I have found that, on the whole, birders are very fond of food. Trenchermen to a man (or woman). Never ones to refuse a proffered bite. Unwilling to forgo an offered cuppa. Greedy so-and-so's, actually. But they are all different in what they do to ensure that the time in the field is not spoilt by rumbling stomach noises and possible nutrition depravation...
I used to be a sandwich and thermos flask birder. Maybe an apple or banana as back up (never an orange, what with sticky juice and zest to gum up optics and making your fingers tacky to the point of being a hazard). One chap that I spent a lot of time with in the early 1980s (the late Mike McDonnell) used to go to town with his lunchtime snack - he owned a giant thermos flask that he used to fill with sausages, pork chops, chicken thighs and other tasty off-cuts of meat. These were joined by quiches and bread rolls. Give him his due, he used to let us 'peanut butter sandwich' boys have some of his superior eats.
There were others who never brought pre-prepared food on a big day out, but relied on a shop (or a pub) to be (a) open and (b) in the area that we were birding in. This could be tricky when in the middle of nowhere or slogging our way along an exposed headland. Many the time has a birding chum abandoned the hunt for the rarity to walk the mile back to the car to then go in search of food.
Coffee was my hot drink of choice, ready made in the thermos (no need to fanny about with adding milk as it was already there!) but I have witnessed others having only hot water in the flask, with a small jar of coffee, a plastic container of milk and a teaspoon being produced from a rucksack. Too much hard work! And I never made tea - it never kept well, always morphed into a tannin-loaded beverage just fit to be lobbed into the nearest bushes.
On a twitch we largely dispensed with the packed lunch (that was more of an 'out for the day casual birding' arrangement). Instead, it was food (can I call it that?) culled from stops at petrol stations and motorway services. The default setting for such times was a Mars Bar, can of Coke and a packet of crisps. If the twitch turned into a cross-country week-ender then not only were our diets morbidly inadequate it would turn the inside of the cramped car into a seething pit of belches and farts. Air fresheners, although sorely needed, were nowhere to be found.
During 1981-82 I went birding a lot with Bob Hibbert. Bob was another in the Mike McDonnell mould, whose packed lunch resembled a cross between a barbecue and a Fortnum and Mason's hamper. He always augmented my feeble sandwich with his copious left-overs and then insisted that, at the end of the day, I have a meal at his home (cooked in readiness by his wife) before he dropped me home. And believe me, the helping were enormous. I would finally get home, full to bursting, hardly able to waddle up the driveway, to be greeted as I opened the front door with the words, "Steve, your dinners in the oven..."