Ecology and the environment

Nature, natural history and ecology; practical environmental techniques, habitat management.

What are your favourite books for identifying animals, plants, birds, insects, fungi, etc.?
What are your recommendations for aids to habitat surveying, creation and monitoring?
What's so good about these ones?

Please indicate what part of the world your books relate to (for obvious reasons).

Books are likely to be found under the following tags:
natural history, nature, conservation, ecology, field guide, botany, plants, ornithology, birds, entomology, insects, zoology, animals, mycology, fungi, taxonomy, habitat, ecosystem, survey, wildlife, biodiversity, etc