Photographers trying to get shots of the nesting birds on Inner Farne in the Farne Islands, and avoid getting dive bombed by Arctic Terns. Although I have a fairly long 28-300mm lens, it is nothing compared with these massive lenses. I can imagine it would weigh a ton having to cart these around, and personally I think I would prefer to travel comparatively light. However, it must be worthwhile as you can probably get some good close shots with these.