Salt intake and regulation in two passerine nectar drinkers : whitebellied sunbirds and New Holland honeyeaters

Show simple item record Purchase, Cromwell Nicolson, Sue W. Fleming, Patricia A. 2013-04-10T07:00:25Z 2013-04-10T07:00:25Z 2013-05
dc.description.abstract Avian nectarivores face the dilemma of having to conserve salts while consuming large volumes of a dilute, electrolyte-deficient diet. This study evaluates the responses to salt solutions and the regulation of salt intake in whitebellied sunbirds (Cinnyris talatala) and New Holland honeyeaters (Phylidonyris novaehollandiae). Birds were first offered a choice of four sucrose diets, containing no salt or 25, 50 or 75 mM NaCl. The experiment was repeated using five sucrose concentrations (0.075 to 0.63 M) as the base solution. Both species ingested similar amounts of all diets when fed the concentrated base solutions. However, when birds had to increase their intake to obtain enough energy on the dilute sucrose diets, there was a general avoidance of the higher salt concentrations. Through this diet switching, birds maintained constant intakes of both sucrose and sodium; the latter may contribute to absorption of their sugar diets. A second, no-choice experiment was designed to elucidate the renal concentrating abilities of these two nectarivores, by feeding them 2 0.63 M sucrose containing 5-200 mM NaCl over a 4 h trial. In both species, cloacal fluid osmolalities increased with diet NaCl concentration, but honeyeaters tended to retain ingested Na+, while sunbirds excreted it. Comparison of Na+ and K+ concentrations in ureteral urine and cloacal fluid showed that K+, but not Na+, was reabsorbed in the lower intestine of both species. The kidneys of sunbirds and honeyeaters, like those of hummingbirds, are well suited to diluting urine; however they also appear to concentrate urine efficiently when necessary. en
dc.description.librarian am2013 en
dc.description.librarian ab2013
dc.description.sponsorship This project was funded by the National Research Foundation of South Africa, the University of Pretoria and the Australian Research Council. The Gauteng Directorate of Nature Conservation granted permits to capture and house the sunbirds, and the Australian Department of Environment and Conservation approved our use of honeyeaters. All animal care procedures and experimental protocols adhered to institutional regulations of Murdoch University (R1137/05) and the University of Pretoria (EC013-07). en
dc.description.uri en
dc.identifier.citation Purchase, C, Nicolson, SW & Fleming, PA 2013, 'Salt intake and regulation in two passerine nectar drinkers : whitebellied sunbirds and New Holland honeyeaters', Journal of Comparative Physiology :B Biochemical, Systemic, & Environmental Physiology, vol. 183, no. 4, pp. 501-510. en
dc.identifier.issn 0174-1578 (print)
dc.identifier.issn 1432-136X (online)
dc.identifier.other 10.1007/s00360-012-0722-3
dc.language.iso en en
dc.publisher Springer en
dc.rights © Springer-Verlag Berlin Heidelberg 2012 en
dc.subject Salt balance en
dc.subject Nectarivores en
dc.subject Renal function en
dc.subject Osmoregulation en
dc.subject.lcsh Salt in animal nutrition en
dc.subject.lcsh Birds -- Effect of salt on en
dc.subject.lcsh Sunbirds en
dc.subject.lcsh Honeyeaters en
dc.subject.lcsh Passeriformes en
dc.title Salt intake and regulation in two passerine nectar drinkers : whitebellied sunbirds and New Holland honeyeaters en
dc.type Article en

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