100.5 Saturday, Jan. 7 Can sugar preferences in Australian birds be explained by behaviour or physiology? NAPIER, K.R.*; XIE, S.; MCWHORTER, T.J.; NICOLSON, S.W.; MARTINEZ DEL RIO, C; FLEMING, P.A.; Murdoch Univ., Western Australia and Univ. of Wyoming, Laramie; Murdoch Univ., Western Australia; Murdoch Univ, Western Australia and Univ. of Adelaide, South Australia; Univ. of Pretoria, South Africa; Univ. of Wyoming, Laramie; Murdoch Univ, Western Australia email@example.com
Diet preferences may reveal a great deal about the digestive physiology of birds and their relationship with food sources, by reflecting physiological constraints and therefore mechanisms of digestion. We assessed the interaction between diet concentration and sugar-type preferences of four nectarivorous species (red wattlebird, rainbow lorikeet, New Holland honeyeater, singing honeyeater) and two frugivorous species (silvereye, mistletoebird). Each individual bird was offered paired energetically-equivalent diets: a sucrose solution and hexose (1:1 mixture of glucose:fructose) solution over a range of diet concentrations from 0•075 to 2 mol/L Sucrose Equivalents (SE). All species demonstrated a preference for hexose over sucrose on dilute diets and sucrose (or no) preference on concentrated diets, but differed in terms of when this preference switch took place. One physiological constraint that may influence a preference for hexose solutions on dilute diets is the level of intestinal sucrase activity, which we assessed in five of the six study species. Sucrase activity was lowest in birds that displayed a significant hexose preference for a higher range of diet concentrations, suggesting the degree of sucrase activity may determine hexose preference. Sucrose preference at higher concentrations may possibly be explained by taste perception due to differences in solution osmolality, or may reflect a degree of imprinting due to experience with natural nectar compositions.