SAMPLING AND INFORMATION ACQUISITION BY WESTERN SCRUB-JAYS, APHELOCOMA-CALIFORNICA

Animals often make choices based on cues that provide uncertain inform ation about the value of alternative options. To examine how this unce rtainty affects sampling behaviour, western scrub-jays were studied in the field during selection of single food items to scatter-hoard. Nin e habituated birds were videotaped at feeders during repeated presenta tions of pairs of unshelled peanuts that varied in size. Jays initiall y scanned the peanuts before picking one up and in 38% of trials handl ed both, often switching repeatedly between them before making a choic e. The jays preferred heavier nuts, which contained a larger food rewa rd, but made errors particularly when mass differences were small. In addition, when choosing which nut to pick up first the birds discrimin ated mass relatively less accurately when the peanuts were larger. Whe n mass differences were small the birds were more likely to handle bot h nuts before choosing. Handling both nuts raised the probability of s electing the heavier one by 20%, but did not increase the rate of food acquisition above that obtainable by scanning because it also increas ed time spent choosing. These results confirm recent suggestions that animals facing difficult discriminations may increase the accuracy of choice by sampling additional cues. (C) 1998 The Association for the S tudy of Animal Behaviour.