Mike Atkinson Bird Photography Tutorial 7:  Basic Field Techniques
http://mikeatkinson.net/tutorial-7-basic-field-techniques.htm

Fred Miranda’s site with technical information on Canon and Nikon and much more
http://www.fredmiranda.com

Bird photography for experienced photographers
http://www.birdphotographers.net/

Digiscoping advice
https://www.birds.cornell.edu/AllAboutBirds/gear/Digiscoping/
https://www.bhphotovideo.com/explora/photography/tips-and-solutions/guide-birding-and-digiscoping