Preferences of cedar waxwings in the laboratory for fruit species,colour and size: A comparison with field observations

Fruit preferences of cedar waxwings, Bombycilla cedrorum, in the laboratory were compared with preferences in the field to identify fruit characteristics that influence choice by avian dispersers. Waxwings ate 12 of 13 species of fruits offered individually in laboratory tests, but in the field ate only eight of the same 13 species. When given a choice of 10 fruit species offered simultaneously, waxwings showed a strong preference for fruits that were small or red. Preferences for fruit species in the laboratory were not correlated with morphological or nutritional characteristics of the fruits. When offered food that differed only in colour, waxwings initially preferred red over blue, yellow and green. In later tests, preference for red fruit was less marked. In tests for size preference, waxwings preferred small pieces of fruit (6 mm) over medium pieces (9 mm), and medium pieces over those that were large (12 mm). Sizes of fruits preferred in the field and in the laboratory tests were approximately 6·0–7·5 mm. Thus, waxwings can discern differences in food items and they have definite preferences. The lack of complete agreement between preferences for fruits in the field and in the laboratory suggests that factors important in the field but controlled in the laboratory (e.g. abundance, location) override preferences for certain fruits. However, some fruit characteristics, particularly size, were consistently influential in the laboratory and in the field.