Taste Preferences, Color Preferences, and Flower Choice in Hummingbirds

Abstract

Taste and color preferences have been experimentally demonstrated for a variety of birds, and the literature on food habits of wild birds is enormous, but as yet there is little to tie the two together. Laboratory experiments have usually involved taste stimuli that are probably irrelevant to birds in the wild; and the taste stimuli presented by insects, seeds, fruit, etc. are complex and difficult to duplicate for experimental purposes. The same is true to a considerable extent of color: the mostly granivorous species studied so far probably never experience bright, monochromatic colors in connection with feeding. Moreover, caloric parameters of birds’ foods are often difficult to measure or estimate but will almost certainly affect food selection, making taste and color preferences harder to assess. Hummingbirds are ideal subjects in studies of taste and color preferences. Their main foods are nectar and insects; flowers are visited almost exclusively for nectar, insects being captured elsewhere. Flower nectar is essentially an aqueous solution of 3 common sugars (Percival 1961, see also beyond). It can be easily sampled and its concentration, caloric value, and composition measured. The taste stimuli can be readily duplicated and manipulated experimentally. Assimilation of flower nectar is essentially 100% (Hainsworth 1974) making caloric parameters easy to estimate. Flowers visited by hummingbirds are usually brightly colored and fairly unpatterned, also favoring experimentation. The long controversy over the existence of color preferences in hummingbirds was reviewed by Grant and Grant ( 1968). The roles of color and taste factors have been greatly clarified by the feeding station experiments of Collias and Collias (1968); similar experiments by Miller and Miller (1971) further elucidated the role of position. These studies suggest a hierarchy of factors influencing feeder choice: sugar concentration and/or taste over position over color. As yet this hierarchy has not been subjected to experimental verification, or applied in detail to flower choice in the field. This paper presents laboratory experiments on taste and color preferences of the Anna Hummingbird (Calypte anna) and several other species. I also present the results of extensive field observations on flower choice by hummingbirds, and consider the taste and color stimuli presented by those flowers visited by hummingbirds. Hopefully, comparing the results of field and laboratory studies will permit a more realistic evaluation of the role of taste and color preferences in food choice by hummingbirds, and a better understanding of the coevolution of hummingbirds and the flowers they pollinate.