Well, I'm the kind that likes to have anything possible by hand. I usually wear one of those fisherman's jackets with thousand of pockets, all of them full with stuff, most of them used only twice a year: magnifying glass, pocket knife, GPS, pens, lens cleaners, field guide, bush hat, gloves, MP3 with birds voices, spare batteries, alcohol gel, insects repellent, camera accesories, etc. And for watching I put in the car everything and decide on the field what will I need.