Consequences of an Alien Shrub on the Plumage Coloration and Ecology of Cedar Waxwings

Cedar Waxwings (Bombycilla cedrorum) with orange (instead of the normal yellow) tail bands have appeared in eastern North America in the last 35 years. Biochemical studies have implicated a dietary cause (Hudon and Brush 1989), specifically the fruits of Lonicera morrowii (Brush 1990), for this novel color variant. I show that rectrices replaced while Cedar Waxwings are feeding on L. morrowii fruits develop orange tips. Rectrices replaced subsequent to switching the diet of molting waxwings from L. morrowii fruits to dog chow were yellow, showing close temporal correspondence between dietary input of rhodoxanthin and the coloration of growing feathers. In the Ithaca vicinity, fruits of L. morrowii are eaten by wild Cedar Waxwings from June until mid-October. The extended pattern of availability and consumption of Lonicera in this region appears to explain my unique observations of adult Cedar Waxwings growing orange tails during the fall months. Cedar Waxwings maintained body condition and molted while on an extended diet of L. morrowii fruits (36 days for two birds and 64 days for two others). Three birds initiated tail molt while on this diet, including one that molted all of its flight feathers. These results emphasize the nutritional specialization of Cedar Waxwings to a diet of sugary, low-protein fruits, and show that molt occurs in an apparently normal manner when birds are eating a low-protein fruit diet.