Solution acceptance by common ravens (Corvus corax) given two-bottle preference tests

Two-bottle tests of solution acceptance were conducted in an outdoor aviary with eight common ravens (Corvus corax). Aqueous concentrations of the following chemicals were used: five common sugars, three salts, two acids, quinine hydrochloride, and sodium saccharin. Solution acceptance, as recorded for the different ravens on each test, was the percentage of preference shown for a test solution over water (comparison solution). Mid-range saccharin concentrations (0.10% to 0.80% [w/w]) were preferred over water in the tests. The preference for saccharin contrasts with all other reports on avian response to the chemical in two-bottle tests. Nonetheless, the ravens nonpreferentially accepted lower concentrations or were averse at higher concentrations to drinking sugar solutions. Similar, though more sharply marked, shifts from indifference to aversion were noted in tests with the other chemicals. The possible relevance of these latter findings to the food habits of ravens is discussed.