Here is a nice example of trentepohlia on the north side of a tree. This algae can be one of the best indicators of north if you know how to use it. Like all moisture indicators, including moss, it's important to understand the relationship between…

I was honoured to record Tweet of the Day for BBC Radio 4 recently. I chose the wood pigeon, more for its physical behaviour than its song. You can listen here. I remember feeling a bit surreal when doing the recording. It was about 3.30am…

My thanks to Malcolm Pinches for sending in these great examples of the 'wedge effect' from the Isle of Eigg in the Scottish Inner Hebrides. For a full description of this effect and how to use it to navigate see The Walker's Guide to Outdoor…