Birds have beaks, everyone knows that, and the "disappearance" into the dark underwing tones is a non-issue to me. You can still tell what and where the beak is! Perhaps minor cropping of the sky would help, but not much from my quick attempt.
Birds do not take direction well, so "Hey, you! Fly (higher, lower, in front of a better background will not "fly") pun intended!
A person could full auto the subject and hope go get better wing position, angle of view, etc, etc., but some days, in my never humble opinion...it is better to be lucky than good. Excellent effort and photograph!