Organic modeling is tough enough with decent reference images. Without reference images to follow, just modeling from the odd photograph or two, is very difficult. It does get easier with experience, so, if you are determined to make a professional looking 3d arctic tern, my suggestion is to put this project on hold and get some experience. Do some modeling tutorials, learn how to get the shapes you want into three dimensional virtual space.
Then, when you have the basics mastered, go back to those bird tutorials and they will make a lot more sense.
Otherwise, you might wind up like old lexi, here, who has been plugging away at his idee fixe for over a year now. You’ll notice I gave him the same advice I’m giving you. You might also notice he didn’t take the advice. Take a look at the last page of his thread. Is this where you want to be with your bird a year from now?