Birds are a group of warm-blooded vertebrates constituting the class Aves , characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5.5 cm (2.2 in) bee hummingbird to the 2.8 m (9 ft 2 in) common ostrich. There are about ten thousand living species, more than half of which are passerine, or "perching" birds.
Birdwatching, or birding, is the observing of birds, either as a recreational activity or as a form of citizen science. A birdwatcher may observe by using their naked eye, by using a visual enhancement device like binoculars or a telescope, by listening for bird sounds, or by watching public webcams.
Most birdwatchers pursue this activity for recreational or social reasons, unlike ornithologists, who engage in the study of birds using formal scientific methods.
Birding in North America was focused in the early and mid-20th century in the eastern seaboard region, and was influenced by the works of Ludlow Griscom and later Roger Tory Peterson. Bird Neighbors (1897) by Neltje Blanchan, an early birding book, sold over 250,000 copies. It was illustrated with color photographs of stuffed birds.
The organization and networking of those interested in birds began through organizations like the Audubon Society, which was against the killing of birds, and the American Ornithologists' Union (AOU). The rising popularity of the car increased the mobility of birdwatchers and this made new locations accessible. Networks of birdwatchers in the UK began to form in the late 1930s under the British Trust for Ornithology (BTO). The BTO saw the potential to produce scientific results through the networks, unlike the Royal Society for the Protection of Birds (RSPB) which like the Audubon Society originated from the bird protection movement.
Like the AOU in North America, the BOU had a focus mainly on collection-based taxonomy. The BOU changed focus to ecology and behaviour only in the 1940s. The BTO movement towards 'organized birdwatching' was opposed by the RSPB, which claimed that the 'scientification' of the pastime was 'undesirable'. This stand was to change only in 1936 when the RSPB was taken over by Tom Harrisson and others. Harrisson was instrumental in the organization of pioneering surveys of the great crested grebe.
Increased mobility of birdwatchers ensured that books like Where to Watch Birds by John Gooders became best-sellers. By the 1960s air travel became feasible and long-distance holiday destinations opened up. By 1965, Britain's first birding tour company, Ornitholidays had been started by Lawrence Holloway. Travelling far away also led to problems in name usage: British birds such as "wheatear", "heron" and "swallow" needed adjectives to differentiate them in places where there were several related species. The falling cost of air travel made flying to remote birding destinations a possibility for a large number of people towards the 1980s. The need for global guides to birds increased, and one of the biggest resulting projects was the Handbook of the Birds of the World, begun in the 1990s by Josep del Hoyo, Jordi Sargatal, David A. Christie, and ornithologist Andy Elliott.
Initially, birdwatching was largely restricted to developed countries such as the United Kingdom and the United States of America. Since the second half of the 20th century an increasing number of people in developing countries have engaged in this activity, such as in the Degua Tembien district of Ethiopia. Transnational birding has played an important role in this, as birders in developing countries usually take up the pastime under the influence of foreign cultures with a history of birding. A majority of transnational birders are middle-aged, male, affluent, and belong to the Anglophone countries or Scandinavia.
