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Abstract

There are many social and sexual contexts in which individuals should base their interactions with others on the recipient's history of behaviour or morphology over the time in which the two have associated. I tested the ability of female zebra finches to discriminate among males on the basis of their past as well as current phenotype by allowing them to view groups of four males for two hours a day, for four days, while the bill colour of individual males was manipulated with orange and red paint. Four bill colour treatments were assigned to the males in a stimulus set. One male was orange for all four days, one was red for all four days, a third male was orange for the first two days but red for the second two days, and the fourth male was red for the first two days and orange for the second two days. There was a slight, but non-significant, preference for orange bills when compared on a day to day basis regardless of bill colour history. However, when males were ranked on day 3 and day 4 according to the proportion of the assessment period they had been orange, there was a significant positive correlation between preference on those days and proportion of time orange. A more detailed examination shows that there was an effect of bill colour history independent of current bill colour but not vice-versa. These results suggest that discrimination is based not only upon instantaneous appearance, but average appearance over the assessment period.