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

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-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. Received 30 September 1994, accepted 15 April 1995. CEDAR WAXWINGS (Bombycilla cedrorum) normally have a yellow terminal band on their tails. Within the past 35 years, Cedar Waxwings with orange tail bands have appeared in the northeastern United States and southeastern I Present address: Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071, USA. E-mail: waxwing@uwyo.edu Canada (Yunick 1970, Hudon and Brush 1989, Pittaway 1991, Mulvihill et al. 1992). Carotenoid pigments (i.e. xanthophylls) cause the yellow tail bands of Cedar Waxwings (Hudon and Brush 1989), as well as the red tips of their secondaries (Brush and Allen 1963). The coloration of the novel orange-tipped rectrices of Cedar Waxwings is caused by the inclusion of a red carotenoid pigment (rhodoxanthin) in the FRONTISPIECE. Tail colors of Cedar Waxwings. Bird in upper left (Bird 1) was fed only Lonicera fruits during tail molt. Bird in upper right (Bird 2) was switched from Lonicera fruits to chow diet midway through tail molt. Bird in lower left is wild bird with orange tail band (Cornell University Vertebrate Collection [CVC] no. 30194; juvenile male, 9 November 1961, Chemung Co., New York). Bird in lower right is wild bird with normal yellow tail band (CVC no. 14422, adult male, 1 June 1942, Tompkins Co., New York).