A History of Birdwatching in 100 Objects

Wallace’s early map of the zoogeographical zones of the Earth has changed little in the interim, and the regions described still assist in understanding how and why animals are distributed around the planet in the way they are. They also help birders set limits to their listing.

Birders love lists, and are particularly fond of keeping lists for geographical areas, whether on a local or global scale. For those able to travel beyond the borders of their own countries, lists are usually kept on the basis of the zoogeographical zones of the world.

These zones are generally accepted by biologists as logical and accurate ways of physically dividing the Earth’s animals and plants into separate geographical and evolutionary lineages and histories. More precisely, those regions can be defined by their biotas, which in turn reflect the geological and spatial separation of those regions.

Alfred Russel Wallace (1823-1913) is perhaps best known as biology’s ‘nearly man’ – he came up with his own theory of evolution simultaneously with Charles Darwin, and it was Wallace’s determination to publish his work that forced Darwin into publicly revealing what popular history sometimes forgets was actually more of a joint presentation of both scientists’ work. Wallace independently came up with the idea of natural selection as a driver of evolution, and remained a die-hard defender of this idea, but was also forward-thinking enough to consider environmental influences as important as, or even more so, than the inter- and intra-species competition that Darwin cited.

Encouraged by contemporaries including Darwin, Wallace also began his life’s research into the distribution of the various types of animal around the globe, getting into his stride in 1874 after more accurate taxonomies had been devised. Factoring in the contemporary belief in land bridges (this was before the continents were known to drift on their crustal plates), as well as glaciation, geographical barriers like oceans and mountains, and the vegetation zones of the planet, he was able to map the major biotas of the Earth by summarising the known distributions of genera and families of animals, the majority of which had already been discovered by the time he was writing.

The resulting book, The Geographical Distribution of Animals (1876), would remain the standard text until at least the Second World War, and put names to six of the eight biogeographical realms (also termed ecozones in modern publications) which are in use today: Nearctic (most of North America into Mexico); Neotropic (essentially Central and South America and the Caribbean); Palearctic (Europe, North Africa, the Middle East and Asia north of the Himalayas); Ethiopian (now known as Afrotropic, covering sub-Saharan Africa and Madagascar); Oriental (or Indomalayan, covering the Indian subcontinent and South-East Asia); and Australian (Australia, New Guinea and associated islands). The two additional realms are Antarctica and Oceania. Each of these has a distinct fauna and flora – and avifauna – with many more endemic forms than cosmopolitan.

With refinements, these zones remain pretty much intact today, and one of the greatest refinements was named after the great man himself: Wallace’s Line. On his extensive travels in Indonesia, he noticed a clear transition between the faunas of Australia and Asia across the distance of the Lombok Strait between the islands of Lombok and Bali, only 35 miles apart at their closest. This deep water barrier extends north between Sulawesi and Borneo, and remains a clear faunal divider along its whole length. We now know that the barrier remained intact even when glaciation was at its height, greatly increasing the area of the adjacent land masses.

The Palearctic region is commonly separated into Western and Eastern subregions, using the Ural Mountains as the dividing line in tune with the principles laid down by Wallace almost a century and a half before. In this way, his contributions to zoology and evolutionary theory are unwittingly commemorated when every birder ‘ticks off ’ a new species on their ‘West Pal’ list.