No abstract

New Holland honeyeaters collect nectar, manna or honeydew for energy and hawk small flying insects for protein. The insects taken were usually Diptera and Hymenoptera weighing 0.7 mg dry weight or less. Net rates of energy gain from hawking small flying insects were usually less than 20 J min~' and sometimes negative and insufficient to meet the bird's daily energy requirements. Those from feeding on nectar, manna or honeydew were usually above40J min~^ andoftenabove400J min~^ atdawn and the birds depended on these carbohydrates for energy. Nectar, manna and honeydew contained negligible amounts of protein, and the birds used small flying insects as sources of protein, and presumably other nutrients. Given that carbohydrate resources supply better rates of energy gain than insects. New Holland honeyeaters should collect their energy requirements from carbohydrates and only collect sufficient insects to satisfy their protein requirements. Estimates of the food intakes of both non-breeding and breedig birds showed that they did this. Non-breeding New Holland honeyeaters collected from 72 to 125 (mean 92) kJ of carbohydrates per day and 17 to 58 (mean 31) mg of protein per day. These meet the daily energy (75 kJ) and protein (20 mg) requirements of the birds. Breedig birds collected more carbohydrates and more insects, but in proportion to their increased energy and protein requirements respectively.

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 flowerfeeders 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, 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. Flowers 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 oron 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 birdpollinated 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.