A Field Study of Winter Fruit Preferences of Cedar Waxwings

Winter field censuses of Cedar Waxwings (Bombycilla cedrorum) in an urban area of central Oklahoma were used to evaluate which fruit characteristics influence avian choice. Abundance estimates (g/ha) of fruits of each species in the study area were made to determine the resource base available to waxwings. I hypothesized that waxwing foraging preferences would be correlated with one or more of the following fruit characteristics: (1) abundance, (2) color, (3) size, (4) height, (5) pulp-to-seed ratio, (6) percent water, (7) percent protein, and (8) caloric content. Preliminary data from 1983-1984 indicated that waxwings were selective; they ate mostly mistletoe (Phoradendron serotinum) and one species of a relatively small crab apple (Malus sp.) from the 16 species available. During the winter of 1984-1985, waxwings used mistletoe heavily, along with hackberry (Celtis sp.), until these species were mostly depleted. Yaupon and deciduous hollies (Ilex vomitoria and I. decidua) then were used heavily and became the most important overall food sources during the winter. Waxwings generally ate abundant species and seldom ate rare ones. Among the fruits consumed, the order of waxwing preference was related only to fruit abundance, size, and caloric content. Comparisons of the results with other studies of frugivorous birds shows only partial agreement on the fruit characteristics most influential in avian choice, suggesting that a number of factors interact to determine foraging preferences and that these factors are not constant for all frugivorous species.