Birds as pollinators of Australian plants

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Abstract
Over one hundred species of birds have been seen visiting the flowers of some 250 species of plants in Australia. Honeyeaters and lorikeets are the most persistent flower‐feeders and some species depend almost entirely on nectar as a source of energy. Silvereyes, parrots, woodswallows, pardalotes, thornbills, and a few other species of passerines occasionally visit flowers. The genera most frequently visited are Eucalyptus, Callistemon, Banksia, Grevillea, Adenanthos, Dryandra, Epacris, Astroloma, Amyema, Correa, Xanthorrhoea, Anigozanthos , and Eremophila . Some flowers, e.g., those of Eucalyptus , are very generalised in structure and are visited and pollinated by insects as well as birds. Other plants have shown a range of adaptations to attract birds to their flowers or deter insects. Birds require significant rewards so that flowers must produce copious nectar. Rowers are often clumped into inflorescences (e.g., Banksia ) or individual flowers become large and tubular or gullet‐shaped ( Eremophila ). Flowers visited by birds are often red, though yellow ( Adenanthos ) and green (e.g., Amyema, Correa ) are common. Hairs in tubular flowers, and lack of attractive smell may deter insects without affecting birds (e.g., Astroloma ). In Australia the relationships between birds and plants are not as specific as those shown for hummingbirds and some of their flowers in tropical America. Most species of birds visit a wide range of plants, and most plants are visited by a wide range of birds. Pollen is usually placed on the forehead, face, and chin feathers of the bird or on its beak. Birds have been proved to be effective pollinators of many plants in temperate Australia. Little work has so far been carried out in tropical Australia. Bird‐pollinated flowers have mostly originated from insect‐pollinated flowers though it is possible that some (e.g., Banksia ) were, or still are, pollinated by mammals. It is not clear why so many of the dominant plant genera in temperate Australia are pollinated by birds. Birds may be more reliable pollinators than insects when the climate and flowering season are unpredictable, or during winter when many of the specifically bird‐pollinated plants flower. Birds may also increase the chance of outcrossing as they fly further between plants than insects. Nutrients are often limiting in Australian ecosystems, whereas energy rarely is. Therefore, massive nectar production is unlikely to place a strain on plants, unless water is scarce. Finally, it is possible that birds may provide a service in addition to pollination, they may protect the plant from herbivorous insects.

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