HANDLING EFFICIENCY AND BERRY SIZE PREFERENCES OF CEDAR WAXWINGS

In a series of feeding trials, Cedar Waxwings (Bombycilla cedrorum) pr eferred blueberries (Vaccinium spp.) having a mean diameter of 7.5 mm when the diameter of alternative berries exceeded 12 mm. Waxwings did not exhibit clear preferences among blueberries that differed by less than or equal to 3.5 mm mean diameter. For 7.5 mm fruit, observed hand ling times averaged 2.8 sec and increased exponentially as berry diame ter increased. Because the frequency of dropped fruit also increased w ith fruit size, the birds' rate of sugar ingestion was maximized by fe eding on the 7.5 mm berries. The rate of sugar ingestion decreased lin early as blueberry size increased. Thus, within the range of sizes tes ted, Cedar Waxwings preferentially selected blueberries that were more efficiently handled and that produced the highest rate of sugar intak e.