Birdwatching from our living room. Our new living room, that is: as we moved from Brisbane, CA to Ann Arbor, MI, our new home has a wooded backyard, some large trees and undergrowth, small creek included. At first sight I was sorry for one dead tree but then I realized that it improves our birdwatching.
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For centuries, birds have been the most pursued and best known of all animals, but here again new species are still coming to light at a steady pace. From 1920 to 1944, the golden age of ornithological field research, an average of about ten subsequently authenticated species were described each year. The number dropped to between two and three and remained steady thereafter into the 1990s. By the end of the century, approximately ten thousand valid species were securely established in the world register. Then, an unexpected revolution in field studies opened the census to a flood of new candidate species. Experts had come to recognize the possible existence of large numbers of sibling species - populations closely resembling one another in anatomical traits traditionally used in taxonomy, such as size, plumage, and bill shape, yet differing strongly in other, equally important traits discoverable only in the field, such as habitat preference and mating call. The fundamental criterion used to separate species of birds, as well as most other kinds of animals, is that provided by the biological species concept: populations belong to different species if they are incapable of interbreeding freely under natural conditions. As field studies have increased in sophistication, more such genetically isolated populations have come to light. Edward O. Wilson: The future of life, Alfred A. Knopf, New York, 2002. |
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