In “Sibley’s Birding Basics”, Sibley describes primary projection as extension of the primary tips past the tertials. A couple of paragraphs later, he describes this measurement for which you want a term, but gives it no name.
This is in a 13 page chapter just on wing structure, so you’d think he’d mention the term if there was one.
But I’ve heard the term “tail projection”, and assumed it meant wing tip to tail tip. What’s the definition of that?
Peter Shute