Nectar concentration preferences and sugar intake in the white-bellied sunbird, Cinnyris talatala (Nectariniidae).
Plant nectar is a simple food consumed by many different animals. Preferences regarding its components, especially sugars, have been studied for many species, but the preferences of nectar-feeding birds for different sugar concentrations are less well known than their sugar type preferences. The concentration preferences of white-bellied sunbirds, Cinnyris talatala, were examined using paired solutions of either sucrose or equicaloric 1:1 mixtures of glucose and fructose. Preferences were tested over a broad concentration range of 0.25-2.5 M sucrose equivalents (using 0.25 or 0.5 M differences between pairs). On both sucrose and hexose diets, the higher concentration was preferred up to 1 M, but there were no significant preferences above this concentration, except that birds preferred 1.5 to 2 M sucrose. As with other nectar-feeding vertebrates, the laboratory preferences of sunbirds do not explain the low concentration of their natural nectars. We recorded apparent excess sugar consumption during 6 h preference tests involving concentrated hexose diets; this could be due to digestive constraints or viscosity differences between sucrose and hexose solutions.
Leseigneur
C D C
CD
Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
Nicolson
S W
SW
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D005260:Female; D005518:Food Preferences / Q000502:physiology*; D005632:Fructose / Q000008:administration & dosage; D005947:Glucose / Q000008:administration & dosage; D008297:Male; D009994:Osmolar Concentration; D046109:Passeriformes / Q000502:physiology*; D053147:Plant Exudates / Q000008:administration & dosage*; D013019:South Africa; D018709:Statistics, Nonparametric; D013395:Sucrose / Q000008:administration & dosage
D004040:Dietary Carbohydrates; D053147:Plant Exudates; D005632:Fructose; D013395:Sucrose; D005947:Glucose