Mapping tools - first to help with planning and getting a sense of scale, and then on the ground to navigate
Marking points of interest (POIs) - Goat Maps or Caltopo. Formerly Gaia GPS and Google Maps.
See below for field navigation towards POIs
Climate data, especially for precipitation and temperature. I've been using TimeAndDate (example is for southern Ecuador), Wikipedia's geography/climate sections of areas (which refer to local government resources), and the below Habitats of the World book is also good, but would love to learn about other resources for this information.
Travel advisories - consult multiple, as nobody has a monopoly on security information. These are often overcautious, even for me(!), but relative grades are informative.
Habitats of the World - by Campbell, Behrens, Hesse, and Chaon - fun book outlining the characteristics, geography, unique features, and key representative sites of all of the world's habitats. Great context.
Field guides - region-specific
Travel narratives, ideally nature-related, and/or immersed in the local culture.
Podcasts, especially Naturally Adventurous, that discuss the experience of visiting these locations, especially for nature travel, but also covering culture, food, logistics, etc.
Videos - a surprising number of people like to take video footage of their trips, harkening back to camcorder days. These can be a good way of getting a sense for a place. Do a YouTube search, and you may be surprised.
Some tour companies also put together video trip reports, or even 'virtual tours', see for example Tropical Birding's virtual tours that were presented during the Covid pandemic.
Want to upgrade to mirrorless in the near future, but keep balking at the cost! Especially as I don't adore photography on its own, and typically use it only as a documentation tool.
Spotting scope - Kowa (need to lookup the model, purchased sometime during the 2000s) + tripod
Maps
Field navigation towards POIs - Avenza Maps when a geo-referenced PDF for a particular site is available (ideal but rare), otherwise CoMaps. Offline map and POI access is essential for this. Formerly Organic Maps and Maps.me.
Identification
Sibley Guide to Birds app, for North America
Merlin app, for computer identification of bird sounds.
iNaturalist app, for computer identification of non-bird organisms.
Weather
Radar - I use MyRadar and Windy.com interchangeably, which both have good loops and resolution, but open to hearing about other alternatives.
Home office
Photo processing - Nitro for MacOS. Formerly its predecessor RAW Power, and earlier Adobe Lightroom, and Aperture.
My workflow in a nutshell - keep everything (no deleting), flag potential keepers, filter on those, crop, adjust exposure, adjust saturation if needed, done. Shouldn't take more than 30 seconds per photo. Backup all RAWs to external hard drive. Geotag keepers (either manually, or with GPS track taken in the field with something like the Geotag Photos Pro app), and upload to Apple Photos app which is synced with iCloud.
Sound processing - Audacity
eBird's audio preparation tips - I am less shy about applying high-pass filters for reducing background noise, but don't tell them that. At least I try to be relatively careful and conservative with it.
Scythebill - open-source listing software, can also track taxa like butterflies, reptiles, etc.
Birdstat - similar to Scythebill, more fun reports and visualizations