ECOLOGICAL ASPECTS OF ADAPTIVE RADIATION IN BIRDS

摘要: Summary 1. Relatively few birds feed heavily upon green-plant materials, though a number may take substantial numbers of buds. Birds appear not to possess adequate gut biota break down cellulose efficiently, and even it they did, this system would be compatible with efficient flight, on account the long processing times required. 2. have stronger adaptations toward feeding seeds make particularly heavy impact in trees those widely scattered or unpredictable crops. 3. Several families, mostly tropical distribution, primarily fruit. Again, are most successful exploiting resources reached only difficulty by other groups. A similar pattern holds for nectar stores. In case fruit nectar, evolutionary complications result because plants compete seed dispersers pollinators. 4. Most herbivorous species their young partially totally insects animal foods. Only able fledge an entirely diet, that do so often extremely fledging periods, which subject high rates predation unless parents nest places inaccessible predators. 5. general, relative animals when exploit groups obtaining (hard reach, space and/or time). 6. Insects exploited more families than any food category. greatest importance capturing wing arboreal locations. Other terrestrial invertebrates probably taken techniques used insects. 7. variety invertebrate prey along water's edge shallow water. 8. Almost without exception, vertebrate is small size, part function size birds. Occasionally vertebrates relatively heavy, generally outbreak situations. 9. exclusively fish, crustacea, squid, aquatic prey. Some indirect evidence suggests exploitation these sometimes there little appreciable source. 10. among important scavengers remains. 11. Like birds, carnivorous exert hard reach time. 12. One-third avian regularly resources, as recognized Table I. specialize located certain areas (ground, edge, trees, etc.). 13% use such wide range foods transcend both considerations (food type, segment habitat). very cases (5 %) does designation from some family specializing one category others using different category. 13. There been large (> 20 kg), several omnivorous species. Large rarer. All flightless, occurred where mammals were scarce absent. 14. made limited subterranean areas, caves, deep water, facilitating types life virtually incompatible success situations. characterized rapidly decreasing gradient. 15. Bats certain, but all, The bats available over full 24 h period; thus, bats' nocturnal habits provide them advantage them. 16. also With exceptions, smaller bats. Considerable consistent argument segregation time, resource flying at least caused competition. 17. While selection anti-predatory mechanisms can surmised, reciprocal density relationships frequently noticed between organisms suggest arise competition, rather predation. 18. information interactions same trophic level usually, invariably, food. 19. relationship existing described above repeated groups, clearly ubiquitous kingdom.