So, you and your mates decide you'd like to produce a definitive photographic field guide to the birds of Britian and Ireland. You think about what's needed and ten years later, having sifted through a quarter of a million photos and enlisted one of the UK's top birders to write the text, it's finally out. Is it what you hoped? Is it what birders have been waiting for? Or are we all switching to apps, and is a new field-guide what's needed anyway? Andy Swash and Rob Hume give us their thoughts.'.