Necessities aside, what do you carry with you on a field trip?

Some years ago, I was doing research of waterbird migrations with a young ornithologist friend of mine. A knowledgeable birder and great company, he was able to forget just about everything. On several occasions, he lost some screws and minor parts of my tripod en route (he couldn’t believe that and even accused me of deliberately hiding the screws), on others, he forgot to take his binoculars with him (“Why does it matter, you’ve brought the scope, haven’t you?”). More than once, I’ve suggested to him that he puts a checklist on his front door, so he can tick what he has taken and realise what he hasn’t: binoculars – tick; field guide – same as the spotting scope, most of the time he counted on me to carry this; your own head – ouch, I’ve forgot it! Trust me – he was capable of forgetting his head.

This brings me to the topic: my own non-necessity checklist. A morning or a day trip, I mean – not an expedition. For example, when I’m birding alone, I rarely carry snacks – being outdoors, I am satisfied with air alone, it seems. But if someone next to me starts eating, that ruins the air-factor and then I do carry a sandwich or so… Also, if temperatures aren’t very high, I carry a minimum amount of water – barely enough for a sip or two before I use the rest for instant coffee.

Here it is – my non-necessity checklist:
• Swarovski BP Backpack 30 – they thought of everything: from those scope straps inside to a very simple and elegant tripod-carry system, and from the upper pocket for your binoculars (so it does not end at the bottom and get hit every time you put your rucksack on the ground) to the air ventilation system along your spine and the hard bottom (to protect everything from hard blows).
• Summer quail hunting vest – 6 pockets in the front, 3 on top of each other, in combination with breathable fabric.
• Mobile phone – for eBird, Merlin, also towing and similar assistance calls.
• Water canteen – used to carry a smallish Sigg, size for two coffees, but since recently a thermos flask 0.4 litres (not so good for warm liquids, but keeps the cold water nicely fresh all day).
• Instant coffee bags – I usually keep several in my backpack.
• Chocolate bar (if the weather is not too warm) or a sandwich.
• Victorinox Soldier 2008 – one of those larger models with lock blade.
• Gardening kneeling pad – for sitting, perfect size.
• Insect repellent spray – so I could spray it over my trousers and socks against ticks (I do not mind a mozzie or two… ok, more than a few dozen mozzies do tend to bother even me).
• Sun block and lip balm – when I do not forget it…
• Toilet paper and wet tissues – self-explanatory.
• Matchsticks and/or lighter – I do not smoke, and never had to use it on a birding trip, but I do remember capsizing a kayak and like to have it, just in case. 

Absolute necessities aside, what do you carry with you on a field trip? What’s on your list?