If you live in a part of England famous for its rare and interesting bird life, as I do, some sort of acquaintance with the birdwatching fraternity is taken for granted. Its adherents appear at all seasons and in all weathers, toting telescopes and tripods across a windswept marsh or field. They are not exactly solitary figures, but, unlike ordinary country ramblers, they seem self-contained and detached, absorbed in their private quest. Although anyone who loves country life takes pleasure in the sight and sound of the birds of the air, these specialists convey a different kind of appreciation - innocent enough, surely, but slightly mysterious too.

This fascinating book by Jeremy Mynott explores many aspects of this and related matters. He explains some of the birdwatcher's obsession in a rather unexpected way, by recalling a familiar scene in the Louvre. A great crowd clusters excitedly around the Mona Lisa, all facing more or less towards it but many of them looking at it through the viewfinders of their cameras or mobile phones. After inspecting the results they move on quickly to the next highlight on their itineraries. They are clearly all very keen to have seen the Mona Lisa but they don't actually want to look at it very much. What they want is a souvenir to confirm the occasion and to add to their collection.

Much the same, it seems, is true of the dedicated birdwatcher. He is above all devoted to the compilation of his List or Lists of birds seen and identified. Typically, he has a lifelong list, another list devoted to a particular place or country, a local list, and so on. He is satisfying an enduring human urge to classify and impose order. After all, some of the earliest surviving texts are essentially lists, for example the Linear B tablets of palace records in ancient Crete.