Thresholds for sweet, salt, and sour taste stimuli in cockatiels (Nymphicus hollandicus)

Little is known about avian taste perception and how taste affects food cho ice. We designed a study to determine the concentrations of aqueous solutio ns of common chemical taste stimuli that result in altered consumption patt erns. Using two-choice taste-preference tests, we studied the taste thresho lds of caged cockatiels (Nymphicus hollandicus) for aqueous solutions of po tassium chloride. a phosphate buffer (to test pH), fructose, and glucose. F irst, the preferred and nonpreferred bottle locations were determined for e ach bird. Then, depending on the compound, the rest solutions were placed i n bottles in either the preferred or the nonpreferred locations and water w as placed in the opposite bottle. Four parameters were measured at the end of 3-day test periods (total consumption. consumption from water side, cons umption from test solution side, and proportion of nonpreferred side consum ption to total consumption). Experiments were repeated with increasing conc entrations of test flavors until intake variables were significantly affect ed (P < 0.05). Cockatiels distinguished (P < 0.05) between purified water a nd 0.16 mol L-1 potassium chloride, 0.40 mol L-1 fructose, or 0.16 mol L-1 glucose. The test birds did not distinguish between water and 0.05 mol L-1 mono- and dibasic sodium phosphate buffer solution at any tested pH within the range of 4.9-7.7. When these findings are compared to previous experime nts with the same birds, it becomes dear that the gustatory reactions of co ckatiels for two different stimuli (e.g., NaCl and KCl) from the same gener al taste category (salt, sweet, sour) can vary widely. This variation in th e responses to related stimuli could be the result of a number of factors i ncluding anion effects (for salts and acids) as well as nongustatory physio logical processes (e.g., as renal control of blood osmolarity). (C) 2001 Wi ley-Liss, Inc.