Between March of 2006 and October of 2007 BBC Wildlife Magazine had a feature they called Photo Masterclass in each issue. The essays covered a variety of topics, from photographing plant life to capturing animals in their environment to dealing with the challenges and rewards of shooting at sunset and sunrise.
Each feature has contributions from a number of professional photographers. They offer tips and stories related to the main theme for that particular feature, and there are plenty of example photos to drive the points home.
The series is hosted by Mark Carwardine, a world renowned zoologist, conservationist and wildlife photographer. Most recently he worked with Stephen Fry on a series for the BBC called Last Chance to See where he and Fry travelled the world seeking out endangered species. He's definitely an authority on capturing nature on film. You can read more about him and see his work here: http://www.markcarwardine.com/.
The PDF versions of the features can be downloaded from this website: www.bbcwildlifemagazine.com/masterclasses.asp