Nectar as food for birds: the physiological consequences of drinking dilute sugar solutions |
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Authors: | S W Nicolson P A Fleming |
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Institution: | (1) Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa, ZA |
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Abstract: | Nectarivory has evolved many times in birds: although best known in hummingbirds, sunbirds and honeyeaters, it also occurs
on an opportunistic basis in a varied assortment of birds. We present a phylogenetic analysis of the distribution of nectarivory
in birds. Specialised avian nectarivores are generally small, with an energetic lifestyle and high metabolic rates. Their
high degree of dependence on nectar as a food source has led to convergence in morphological, physiological and behavioural
adaptations. We examine the constituents of nectar which are most important to bird consumers, and how the birds deal with
them in terms of physiology and behaviour. There are still unanswered questions: for example, the dichotomy between sucrose-rich
nectars in hummingbird-pollinated plants and predominantly hexose-rich nectars in sunbird-pollinated plants appears to have
little to do with bird physiologies and may rather reflect patterns of nectar secretion.
Received November 28, 2002; accepted January 26, 2003
Published online: June 2, 2003 |
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Keywords: | : Nectarivory pollination hummingbirds sunbirds sugar digestion water balance osmoregulation |
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