These are some of the research tools I currently use. I’m sure this list will continue to grow so I will update it regularly.
Stefan Buczacki, Fauna Britannica, Hamlyn, London, 2002.
Mark Cocker and Richard Mabey, Birds Britannica, Chatto & Windus, London, 2005.
Richard Mabey, Flora Britannica, Sinclair-Stevenson, London, 1996.
Pat O’Reilly, Fascinated by Fungi: exploring the majesty and mystery, facts and fantasy of the quirkiest kingdom on earth, First Nature, Rhydlewis, 2011.
Francis Rose, The Wild Flower Key: How to identify wild flowers and shrubs in Britain and Ireland, revised and updated by Clare O’Reilly, Penguin Books, London, 2006.
Paul Scofield and Brent Stephenson,Birds of New Zealand: A Photographic Guide, Auckland University Press, Auckland, 2013.
Paul Sterry, Collins Complete British Wildlife Photoguide, HarperCollinsPublishers, London, 1997.
Paul Sterry and Barry Hughes, Collins Complete Guide to British Mushrooms and Toadstools, HarperCollinsPublishers, London, 2009.
I have also have several of the excellent keys published by the Field Studies Council, see website below.
Amanita Photo Library: http://www.amanita-photolibrary.co.uk/
British Bugs: http://www.britishbugs.org.uk/index.html
British Dragonfly Society: http://www.british-dragonflies.org.uk/home
British Leafminers: http://leafmines.co.uk/
British Lichens: http://www.britishlichens.co.uk/
British Mycological Society: http://www.britmycolsoc.org.uk/
British Trust for Ornithology: http://www.bto.org/
Diptera Info: http://www.diptera.info/news.php
Field Studies Council: https://www.field-studies-council.org/
First Nature: http://www.first-nature.com/
Floral Images: http://www.floralimages.co.uk/default.php
Hidden Forest: http://www.hiddenforest.co.nz/slime/index.htm
Mushroom Expert: http://www.mushroomexpert.com/
Mycenas of Northern Europe: http://www.mycena.no/
Nature Spot: http://www.naturespot.org.uk/home
New Forest Fungi: http://www.newforest.com/
Plant Life: http://plantlife.org.uk/
UK Butterflies: http://www.ukbutterflies.co.uk/
UK Moths: http://www.ukmoths.org.uk/
Wildlife Insight: http://www.wildlifeinsight.com/
The Wildlife Trusts: http://www.wildlifetrusts.org/
Woodland Trust: http://www.woodlandtrust.org.uk/