Salt intake and regulation in two passerine nectar drinkers: white-bellied sunbirds and New Holland honeyeaters

摘要: Avian nectarivores face the dilemma of having to conserve salts while consuming large volumes a dilute, electrolyte-deficient diet. This study evaluates responses salt solutions and regulation intake in white-bellied sunbirds (Cinnyris talatala) New Holland honeyeaters (Phylidonyris novaehollandiae). Birds were first offered choice four sucrose diets, containing no or 25, 50 75 mM NaCl. The experiment was repeated using five concentrations (0.075–0.63 M) as base solution. Both species ingested similar amounts all diets when fed concentrated solutions. However, birds had increase their obtain enough energy on dilute there general avoidance higher concentrations. Through this diet switching, maintained constant intakes both sodium; latter may contribute absorption sugar diets. A second, no-choice designed elucidate renal concentrating abilities these two nectarivores, by feeding them 0.63 M 5–200 mM NaCl over 4-h trial. In species, cloacal fluid osmolalities increased with concentration, but tended retain Na+, excreted it. Comparison Na+ K+ ureteral urine showed that K+, not reabsorbed lower intestine species. kidneys honeyeaters, like those hummingbirds, are well suited diluting urine; however, they also appear concentrate efficiently necessary.