Birds, Biodiversity of

摘要: The life of birds is based on flight, which has both constrained their diversification and opened ecological opportunities. It affects size abundance. Their ecology the exploitation patchy variable resources, migration being most obvious manifestation this. A few are flightless. taxonomic diversity limited. Across all continents, bird species greater in wooded than forested habitats, generally related to habitat complexity productivity. Coexisting eat different foods often use parts habitat. Bird where there diversity; it less at higher altitudes; as one moves from tropics toward poles, with strong local modifications. may be correlated that other animals, but not always. data have been used test hypotheses about causes latitudinal gradient biodiversity. There evidence partly dependent tropical regions providing more opportunities, habitable area, utilizable energy. No found over world. Some closely replace each geographically. world, mainly tropical, unusually large numbers endemic, restricted-range species. Geological evolutionary history resulted avifaunas world differing richness origin. Unrelated living places similar habitats undergone convergence. Birds good colonists islands, they subsequently evolve presence (if any) land vertebrates. More larger those once formed landmasses, closer sources colonists. Islands become cut off mainland or fragmented lose because extinctions then sufficiently matched by colonizations. Humans caused extinction many birds, historical prehistorical times, especially islands. chief current threats them loss, hunting, agricultural intensification, introduction alien Reducing these will difficult. Avian biodiversity continues lost large-scale declines some without native ranges, diminishes differences communities lands.